Cocktail Party Physics

there's still science to do!

A little music, a little animated typography, a little song about the perils of science.

/sarcasm

REPOST: pardon my reverb

Note from your errant blogger(s): Life is currently kicking our collective asses, both professionally and (for some of us) personally, hence the eerie quiet of late at the cocktail party. So much cool stuff, so little time to blog about it! For my part, I've just finished copy-editing The Calculus Diaries manuscript, and am heading off to the San Diego Science Festival, where I will be on a panel on science and science fiction (with David Brin and Scott Sigler, no less!). But I've been blogging for enough years now, that some of you may have missed cool posts from yesteryear. So to tide you over until I get back to blogging this weekend, here's one of my favorite early posts, on concert hall acoustics, inspired by a Jordi Savall performance. And hey, if you hunger for fresher fare, I'm still blogging over at Discovery News.

Back in March, I visited my beloved New York City, having snagged tickets to see a concert performance by the incomparable Jordi Savall, world-renowned master of the viola da gamba and two-time Grammy nominee, whose soundtrack for the French film Tous Les Matins du Monde has sold more than a million copies worldwide. For this event, Savall performed with the Hesperion XXI ensemble and La Capella Reial de Catalunya, both of which he founded. Jen-Luc Piquant is as big a fan of Jordi Savall's music as I am, and we were thrilled at the opportunity not only to hear him perform live, but also by the featured pieces: early Renaissance and Baroque compositions from the Iberian Peninsula region. These are unusual, little-known compositions that Savall has taken upon himself to revive and introduce to classical audiences around the world.

A bit of history: the first Jesuit missionaries in Brazil and Paraguay adapted traditional Amerindian melodies of that region to Christian doctrinal texts translated into the local languages. They even recruited local musicians to take part in the ceremonies, clad in their native garb and playing their own culture's instruments. Inevitably, the two musical traditions merged, combining (according to the program notes) the "European model system, formal structure and contrapuntal techniques... with their own melodic and rhythmic patterns," particularly those associated with native dances. This resulted in some odd, yet affecting hybrids, such as Juan Garcia de Cespedes' Ay qye me abraso -- literally, "I am burning." It features a rhythm based on a popular Mexican dance. The secular aspect is offset by the lyrics: the characters are "panting and sighing because of the excessive heat generated by their emotions at the sight of the newborn Christ." Our own more sonorous, politely composed Christmas carols seem downright emotionally tepid in comparison.

If only the organizers of the event had paid more attention to the venue, the evening would have been an unqualified success. There's no shortage of performance spaces in Manhattan, after all, with decent enough acoustics for this type of music -- the gloriously Gothic St. John the Divine would have been ideal. Alas, the concert was held at St. Paul the Apostle on the Upper West Wide, a small Romanesque-style house of worship whose architectural details added up to a veritable acoustical "perfect storm." Unless one happened to be sitting in the first few rows, the sound was muted, muddy, and each separate part of the complex compositions seemed to reach the audience at different times, so that the percussion always seemed a few beats behind the singers, and/or the instruments. 

Needless to say, the evening was an unmitigated disaster. Several audience members left in disgust, and those who remained to the bitter end were forced to wander forlornly about the sanctuary in hopes of finding one of the "live" spots where the acoustics weren't quite so ruinous. Since it was impossible to fully appreciate the performance, our little group instead found ourselves discussing the scientific aspects of what might be happening to cause the horrific effects.

Composers have always recognized the importance of the acoustics of a given performance space, and many tailored the music they composed to fit those spaces. For instance, Gregorian chants fare well in medieval cathedrals, known for long-reverberation times; ditto for organ music, such as Bach's "Toccata in D Minor." In contrast, Mozart and Haydn composed music to be played in highly furnished chambers, for smaller, intimate audiences. Such pieces lose their clarity when played in highly reverberant spaces. But no one really thought about how to design a concert hall or opera house to achieve optimal acoustics; it was done through trial and error, with little acoustical theory to provide much of a framework to centuries of experiment.

The father of modern architectural acoustics is an American physicist named Wallace Clement Sabine. In 1895, he was a lowly faculty member of Harvard's physics department, who was handed the knotty problem of improving the infamously bad acoustics of the university's Fogg Lecture Hall, part of the recently constructed Fogg Art Museum. Sabine didn't have any particular expertise with sound -- he didn't even hold a PhD (the horror!) -- but he doggedly tackled the challenge  as he would any other physics experiment. He spent several years studying the acoustical qualities both the museum's lecture hall, and the Sanders Theater, widely considered to have excellent acoustics, in order to determine  what might be causing the difference in sound quality.  Specifically, he was attempting to find some objective formula or standard by which to measure and assess the acoustics of performance space designs.

It wasn't an easy task because so many variables had to be taken into consideration. He and his assistants tested each space repeatedly under varying conditions, moving materials back and forth between the two halls -- such as hundreds of seat cushions from the Sanders Theater -- and making careful measurements armed only with an organ pipe and a stop watch. He timed how long it took for different frequencies of sounds to decay to inaudibility under those varying conditions: with and without Oriental rugs, various numbers of people occupying the seats, and so forth.

Ultimately, he was able to determine that there was a definitive relationship between the quality of a room's acoustics, the size of the chamber, and the amount of absorption surfaces that were present. And he came up with the formula for calculating reverberation time, still the critical factor for gauging a space's acoustical quality.

Sabine concluded that the Fogg Lecture Hall's reverberation time was too long -- a spoken word would remain audible for 5.5 seconds, as opposed to the optimal reverberation time of 2.25 seconds -- so there was too much resonance and echo. He solved the problem by outfitting the space with sound-absorbent materials to reduce the "echo effect." His success cemented his reputation and he went on to serve as acoustical consultant for the design of Boston's Symphony Hall, still considered one of the best halls in the world in terms of sound quality. And oh, yes: the unit of sound absorption, the sabin, was named after him.

The field of concert hall acoustics has advanced far beyond Sabine's rudimentary first measurements, although there are still purists who believe that there will always be a subjective element that eludes attempts at strict mathematical description. Nonetheless, using just those sorts of quantifiable tools, Leo Beranek, one of the most eminent acoustic engineers, has identified three basic aspects to achieving a sufficiently good sound in a concert hall: (1) Listeners should be as close to the orchestra as possible; (2) Listeners should have a line of sight to the orchestra so the sound can travel unobstructed; and (3) the interior surface of the hall should be made of a hard material so that sound energy is not absorbed or lost. So an acoustical consultant needs to balance strength, reverberation and clarity requirements when designing a performance space.

Computer modeling has become one of the modern acoustician's most important tools. It turns out that the sound diffusing through a performance space can be modeled as particles of light bouncing around that space, much like a billiard ball bounces around a table in response to being hit by the cue. Acousticians can use those models to calculate the impulse response of the sound. Once the sound field of a modeled space has been determined, it's possible to simulate the sound as it would appear within the real space -- a technique called auralization, the acoustic equivalent of visualization techniques. Auralization software can help acoustical consultants predict, and perfect, how a proposed peprformance space design will sound, based on a wide range of parameters: room size and shape, surfaces, and materials, among other design features.

Auralization is still in its infancy when it comes to concert hall acoustics, but a team of Korean scientists has developed a way to paint "sound pictures" in space: specifically, a technique for controlling the sound in a selected region of listening space. They compare it to painting a picture on a canvas using "acoustical paintbrushes." They mix and overlap sound strokes by playing multiple loudspeakers simultaneously to create interference effects. The end result is a "photocopy" of, for example, a symphony hall's sound picture. The technique is called sound field reproduction.

