Page 48 - Fall 2005

Acoustics in the News
􏰀 The songs of birds can have warning calls coded into them, according to a story in the 28 June issue of The New York Times that also appeared in the 24 June issue of Science. Consider the black-capped chickadee. By varying the call, a bird communi- cates to other birds the size of the predator, and thus the scope of the danger. They vary the number of “dee” sounds at the end of the call depending on the size of the predator. The more “dees” the more chickadees show up to harass the predator, by dive-bombing it or making noises in its face.
􏰀 Musical hallucinations can occur when neurons go awry, a story in the July 12 issue of The New York Times. Researchers have found that in two thirds of the cases studied, musical hal- lucinations were the only mental disturbance experienced by the patients. A third were deaf or hard of hearing. Women tended to suffer musical hallucinations more often than men. People tend to hear songs they have heard repeatedly or that are emo- tionally significant to them. Plans are being made to use MRI in order to catch second-by-second changes in brain activity.
􏰀 The male club-winged manakin, a tiny red-headed bird, lit- erally sings with its wings, according to a story in the August 2 issue of The New York Times. In an effort to attract the atten- tion of females, the bird rakes its feathers back and forth over one another, using an acoustic trick that also allows crickets to
sing. While the technique is common among insects, it has never been documented before in vertebrates. When the bird raises its wings over its back, it shakes them back and forth over 100 times a second. The frequency of the sound by raking the feathers, however, is around 1400 Hz. The sound is report- ed to be loud and clear, not unlike the sound of a violin.
􏰀 Technological wizardry will transform the changing shapes of clouds into live music, according to a story in 22 July issue of Science. The new instrument, called a “Nomadic Cloud Harp,” will translate the shapes of clouds into sound as they pass over. The cloud harp will use a laser to read cloud surfaces and a computer program to convert the shapes into an acoustic wave. “The sound is modulated by the height and density of the clouds,” says its creator.
􏰀 Computer analyses of audio recordings made in the woods of Arkansas have convinced ornithologists that the ivory-billed woodpecker is not extinct after all, according to a story in the August 2 issue of the Chicago Tribune. Using audio equip- ment set out in various places near the Cache and White Rivers last winter, Cornell University ornithologists made 17,000 hours of recordings. Some sounds, which included the bird’s distinctive double raps on a tree, were explainable only as being an ivory-billed woodpecker, they concluded.
46 Acoustics Today, October 2005