Page 51 - Spring 2006

Acoustics in the news
of Homeland Security as well as an appearance on TV. She designed a system that uses ultrasonic waves to detect broken train tracks to warn of impending collisions.
􏰀 Heavy use of IPods and MP3 music players may contribute to hearing damage, according to a story in the January 10 issue of The Wall Street Journal. Some doctors see younger and younger patients with signs of noise-induced hearing loss that wouldn’t typically emerge before middle age. Portable music players, which blare music directly into the ears, may be partly to blame. Hearing specialists at centers such as the House Ear Institute in Los Angeles, the Children’s Hospital, Boston, and the American Academy of Audiology say the effect they are seeing may be only the beginning, because accumulated noise damage can take years before it causes noticeable problems. Several companies now market headsets that aim to black out background noise so that the music can be heard better at lower volumes.
􏰀 Electronic stethoscopes, which make it easier to separate heart and lung sounds from a background of noise, make up only about 10% of the global stethoscope market, according to a story in the January 19 issue of The Wall Street Journal. Some electronic stethoscopes gather ambient noise through a thin slit around the chest piece and use it to cancel noise con- ducted through a patient’s body. Another improvement is the development of special ear tips that make a tighter seal in the doctor’s ear canal. Noise-reducing electronic stethoscopes are now seeing increasing use.
􏰀 “How to Listen for the Sound of Plutonium” is the intrigu- ing headline of an article in the January 31 issue of The New York Times which reports on a secret meeting of the science and technology directorate of the Central Intelligence Agency. The meeting brought together hundreds of the gov- ernment’s top experts in nuclear intelligence to address a problem that had bedeviled Washington for decades: how to know, with precision, when a country is about to cross the line and gain the ability to build an atomic bomb. Research has focused on better detection of “four basic, but inconspic- uous, signatures that covert nuclear facilities and materials can emit: distinctive chemicals, sounds, electromagnetic waves and isotopes, or forms of the same element that have different numbers of neutrons, a subatomic building block.” Details about the sounds, and how to detect them, are not given, but it is interesting that the headline writer picked up on an acoustical subject.
􏰀 A lawsuit has been filed in San Jose federal court ask- ing to limit iPod sound output to 100 dB, according to a story in the February 2 issue of the San Jose Mercury News. The suit notes that in 2002 France required Apple to limit the iPod’s sound output to 100 dB, but that the iPod sold in the United States is capable of producing music with sound levels between 115 and 130 dB. The user’s manual includes a warning that “permanent hear- ing loss may occur if earphones or headphones are used at high volume,” the suit acknowledges, but it does not advise listeners what is a safe volume.
􏰀 An expert on noise and hearing loss at Wichita State University has found sound levels as high as 120 dB in per- sonal music players, according to a story in the January 30 issue of the San Jose Mercury News. With ear buds there’s no escape from the intensity. Dangerous Decibels, an Oregon public health project, estimates that of the roughly 40 million Americans with hearing loss, 10 million cases can be attrib- uted to noise-induced hearing loss.
􏰀 “Risks Fall, Hopes Rise for Hearing Implants” is the comforting headline of a story in the March 7 issue of The New York Times. Earlier a high incidence of meningitis was found in deaf children with cochlear implants, but this was mainly in children with an implant type that is no longer on the market. Deaf children already stand a higher than normal chance of contracting meningitis, an infection of the fluid surrounding the brain and spinal cord, because they often have abnormalities in their inner ears. On the other hand, early implantation is important. Kids who are implanted by age 3 or 4 have language that is pretty normal and can be educated in mainstream classes rather than in special schools for the deaf. In the past 20 years, it is estimated that 11,000 American chil- dren have received implants. Early implantation is encouraged so that children can hear in the crucial years to learn language.
􏰀 In an attempt to give the public audible evidence of what is normally invisible, artist Carrie Bodle created a multi-speaker sound installation on the Green Building at MIT, according to a story in the September 12 issue of The Boston Globe. The speakers broadcast audio repre- sentations of sound waves embedded in the Earth’s upper atmosphere each day from noon to 1:00 p.m. for a week in September. In another story about the “Sonification/Listening Up” installation, the September 16 issue of the MIT newspaper The Tech reported that some listeners likened the experience to an airplane cir- cling overhead while others described it as a “big didgeridoo.”
􏰀 The debate over whether the Navy’s use of sonar to detect submarines is harming whales and other sound-sensitive species is back again, according to an editorial in the March 7 issue of The New York Times. This time the battleground is the waters off the southeastern states where the Navy hopes to establish a training area for sailors to practice their sonar skills in a shallow ocean environment. The National Oceanic and Atmospheric Administration (NOAA) has expressed significant concerns about the proposed sonar activity, including its potential to injure or kill beaked whales, which are especially sensitive. The agency also con- tends that the sound thresholds the Navy deems acceptable are well above the levels known to disrupt marine mammal behavior in the wild. While no one can deny that the Navy needs to conduct sonar training in shallow waters, the edi- torialist writes, it behooves the Navy to move with extreme caution.
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