Getting back to that infamous Savall concert: there were clearly many different factors at work on the night of the botched acoustics. For instance, different musical styles require different reverberation times. If reverberation time is too long, the notes blend together too much, so that it becomes difficult to distinguish individual notes in fast, complex passages. I had been especially looking forward to hearing my first villancico: a religious song performed in the vernacular, incorporating percussive African dance rhythms and a highly theatrical call-and-response effect between soloists and the chorus (tutti). All the pieces that night featured quick tempo changes, unusual rhythms and complex vocal combinations. Throw in the odd percussionist and a woman with castanets and high heels stomping her way through some of the pieces to add even more of a staccato beat, and the result was a hopeless muddle of reflected sound -- because of an overly long reverberation time.

The shape of the performance space plays a vitally important role in all of this, because it affects how sound is distributed in that space. Fan-shaped halls, favored for theaters and early cinemas, lack sufficient side reflections to achieve good sound quality (specifically, the pleasurable sensation of being "enveloped" in the music), while the circular and elliptical shapes favored by many architects tend to focus sound on certain "hot spots," leaving much of the remaining space acoustically "dead." St. Paul the Apostle's main sanctuary features a long gallery topped by a high curved roof -- I believe the technical term is a "barrel vault" -- lined on both sides by decorative archways. I'm not sure if that qualifies as a "shoe box" shape, but the poor acoustics would indicate that it is not. Making matters worse, the floor is mostly wood, with marble tile borders, so too much sound is absorbed. Add in poor line of sight, and you've got that muted, muddied quality to the music in question.

Frankly, the performance by Savall's ensemble du jour would have been better served if it had been given in the subway station. There's a reason so many buskers favor specific spots in New York City's vast subterranean transit network. Alex Case, director of Fermata Audio and Acoustics in Portsmouth, New Hampshire, has conducted extensive studies of local musicians who play regularly in subway stations. I interviewed Case -- who wears a second hat as a professor at Berklee College of Music in Boston -- back in 2004 during a meeting of the Acoustical Society of America about his NYC subway work. Basically, he recorded numerous subway "performances" with portable digital recorders and then analyzed the data he'd collected.

The walls of those stations are made of rigid heavy materials like tile, stone, steel and concrete, all of which are better at reflecting sound waves. This allows sound pressure (volume) to build up naturally, with no need for extra amplification -- that all-important reverberation. The same sound, heard up close, has much less reverberation. (This is also the same reason why so many people enjoy singing in the shower.) In fact, Case likes to mention that there's a very famous tile-and-concrete stairwell outside a professional recording studio in Manhattan that serves as an excellent "reverberation chamber" and has featured on several classic rock recordings.

Not surprisingly, he found that those stations with acoustical qualities in keeping with the established numerical criteria embraced by professional sound consultants, also proved most popular with street musicians. For instance, buskers instinctively seek out locations near hard walls and under low ceilings to amplify their music above the routine din. They also tend to avoid stations with lots of announcements, or major transfer hubs, since there are too many trains running through the station to provide enough time for an extended performance period.

Of course, the very qualities that make subway stations so good for the street musicians can also be blamed for the notorious incomprehensibility of the routine service announcements over the MTA's public address system. (Jen-Luc Piquant firmly believes the audibility of such pronouncements is inversely proportional to the importance of any given announcement.) Amplifying speech requires far less reverberation than music. What sustains musical notes by building up sound reflections causes speech to become mushy and unintelligible. The reflections all mix together so that individual words can't be deciphered. Add in the electronic amplification, and it's little wonder the announcer sounds like he/she is speaking with a mouthful of marbles.

We love subway buskers, and we love Alex Case for choosing to study the acoustics of those performances rather than (or in addition to) the more hoity-toity, elitist performance spaces -- conventional opera houses and symphony halls, for example, which are quite nice in their own right, don't get me wrong. They just exclude a large percentage of the population. Case loves the broad accessibility of the subway, pointing out that some 7 million people ride the NYC subway system every day. Even if only 1 in 10 passengers pay attention to the music, that still adds up to about 700,000 listeners per day, from every conceivable social demographic. In comparison, Carnegie Hall and Lincoln Center, combined, would have to sell out 54 shows every day, on all six main stages, just to compete. So the subway is the concert hall of the huddled masses.

Savall himself has something of Case's "common touch." The Spanish and Portuguese composers featured in the program that night combined high and "low" art, seeking to embrace the "pop culture" of their time. This might explain why there were so many young people in the audience. Classical musical aficionados are constantly bewailing the absence of youth in their audiences. Perhaps it's because the mainstream programs are so predictable: great music, yes, but always the same pieces by the same composers. This isn't an approach likely to appeal to younger, hipper audiences, who are far more likely to gravitate towards fresh alternatives, such as lost or rediscovered historical gems from, say, the 10th to the 18th centuries. That's Savall's specialty. His bio in the program notes offers his success as "proof that early music does not have to be elitist or of interest only to a minority, and that it can and indeed does appeal to an increasingly large and young audience." Savall is making classical music cool.

On the way out after the performance, I picked up a church bulletin, hoping to glean a little information about the building's history and design. Mostly it contained the usual church announcements, but on page 2 there was an item about the new sound system being installed in the sanctuary to address the chronic acoustical problems. It made mention of the need to eliminate certain "dead spots" in the sanctuary, not to mention increasing clarity in the spoken word in the nave. (The church leaders declined, however, to carpet the marble floors and stone pillars to better absorb sound to eliminate the echo effect completely, purely for aesthetic reasons.) Given the fact that Savall is such a terrific ambassador for early music, in addition to being a world-class musician, it's doubly appalling that the organizers would deliberately book his ensemble in such a well-known acoustically challenged space. Yes, it was malice aforethought. Savall et al deserved better. And so did his audience.

all in the family

Jen-Luc Piquant was tres desole in mid-August when she learned (via The Perfect Silence) that pioneering violin maker/acoustician Carleen Maley Hutchins had died at age 98. For those who follow the acoustics of musical instruments, and violins in particular, Hutchins was a legend -- unorthodox, innovative, and completely unapologetic about her work, which occasionally met with skepticism, if not outright hostility. As Margalit Fox wrote in the New York Times obituary for Hutchins: "Working intently and noisily in her home in Montclair, NJ, she helped reimagine the idea of what a violin could be. In the process she designed and built an entire family of violins, eight instruments proportional in size and pitch known collectively as the new violin family or the violin octet." The eponymous Hutchins Consort performs exclusively with her instruments.

My favorite description of her personality comes from Gabriel Weinreich, a professor of physics/acoustician at the University of Michigan: "No respect for authority; a long attention span; scrupulous honesty; enthusiasm for intellectual collaborations; and the willingness to spend a lifetime beating a path through the jungle." I had the honor of interviewing Hutchins (then a spry 94) by phone at her New Hampshire home in 2005 for the American Institute of Physics' Inside Science News Service, and Weinreich's description fits my impressions of her. I never did get around to meeting her in person, which I regret.

It's the no respect for authority and stubborn perseverance that impressed me most: you can't be cowed by the The Man if you're going to be a trailblazing pioneer, and Hutchins had the deck stacked against her from the start. It's easy to forget how far we've come in the last 100 years in terms of women being welcomed in the professional/academic sphere. Hutchins was born in 1911 in Springfield, Massachusetts, grew up in Montclair, New Jersey, and stood out from her peers even as a child. For instance, she loved woodworking and played the trumpet -- both highly uncommon pursuits for girls of that era.

Even more unusually, she attended Cornell University, where she studied entomology and earned a degree in biology in 1933, followed by a master's degree in education from New York University in 1942. This enabled her to land a decent job as a teacher at a private girl's school on Manhattan's Upper West Side. She married chemist Morton Hutchins in 1943, a man who shared her love of woodworking: the couple built their own house together. At the Brearley School, Hutchins made friends with several other faculty members who invited her to join their chamber group. She showed up, trumpet in hand, but it was far too loud for a chamber group. They really needed someone who played the viola. Rather than bow out, Hutchins learned to play the viola, buying an instrument for $75.

While she enjoyed the musical interludes, Hutchins became increasingly frustrated with the limitations of her bargain viola, and asked her uncle, a violin maker, to build her a better one. I guess he didn't want to enable her or something, because instead, he suggested she build one herself -- she did have all that woodworking experience, after all -- and gave her the name of a Russian violin maker in New York City who could help her get started. The Russian man wasn't exactly encouraging, but Hutchins wasn't easily dissuaded. "He didn't think much of a woman making an instrument, but at least he sold me a blueprint and a book and told me how to get started," she told me. And gosh darn it, she succeeded in building her very first viola over the next two years.

From the start, she was serious about the science behind building violins, striking up a long association in the late 1940s with Harvard physicist Frederick Saunders, who studied violin acoustics. She specifically designed instruments he could analyze and pick apart to determine just what gave rise to the distinctive quality sound associated with Stradivari violins, for example. Nor was Hutchins above the occasional scavenging. The New York Times obituary relates my all-time favorite Hutchins story. In 1957, she became enamored of a maple shelf in a phone booth in Columbia University's medical school; it was just the thing for the back plate of a new viola she was building, and she had an "in" at the school: her good friend Virginia Apgar, a doctor at Columbia and herself an amateur maker of violins. As Fox tells it:

One night [Apgar] and Mrs. Hutchins stole into the building with some tools and a replacement shelf stained to match. As Dr. Apgar stood guard, Mrs. Hutchins set to work. To their dismay, the new shelf was a quarter-inch too long. Mrs. Hutchins had a saw and there was a ladies' room nearby. As the New York Times reported afterward, "a passing nurse stared in astonishment at the sounds coming through the door." Dr. Apgar could think quickly. (She had, after all, devised the Apgar score, used worldwide to measure the health of newborns. "It's the only time repairmen can work in there," she said. Spirited out of the hospital, the shelf made a magnificent viola back.

Hutchins excelled at finding the critical balance between two key resonances when making her instruments. First and foremost is the natural wood resonance which can be tuned when the instrument is in pieces; the unattached wooden top and back of the instrument are known as "free plates" during this stage of the process. Traditionally, violin makers would "tune" the plates by carving away the wood underneath to specific thicknesses in order to get the desired natural resonances, flexing the wood plate in his/her hand and tapping them with a fingertip close to the ear to detect the telltale "ring." But it as much an art as a science; Hutchins thought there might be a better, more precise way to tune the plates to the natural resonance, and invented "free plate tuning." She used a loudspeaker to get the plates to vibrate, and spread glitter on top of them, watching where the tiny particles settled in order to find the exact lines that would give her the desired resonances. You can see the process firsthand in this nifty YouTube video featuring Hutchins herself, hard at work, talking about her process and her abiding love for wood:

The other critical resonance for a violin is the air resonance that is produced once the instrument has been assembled. That's the resonance that arises from the body cavity -- kind of like what happens when you blow air across a glass bottle with a narrow neck to produce a tone (and that tone will be higher or lower depending on how much fluid is in said bottle). A violin has two holes that serve a similar purpose. After studying hundreds of master violins, Hutchins and her collaborators concluded that the best resonances always occurred within a very narrow range: the two open middle strings. The D string, second from the bottom, provided the fundamental air resonance, while the wood resonance fell one-fifth higher, on the next highest violin string (violins are tuned in fifths).

Another of Hutchins' innovations came in 1974, when she and collaborator Daniel Haines developed a graphite-epoxy composite to replace the usual spruce wood favored for the top of violin bellies. Choice of wood, and how that wood is treated, has long been a hot area of study by acousticians eager to uncover the "Stradivari secret" -- what gives a Strad that unique quality of sound. (I've written about this topic before here.) Granted, it's a highly subjective analysis -- the BBC organized a blind listening test in 1974, where not even world-famous violinists and violin dealers could all correctly distinguish between a Strad and a modern instrument -- but there does seem to be evidence that treating the wood can enhance an instrument's acoustical qualities.

This was bolstered by the news that made the science headlines a couple of weeks ago during an annual conference in Germany on, um, forest husbandry. Empa scientist Francis Schwarze and a Swiss violin maker named Michael Rhonheimer collaborated on building violins with wood treated with fungus for up to 9 months, and pitted their modern instrument against a Stradivarius in a blind listening test. (Star British violinist Matthew Trusler did the playing honors.) Of the 180 or so people in attendance, 90 chose the fungal violin (dubbed Opus 58) that had been fungally treated for nine months to be the best of the lot, and fully 113 actually thought Opus 58 was the Strad.

Per Horst Heger of the Osnabruck City Conservatory, this could make acoustically superior instruments available to talented young musicians who would never be able to afford their own Strad; now they could have the same tonal quality for less. It all comes down to the quality of the wood, he explains. The fungal attack changes the cell structure of the wood, reducing its density and simultaneously increasing its homogeneity, thereby giving an instrument made with that wood a "warmer, more rounded sound." Antonio Stradivarius might not have benefited from fungus, but he did get help, apparently, from the "Little Ace Age" that hit Central Europe from 1645 to 1715. Trees grew more slowly and uniformly as a result of the longer winters and cooler summers, and that makes for wood with terrific acoustical qualities.

I don't know what Hutchins would say to that, with her instinctive feel for trees and wood. But she knew a little something about re-learning the lessons of the past. One of the most fascinating things she told me back in 2005 was her rediscovery -- while building the first violin octet at the request of composer Henry Brant in the late 1950s -- of lost musical principles once described bby the 17th century German composer Michael Praetorius. (The week Hutchins died, I listened to Praetorius on my morning commute in her honor. It seemed fitting.) Another musically inclined colleague told her about the composer's three-volume treatise, Syntagma Musicum, published in 1619, which detailed musical practices and instruments of the period. 

In particular, Praetorius described an octet family of violins tuned to the same ranges Hutchins was developing. For instance, Hutchins' baritone violin -- similar to a large cello -- featured the same dimension and string length as that pictured in the 17th century text. Ditto for the contrabass violin. "He was writing about something that was common knowledge at the time. That knowledge was lost," she told me. She figured that the tone of these early octets was not up to snuff acoustically, and thus they were replaced when the great 17th century violin makers began building instruments with exquisite resonances ideally suited for the performance needs of the era. Those earlier designs were abandoned, only to be rediscovered over 300 years later by a stubborn violin maker named Carleen Hutchins.

The traditional violin family includes the violin, the viola, and the cello, each different quite a bit in timbre. In contrast, the instruments in Hutchins' octet family range from the seven-foot contrabass to a tiny treble violin tuned a full octave above a standard violin. The sizes are graduated at each half-octave, filling in the gaps in timbre. The result (quoting the New York Times again) is "an even, densely woven tissue of sound, almost like choral music without the words."

An unexpected consequence of the redesign is that the placement of the key resonances shifts in the violin octet instruments. (Fans of the octet claim the instruments correct the acoustic imbalances of traditional violins.) Classical composers wrote music specifically tailored to the strengths of traditional instruments on those key resonances. For instance, Hutchins told me that in Mozart's two-viola quartets placed the first viola through the upper of the two main resonances and the second viola through the lower. With the octet, those resonances shift, which means most classical pieces must be transposed and rearranged before, say, the Hutchins Consort can perform them on this new family of violins. (There are modern composers now writing specifically for the violin octet instruments.)

Similarly, even world-class musicians like cellist Yo-Yo Ma must reacquaint themselves with these new instruments. Ma recorded Bela Bartok's violin concerto using one of Hutchins' alto violins (it has the register of a viola but is played vertically, like a cello), and found he had to play the instrument a bit differently in order to achieve the resonances he needed, for example. Robert Spears, a violin maker who trained under Hutchins (who I also spoke with back in 2005) thinks that the shifted resonances give the octet violins more tonal uniformity across the strings than traditional instruments. "A common complaint among musicians is that as one goes from string to string,  each one can sound like it's on a different instrument," he explained. "Skilled players do a terrific job of minimizing these effects. When suddenly they don't have to compensate for it anymore, it's almost a handicap at first until they realize that particular problem is gone."

Not everyone is a diehard fan of Hutchins' work; I think it's safe to say that she offended her share of colleagues over her long, distinguished career; even her fans would admit she could be abrasive. But even the skeptics admire her fortitude, her perseverance, and there's no doubt she made lasting contributions to the ongoing study of violin acoustics and instrument building. Hutchins herself made seven full octets over the years -- no small feat, since it requires a good 2000 hours to do so. Her "disciples" have built even more. Several of her creations are now housed in museums collections, at the Metropolitan Museum of Art, the Musik Museet in Stockholm, the University of South Dakota, and at the Edinburgh University Collection of Historical Musical Instruments.

The remaining three octets she built are in the capable hands of the Hutchins Consort. Hopefully we can look forward to their continued use in performance (and in the lab). After all, Hutchins said that her instruments "still need to be explored in depth and played seriously by a group of dedicated musicians who will give them the same treatment that is given to learning any stringed instrument." Carleen Maley Hutchins may have shuffled off this mortal coil, but her spirit lives on with the violins she built -- particularly every time they are played.

all you need is the rocket experience

If you've been paying any attention here, you know what a huge supporter of space exploration I am. Manned missions to Mars, moon bases, shuttle flights, space tourism: I love it all. It's probably part of my love of travel; what could possibly be more different from home than another planet? Than outer space? My fascination also stems from an early love of science fiction and early indoctrination with Star Trek (I was 6 when the show first aired). But its simultaneity with the first moon landing (the original series ran from 1966-1969, in case you actually don't know this) was probably the clincher. Not only could we dream about going to other planets, but hey! We could do it! Nothing could be more inspirational to a kid than watching a dream come true, or in this case, watching people actually setting foot on an alien world, when all you've done is read about it or seen fictional stories about it. It gives one a "damn we're good!" feeling not to be rivaled or duplicated in any other way.

 This is one of the reasons I feel shuttle flights are so important: not just for the scientific knowledge that we gain with each one of them, but for their immeasurable inspirational quality. Having lived most of my life with the fact of my fellow humans flinging ourselves recklessly into space from right here at home, I can't imagine that not happening, or imagine having to look to, say, China, for the next exploratory manned rocket launch. I do think space exploration should be an international effort. Nothing makes us realize that we're all part of one world than seeing the big blue marble from lunar orbit. Yeah, CGI is a marvelous thing, but it ain't real. But with shuttles due to be retired and NASA opting for unmanned Mars landings, how do you inspire young people at home to get the kind of rocket fever so many of my contemporaries had?

Cue Snoop Dogg and Buzz Aldrin:

P.S. I'm still processing my China trip and working my way through the essays my students wrote on Science in China, but there will be future posts on those topics. I just figured it was about time I got back to work here.

tripping the light fantastic

One of the best things about blogging is the stuff you stumble upon while researching something else. Take, for instance, my recent Google search on optical fiber sensors. It led me, rather improbably, to the official Website and blog of Jean-Michel Jarre, a French composer, performer and music producer who has sold some 80 million records worldwide, making him one of the most successful musicians I've never heard about. (Jen-Luc Piquant, on the other hand, has far more wide-ranging tastes and has been savoring the YouTube videos of Jarre's live performances for quite some time.) Why did Jarre's name come up? Well, while reading about optical fiber sensors, I stumbled upon a mention of the laser harp: an electronic musical instrument that uses numerous laser beams, blocked at various lengths, to produce audible sounds. Jarre is the most prominent musician to use this instrument in his music. (He also uses various other cutting-edge synthesizers and electronic instruments, including the theremin.)

Laser harps have been around since 1976, when the first working prototype was invented by Geoffrey Rose, who built it out of a matrix of 5x5 laser beams in an octagonal frame. The laser harp is usually connected to synthesizer or computer to produce audible notes. The instrument only needs a single laser, although some of the newer versions employ multiple lasers that can be individually controlled by pulsing on and off. In the single-laser version, the beam is split into an array of parallel beams, usually spreading outward like a fan. (See this YouTube video of Jarre in concert to get an idea of how it looks and sounds. There have been rumors that the instrument is fake, but Jarre has just as many defenders. Regardless, the visual impact is pretty impressive!) 

Whenever a beam is blocked, the change is detected by a photodiode connected to the electronics, and the computer activates the relevant note. (That's in the frameless version favored by Jarre. The framed laser harp usually has an array of photodiodes embedded in the upper part of the frame.) By matching the timing of the reflected beam, the computer can determine which beam is being blocked, and therefore which note needs to be played.

Not just any old laser can be used to build a laser harp. You need one with at least 20 mW of power just to produce visible beams, but to get the best results, a laser with 500 mW of power or more is best. This means there's a high risk of suffering skin or eye damage unless one takes precautions: Jarre for instance, wears gloves when "plucking" the "strings" of his laser harp, and other users have been known to don protective glasses. Artist Jen Lewin has been known to use laser harps in her art installations. most notably at at Lincoln Center in 2000 and Burning Man 2005. And for those interested in perhaps building their own photonic instrument,, there are several online resources available.

Why on earth was I Googling optical fiber sensors in the first place? You might ask. Well, sometime last year, I came across a group of scientists at the Ecole Polytechnique de Montreal in Quebec -- led by a professor there named Raman Kashyup --who've created a novel musical instrument based on optical fiber. They call it a "photocello." It's not something that seems to have captured much attention in the scientific community -- I wasn't able to find hardly any mention of the photocello on the Intertubes -- but I still find the concept charming. The photocello employs a vibrating optical fiber to reproduce vibrations that mimic those of a stringed acoustic musical instrument (like a normal cello, for instance). Rather than several different strings, the photocello just needs the one optical fiber, and one common detector (a photodiode).

Optical fiber sensors are used in lots of different applications these days: to measure strain, temperature, pressure, or other useful parameters. These sensors detect a change in one of the properties of the optical fiber, and then translate that detected change into a signal that can be "read" or otherwise used in some way. For instance, optical fiber sensors are used in hydrophones used in seismic or SONAR applications; they are also used to measure temperature and pressure in deep oil wells -- an environment that is not especially hospitable to standard semiconductor sensors. And the Boeing 767 uses an optical fiber as a sensor in its optical gyroscope.

The Montreal scientists exploited an intriguing feature of optical fiber: a single one can represent the "richness of the multitude of harmonic frequencies," which is why the photocello only needs a single optical fiber sensor instead of several different strings. The optical fiber "string" can produce many different notes depending on which section of the stretched fiber one chooses to focus on. Perturbing a stretched optical fiber -- by plucking it, or otherwise causing it to vibrate, in any given segment -- creates a change in the interference pattern, which can be detected by the photodiode and then, through computer processing, demodulated into a reproduction of the harmonic vibrations one would find a stringed musical instrument. The sound is barely audible, although it can be easily amplified to recreate specific musical notes.

Kashyup has also built a photonic guitar, replacing the nylon strings on the frame of a standard acoustic guitar with a multimode optical fiber. Hit one string, and it generates a wave, which can then be transformed into an electrical signal using a photosensor. As with the photocello, the signal can then be sent to a typical audio system with amplifiers and speakers to produce audible notes.

Kashyup is certainly a prolific inventor. Fresh on the heels of his photocello -- which was recently featured in a Quebecois business newspaper called Les Affaires -- he has developed a new scheme to increase substantially the output power of a fiber amplifier. Apparently, the amplification takes place in the doped fiber cladding, not in the core (which is how it's done in the usual method). More specific details weren't available (at least not easily), probably because there's a patent pending.

I still think the photocello concept is pretty cool, as is the photonic guitar. You can listen to a sample of Kashyup "playing" the latter instrument here. It's a bit rougher-sounding than an acoustic guitar, but who knows? Kashyup might be the harbinger of the future of musical instruments. Jean-Michel Jarre could be working the photocello into future live performances as I type -- it should complement the laser harp quite nicely.

i hear the cosmos singing

Things have been so hectic of late that I almost missed this February 28 article in Nature announcing that the new Kjell Henriksen Observatory on Svalbard, a remote Norwegian island, is now open for business. The observatory is described as "a window into space," since it's designed to study aurora borealis, a.k.a. the Northern Lights, and thus it is outfitted with highly sensitive optical instruments from some 16 institutions in seven different countries -- the better to perform those studies. The spectacular kaleidoscopic effects of the Northern Lights result from the collision of charged particles dumped into the Earth's magnetosphere by perturbations. The lights tend to only be visible in polar regions because those particles follow the Earth's magnetic field lines -- which fan out from the vicinity of the poles.

Hence, the location of the new observatory in such a frigid area. It's not exactly an ideal working environment for the scientists there: a polar winter is harsh, and pretty much from late October until, say, mid-March, Svalbard is stuck in almost 24-hour- darkness. And what a commute! They have to drive along an ice-bound Advent Valley to the island's only remaining functional coal mine, and then hop into army-surplus  vehicles outfitted with caterpillar threads to get them up to the top of Advent Valley. And they can't even use their headlights, since it will interfere with the sensitive instruments. The Nature article reports that at the moment, the scientists can't even get into the building via the main entrance, since it's currently buried under snow; they have to use the back door. If a storm hits, they resort to sleeping in bunk beds.

Finnish Lapland -- home to the Sodankyla Geophysical Observatory (SGO) -- is only slightly more hospitable. It, too, is a vast frozen expanse, and eerily silent much of the time because of the pronounced lack of foliage. The slightest of sounds can be amplified over large distances; in fact, I'm told that it's possible to hear dogs barking from villages a mile or so away. The indigenous Sami people tell stories of the aurora borealis singing and whistling as its light approaches earth. In the Sami language, "aurora" translates into "audible light." 

Audible Light

Needless to say, I'm a huge fan of this sort of natural phenomenon, but Irish-born artist Anna Hill has gone way beyond the admiring awe most of us feel at such displays. In March 2003, she trudged into the frigid landscape with her trusty Hassleblad camera and a video cameraman named Mark Szassy in tow. They were there not just to photograph the Northern Lights, but to make low frequency radio field recordings of the the swooshing and crackling sounds that locals believe are associated with the most intense auroral displays.

The result of all her hard work was "Aural Synapses," an award-winning multimedia art project that debuted at the Kilkenny Arts Festival later that same year. (You can hear a sound sample of these low-frequency sounds here, and a radio interview with Hill here.) It's not just the stunning visuals that made the exhibition such a success: it was also the haunting, eerie soundtrack that blended Hill's field recordings of the Northern Lights with the ethereal vocals of Irish singer/songwriter Iarla O'Lionaird and electronic instrumentals.

It's safe to say that the majority of scientists who do research in this field are skeptical of the notion that the aurora's dazzling light show has its own built-in soundtrack, but while visiting Lapland, Hill worked closely with a geophysicist who does: Esa Turunen of the SGO, whose research focuses in part on scientifically establishing the audibility of the phenomenon. Certainly the aurora borealis produces sounds in space, and those sounds are monitored and recorded regularly by observatories all over the globe, including the SGO. But the sounds heard on Earth are probably more local in origin.

Field instruments are finally sensitive enough to capture these weird sounds for empirical analysis, hampered a bit by the fact that the sounds only occur during the most intense geomagnetic activity. The Helsinki University of Technology (HUT) has an Auroral Acoustics program that statistically analyzes field recordings of auroral acoustics and compares them to a "control group" of recordings from nights when there was no geomagnetic activity. It's an ongoing project, but to date, findings support the anecdotal evidence: the sounds are real, they strongly correlate with particularly intense auroral displays, and they are produced locally, although scientists remain mystified by the exact mechanism doing the producing.

Not that Anna Hill needed convincing, having heard the sounds firsthand. "Aural Synapses" is her attempt to let others share her experience, using music, photographs and technology to make the installation as interactive as possible. For instance, the exhibit featured an interactive contact microphone, inspired by the breath sensors used by NASA astronauts: viewers could breath into it and the audio and visual elements would "react" to the breathing patterns. Right now, Hill is involved with a project called Space Synapse, in conjunction with the European Space Agency, developing a "Remote Suit": a wearable computer intended for remote communication of sensory input and telemetry from extreme environments, both on Earth and in space. The very first prototype? Why, the Auroral Suit, of course! It responds to data gathered from the ionosphere using wireless transmissions from Sudden Ionospheric Disturbance monitors. Anyone wearing the Auroral Suit can listen to the sounds of the Northern Lights. We would love one, but it's still in the prototype phase. Also? I'm guessing it will be crazy expensive.

Musical Plasmas

I know what all you movie fans are thinking right about now: "But I thought in space, no one could hear you scream?" Technically, the famous Aliens tagline got it right: sound needs a medium through which to propagate, and there isn't much of one in deep space, which is about as close to a cold, dark perfect vacuum as you can get. But there's some fine print. Poke around between the planets and other celestial bodies, and you'll find plasma (hot ionized gas), i.e., in the atmospheres of Venus, Mars, and Saturn's moon Titan, not to mention Ganymede, one of the moons of Jupiter. Plasma gas is thinner (by a lot) than the Earth's atmosphere, but it's just dense enough to allow sound waves to propagate. In fact, according to Don Gurnett, a physicist at the University of Iowa who builds plasma wave receivers for NASA, the sounds of space are far more varied and complex than on Earth, because of the ionization: plasmas produce a mixture of acoustic and electromagnetic waves (the latter usually in the radio frequency of the spectrum).

Gurnett says that when his team first launched a plasma wave receiver into Earth's orbit in 1962, they were "astonished to find that space is filled with a rich variety of sounds." He's been collecting recordings of space sounds ever since (more than 40 years now!), from all the major missions, including Voyager I, Galileo, and Cassini. What do plasma waves sound like? It depends. Lightning produces whistling sounds, regardless of whether it strikes on Earth or on Jupiter, and of course, so do the charged particles in Hill's aurora borealis. The magnetic fields surrounding the planets can trap electrons, producing bird-like chirps. And the sun emits high-velocity plasma known colloquially as the solar wind, which produces turbulent shock waves and an accompanying roaring boom.

To Gurnett's ears, it sounded a lot like music. Minimalist composer Terry Riley agreed when he heard them: he drew inspiration from Gurnett's recorded space sounds while composing "Sun Rings" for the Kronos Quartet several years ago. "Sun Rings" is a suite of 10 "spacescapes," each a complex layering of musical elements combining Gurnett's celestial sounds with projected space images and the world-famous string quartet in a live multimedia production. (Note that multimedia seems to be all the rage when it comes to making music from the sounds of space -- the marriage of visual and aural is an unbeatable combination!) Composing the piece took Riley over a year, and made for some interesting inspirations. He's said in interviews that the crackling and squealing sonic patterns from the magnetic field around Ganymede reminded him of a voice saying "beebopterismo" -- and that became the starting point for one of the movements in the "Sun Rings" suite.

"Sun Rings" first debuted in 2002, and has been performed all over the world since then, garnering rave reviews. For instance, the Los Angeles Times dubbed it "an empyrean masterpiece" that ushered in "a whole new chapter in the age-old quest for a music of the spheres." (You knew someone had to bring up that Pythagorean chestnut, right? If they hadn't, I certainly would have done so. Jen-Luc Piquant would never forgive such a lapse.) Alas, the Kronos Quartet has yet to make an official commercial recording of the suite -- they're very busy people, in high demand -- but it's only a matter of time. I hope. It could be an expensive proposition given the multimedia aspect. Why can't NOVA team up with Masterpiece Theater or that PBS staple, "Great Performances," to share the costs? Granted, Riley isn't the most mainstream of composers, but I don't see how you go wrong with Kronos + Pretty Pictures of Space + Weird Cosmic Sounds. While we're waiting, you can listen to some samples at Gurnett's Website and on NPR.

David Harrington, artistic director for Kronos Quartet, told the Tucson Weekly in 2002 that he considered Gurnett "an instrument maker.... He made an instrument that was able to translate plasma waves into sound. Gurnett is more circumspect, insisting that he's no musician, and doesn't even play an instrument. But he admits that he must have some innate musical sensibility: "I always recognized these sounds as having a musical quality. That's why I started collecting them in the first place."

As with the aurora borealis, the exact mechanisms by which these sounds are produced remain something of a mystery. "If you're sitting in an absolutely quiet room, you don't expect the molecules in one particular corner to the room to suddenly start singing at you, but this actually happens in a plasma," says Gurnett. And studying this unique acoustical feature of plasma does have some bearing on a far more practical concern: making controlled fusion a viable energy source here one earth. One of the biggest problems with generating nuclear fusion in our big terrestrial machines (like ITER, still under construction) is that the machine starts generating these plasma waves, thereby disturbing the orbits of the subatomic particles. The result is massive energy losses, which is one of the main reasons why we have yet to tap into the sun's energy source to meet our own growing energy demands. The conversion rates (and economies of scale) just aren't up to par yet.

Riley's suite, and Hill's multimedia installation, might challenge some people's concept of the kinds of sounds we consider to be "musical," i.e., aesthetically pleasing. But the underlying physical observations -- the sounds of the cosmos -- challenge our basic assumptions of what constitutes "sound." Most of us think of sounds as something we can hear, but in truth, our range of hearing is limited to a very narrow frequency range. In fact, we're talking about simple pressure waves traveling through a medium, at frequencies that are both too high and too low for the human ear to detect -- not just those waves whose frequencies we can hear directly. As such, acoustics provides a useful new lens through which to view celestial phenomena. That's why studying the acoustics of celestial bodies is pretty much all the rage these days in astrophysics circles. For instance, check out Paul Burke's sonification of a pulsar, or this analysis of ultrabass sounds of the giant star Xi Hya. Artists like Hill, and composers like Riley, are just taking that fundamental research and putting it to excellent aesthetic/creative use.

Paint It Black

My personal favorite acoustical object in the cosmos is "singing" black holes. NASA's Chandra X-Ray Observatory first detected sound waves from a super-massive black hole in the Perseus cluster in 2003 -- revealed via ripples in the gas filling the cluster. (I'd bet a nonfat latte that Phil Plait covered this when the news first broke.) Translated into musical terminology, the pitch of the sound is equivalent to the note of B flat -- albeit a B flat 57 octaves below middle C. A typical piano, if you care, only has about seven octaves. So we're talking about a frequency over "a million billion times deeper than the limits of human hearing." The press release claims it is "the deepest note ever detected from an object in the universe." (Jen-Luc opines that at least it isn't the infamous "brown note," which corresponds to F sharp, or 46.25 Hz.)

In this case, scientists think they understand the mechanism at work to produce the "sounds": the supermassive black hole's greedy, guzzling eating habits. Basically, objects that pass beyond the event horizon fall toward the center of the black hole, and as they do so, they produce a magnetized jet of high-energy particles powerful enough to blast away from the black hole close to the speed of light. (How this fits in with the notion that nothing can escape a black hole, not even light, is a bit puzzling to me, but we'll go with it for now. Feel free to offer clarifications!) That jet plows into the surrounding gas, creating a magnetized bubble of high-energy particles, and as often happens with a collision, this in turn creates a shock wave -- intense sound waves rush ahead of the expanding bubble. The rippling remnants of that shock wave are what Chandra detected.

A Primal Scream

Finally, how can we not mention Mark Whittle? Whittle is a humble astronomy professor at the University of Virginia who made headlines around the world in 2005 when he unveiled his simulated soundtrack to the birth of our universe 13.7 billion years ago. The Big Bang is a bit of a misnomer: technically, it was neither big, nor a bang, and Whittle's analysis reflects that. He describes the associated birthing cries as "a descending scream, building into a deep rasping roar and ending in a deafening hiss" -- which sounds an awful lot like the sounds made by mothers giving birth, to the terror of anyone in the delivery room with them at the time. As with mothers, so with our cosmos. In the first 380,000 years of the universe, it was filled with a "rapidly expanding, hot glowing fog" -- essentially a primordial cosmic atmosphere. So yes, there could be sound in the early universe.

The Cosmic Microwave Background Radiation, first detected in 1963 by Bell Labs scientists, is the "echo" of that first primal scream... a kind of "hiss" that permeates the universe uniformly. In 2003, the Wilkinson Microwave Anisotropy Probe (WMAP) generated its own headline when it provided the most detailed microwave map of space to date. It revealed minute variations  in the background radiation, and the peaks and troughs of sound waves traveling through the early universe. The sound spectrum spans about 10 octaves, all well out of the range of human hearing, and thanks to computing technology, Whittle was able to translate that into an audible version and condense that first 380,000 years into five seconds. Have a listen here. It sounds rather like a jet engine slowly turning into static or white noise.

See? There's an entire universe of sound out there, just beyond our ken, that most of us never stop to think about. Adjust our thinking just a tad bit more, and we can view the quantum world in an acoustical light (pun unintended, but a propos) as well. Since they phrase it better than I ever could in a mere blog post, I leave you with this prescient quotation from a 1988 book by Frank Wilczek and Betsy Divine, Longing for Harmonies: Themes and Variations from Modern Physics, in which the authors describe the spectrum of light at various wavelengths emitted from an object (an atom, for instance) as "its own unique chord":

"[the] marvelous dream [of the music of the spheres] is in fact closely realized in the physical world. The spheres, however, are not planets, but electrons and atomic nuclei, and the music they emit is not in sound but in light.... If our eyes were more perfect, we would see the atoms sing."

Thanks to the glories of modern science, we can not only see unprecedented images of our universe that would otherwise be beyond our limited sensory ken -- we can also hear (literally!) the age-old "music of the spheres."

makes me wanna yodel

When pop star Gwen Stefani took the stage at last December's Billboard Awards event to perform her new hit single, "Wind It Up," clad in a snazzy alpine-inspired outfit, it was done in tribute to that classic scene in the film The Sound of Music, in which the von Trapp children, led by Maria, perform a puppet show to "The Lonely Goatherd." C'mon, you all know the lyrics: "High on a hill lived a lonely goatherd..." Maybe it's the distinctive yodeling refrain, but I loved that tune as a kid, and found it impossible not to sing along, to the annoyance of anyone else who happened to be in the room at the time. (Jen-Luc Piquant does the same thing to West Side Story's "America," not that she'd ever admit to it.)

Apparently Stefani has a similar fondness for old musicals. Not only did she do a catchy hip-hop version of "If I Were a Rich Man" from Fiddler on the Roof, she samples "Lonely Goatherd" in "Wind It Up" -- that's right, the Hollaback Girl turns into the Yodelback Girl, at least for the duration of the song.  Another person who loves the goatherd song is Kerry Christensen, "one of the world's most versatile yodelers" -- and who am I to argue with Wikipedia? He performed for over an hour at the Acoustical Society of America meeting in Salt Lake City, demonstrating an impressive array of yodeling styles and techniques, interspersed with amusing anecdotes and fascinating historical trivia about yodeling.

Frankly, nobody sets out to become a professional yodeler, but Christensen took a shine to it as a hobby, and it turned into a career. He spent seven years performing at Walt Disney World's Epcot Center in Florida, which is also where he learned to play the chromatic accordion, alp horn and zither. But the Disney life became tedious: he did several shows a day, always the same tunes, with little chance to flex his creativity and explore what I was surprised to learn is a vast repertoire of yodeling music. And so he went solo.

Christensen actually lives in nearby Provo, but takes his yodeling act to folk festivals, state fairs, and similar events all over the world, "wherever it's appreciated." Utahans are not very appreciative, it seems: he only performs locally a couple of times a year. It reminds me of an old joke my cabaret singer/songwriter friend Peri used to make: "Q: What's the unlikeliest phrase in the English language? A: 'Is that the banjo player's Porsche?'" Like banjo players and Rodney Dangerfield, yodelers don't get no respect.

Who knows why that is? Because yodeling is a very old tradition that spans several different cultures. True, the word "yodeling" derives from the German jodeln, meaning "to utter the syllable jo." The type of yodeling most familiar to us can indeed be traced back to the German, Swiss and Austrian regions, where it was used as a communication system between alpine peaks, before finding international success in those old Swiss Miss instant cocoa commercials. Nonetheless, while "the Swiss think they invented yodeling," according to Christensen, he has traced its roots back to Africa.

Apparently Tibetan monks first used a form of yodeling to communicate. Marco Polo brought that knowledge back with him to Western Europe, where it quickly became part of the alpine tradition, eventually producing classic tunes like the first one Christensen performed, about a Swiss dairyman who swears if he yodels fast enough, he doesn't even have to milk the cows; they just spontaneously empty their udders. The American cowboy yodeling tradition -- yippee-kay-yay, y'all! -- came about because European immigrants brought the vocal style with them to the range. The cowboy yodeling patterns aren't as varied as the European traditions. They tend to be slower and simpler, since they were primarily lullabies to calm the cows at night, and also to soothe the animals during milking.

There's one thing you can say for yodeling: acoustically, it's pretty darned distinctive. Human voices have two distinct vocal registers: the head and the chest. Yodeling essentially involves singing an extended note that rapidly, and repeatedly, shifts in pitch between those two registers -- a skillful technique similar to those employed by professional opera singers, albeit for a very different final sound. Yodeling requires the singer to rapidly switch registers within a few seconds at high volume. Essentially, the voice momentarily breaks. Less practiced yodelers often lapse into falsetto, but skilled singers, like Christensen, can smoothly make the transition between registers without doing so.

Listening to Christensen's description and performance, I was reminded a little of Tuval throat-singing, sometimes referred to as overtone singing. They're not entirely un-related, although throat-singing focuses on reinforced harmonics rather than the rapid shifting vocal registers that characterize yodeling. In fact, a famed Texan singer of traditional cowboy songs in the 1920s called Arthur Miles was known for substituting overtone singing for the more customary yodeling in his recordings.

Anyway, "The Lonely Goatherd" is included in Christensen's extensive repertoire of some 1500 tunes, a list of which was distributed to the audience in advance so they could make specific requests.  I admit, despite being drawn by the quirkiness of the event, I deliberately sat in the back of the room for Christensen's performance, convinced that 30 minutes of yodeling was about all I could stand and I'd need to beat a hasty retreat. But Christensen was so entertaining and likeable, I stayed for almost the entire thing. Jen-Luc, being a faux-French snob, shuddered in horreur at the very thought and skipped the event altogether. Her loss: she missed out on Christensen's rousing yodel rendition of "The Lion Sleeps Tonight,"  which he claims originated in Africa, long before the Tokens made it famous.

Yeah, you heard me: I enjoyed the yodeling. Wanna make something of it? Do ya, punk? It's not like I plan to rush right out and learn how to yodel myself, although this handy online site promises to teach me in 10 easy lessons.

For a yodeler, Christensen's pretty darned inventive, and has an excellent grasp of the basic science behind his song stylings. That's why he can play around with it and come with a few new twists. Take the time he forgot the words mid-song and resorted to playing the "mouth trumpet": he developed that into a "Louis Armstrong Medley," and he sounds eerily like a trumpet when he performs it. A woman came up to him afterwards and congratulated him on his impressive mouth trumpet, then challenged, "But can you do that and yodel at the same time?" Christensen's initial reaction was no, he couldn't. The two styles require very different techniques. Yodeling must be loose and totally relaxed to get those smooth transitions between registers, while the mouth trumpet needs to be more pinched off, especially at the lips, which mimic the reed/mouthpiece of the actual instrument. Still, he went back home and practiced for over five hours, and finally managed to come up with a hybrid style he terms the "yodelumpet." He believes he is the only yodeler to sing this way, which is probably a mercy -- it's fascinating as a novelty trick, but one wouldn't exactly call it mellifluous.

Audience members seem to challenge Christensen a lot. A jazz musician once bet he wouldn't be able to perform a jazz version of yodeling, but Christensen promptly launched into a series of rapid, chromatic runs up and down the scale, yodeling the entire time, and the musician admitted defeat in less than a minute. He's come up with a cajun zydeco yodeling song, too.

The performance wasn't all about the yodeling. Christensen rested his voice a bit by playing a couple of tunes on the alp horn -- an impressive feat all its own, considering the acoustical properties of the instrument. The standard size is 13-1/2 feet long, the same length a French horn would be if you uncoiled it. (Interesting tidbit: For some reason, the Swiss insist on alp horns that play in F-sharp; it's handy for group performances, because if the horns aren't precisely tuned, you've got an acoustical mess.) Unlike conventional horns, which are made of brass, the alp horn is made of wood. This means there is much more air resistance to overcome, so playing the alp horn takes roughly three times as much air as a full-sized tuba. And Christensen was playing at the relatively high altitude (with associated thin air) of the Greater Salt lake region.

All in all, Christensen's performance supplied the perfect end to a long day of fascinating technical sessions. I can't wait for all the assembled acousticians in the audience to buy his CDs en masse and start analyzing the spectra in detail. Next year's spring ASA meeting could have more papers on the acoustics of yodeling than in the society's entire history. I might pick up a CD myself, if only to torture the cat.

silly science songs

Former Bell Labs physicist Jan Hendrik Schoen was a bit of a wunderkind back in 2001, hailed by some as a modern-day alchemist because he'd managed to get electricity to boldly conduct in certain materials (like pentacene) that had never conducted before. Barely five years out of grad school, the German-born Schoen's name was already being bandied about as a Nobel Prize contender.

It all went horribly, tragically wrong a year later, when physicists discovered that Schoen's most impressive experimental data had been fabricated. To put it bluntly, he made stuff up. It's not the kind of thing the physics community takes lightly, nor should it be. Author C.P. Snow (himself a scientist), in his novel The Search, said fraud was "the most serious crime a scientist can commit." A specially appointed panel of scientific experts agreed, declaring that Schoen had demonstrated "a reckless disregard for the sanctity of data in the value system of science." It is unquestionably among the darkest moments in recent physics history.

Consequences fell hard and fast once the deception was exposed. Schoen literally lost everything: his Bell Labs job, a prestigious appointment as director of one of the Max Planck Institutes in Germany, several prizes he'd been awarded, even his PhD. He returned to Germany in disgrace and quickly faded into obscurity.

Until now, that is. Schoen has been immortalized in a satirical musical composition called "Fabricate," sung to the tune of "Cabaret," and penned by physics professor Laura Greene of the University of Illinois. It contains the resounding chorus, "Come and just fabricate, young Schoen/ Come and just fabricate!" (You can find the complete lyrics here.) Can a Broadway musical be far behind?

Greene performed the tune in person Wednesday evening at a "physics singalong" event, part of the APS March Meeting in Baltimore. That's right, the normally sober and staid APS sponsored an entire evening of scientists stumbling over unfamiliar words to familiar tunes while being accompanied by a guitar and a bongo. (Richard Feynman would have been there in a heartbeat.) Some of the 50-odd folks in attendance even indulged in a little impromptu swing dancing. Those wacky, unpredictable physicists! What's next, cosmological karaoke?

An unsuspecting passerby might have been pardoned for concluding that the physicists had simply cracked from all the pressure of three full days spent juggling 15 different parallel technical sessions on everything from superfluidity and evolutionary dynamics to exotic nanostructures. But singing songs about physics is a long, time-honored tradition that originated -- where else? -- in England. At least that's what singalong organizer Walter Smith says, and I'm not one to argue the point. Smith is a physics professor at Haverford College who runs what he describes as the premiere online collection of physics songs in the world. (Jen-Luc Piquant somewhat snidely points out that it may very well be the only such collection. But she'd be wrong.)

I was fascinated to learn that the illustrious 19th century physicist James Clerk Maxwell -- author of the famous wave equations for light -- also composed alternate lyrics to the then-familiar folk song "Comin' Through the Rye," substituting the meeting of two young lovers with a rumination on the physics of collisions. By the early 20th century, Cambridge University's Cavendish Laboratory had made singalongs a tradition of their winter holiday parties, with participants like J.J. Thomson (who discovered the electron in 1897 and snagged a Nobel Prize for his trouble) standing on chairs and singing parodies at the top of their lungs. One assumes that copious pints of beer were involved, an element that was distinctly lacking at the APS event. That might have been a good thing. As my friend James Riordon (the guitarist for the evening) put it, "You really need to have your wits about you when you're trying to sing about electromagnetism."

Before he achieved national fame for his satirical ditties, Tom Lehrer was a physics grad student at Harvard, where he penned an entire musical show called The Physical Revue. In-joke alert: the title parodies a leading physics journal, The Physical Review. There's even an accompanying animation available online for Lehrer's classic "The Elements," whose lyrics are nothing more than a clever recitation of the periodic table. (I nicked -- or "gacked," if you will -- the link from Angela Gunn's TechSpace blog at USA Today. I was hugely flattered to find my own nascent blog mentioned there a couple of days ago. Fortunately, I have lots of good friends standing by, ready to puncture any spontaneous ego-inflation and nip self-importance in the bud. Jen-Luc Piquant, however, is demanding her own luxury Cyber-dressing room and a host of new designer outfits, claiming "her public" mustn't be disappointed.)

Physicists naturally revere Tom Lehrer, and are always on the lookout for an heir apparent. Smith himself penned most of the songs featured at Wednesday's singalong, including "The Love Song of the Electric Field" (sung to the tune of "Loch Lomond"). It's a rare individual who can make a song about an electric field and a magnetic field, united in an electromagnetic wave, almost, well, touching.

Taking a somewhat sassier approach is "Physics Chanteuse" Lynda Williams. She's been performing her "Cosmic Cabaret" all over the place for years, shimmying around the stage in a low-cut black cocktail dress while crooning "Carbon is a Girl's Best Friend" -- and inexplicably incurring the wrath of several female physicists who feel her act is "inappropriate" and demeaning to women scientists. The men, not surprisingly, have no such misgivings. I've never understood the objections myself -- what, a woman scientist can't be funny and sexy, as well as smart? (Note to self: file away for a future rant.)

My own forays into science singalongs have been few and far between. Quite often, a surplus of margaritas are behind the lapse in judgment, although who can resist the timeless appeal of Monty Python's "Galaxy Song," or They Might Be Giants crooning, "The sun is a mass of incandescent gas..." -- not to mention the entire "Schoolhouse Rock" oeuvre? Still, you're far more likely to catch me bumping and grinding  (and sometimes air-guitaring) in front of the bathroom mirror to the dulcet tones of The Dandy Warhols or The Tragically Hip, while my cat stares balefully from her perch du jour.

I think the silly-physics-song tradition is kind of sweet. Wednesday's singalong provided a much-needed breather to the nonstop onslaught of technical data, which can lead to the dreaded "March meeting hangover" in the uninitiated, or faint of heart. Physicists may be a bit tedious at times when it comes to the minutiae of their research, but from a big-picture standpoint, they're pursuing the most elusive secrets of our universe. If Wednesday night's festivities are any indication, they're doing it with a silly physics song in their hearts.