Date:10/18/2011

dy designed to pinpoint the source of this and similarly irritating sounds, scientists found that the most obnoxious elements of the noises may be amplified by the shape of the human ear. In the study, scientists removed information from audio clips of people scraping their nails or bits of chalk against a chalkboard and played these modified clips to willing participants. The human ear is known to be particularly sensitive to pitches in the mid- to low-level range of frequencies, between 2000 Hertz and 4000 Hertz, which is the peak of human hearing. It turns out that when scientists removed all the pitch information in this range from the audio recordings, the study participants rated the noises as more pleasant than other versions of the sounds. So chalkboard squeak may be irksome because the most obnoxious elements of the sound sit right in the sweet spot of human hearing. Talk 4pPP6, "Psychoacoustics of chalkboard squeaking," is in the afternoon session on Thursday, Nov. 3.

Abstract: http://asa.aip.org/web2/asa/abstracts/search.oct11/asa888.html

Physicists shoot 'gunshot forensics' forward into science: The characteristic crack and bang of a gunshot blast may contain vital clues about a crime: who shot first, or even what type of firearm did the deed. But dozens of factors, from the angle and direction of the gun's muzzle to the quality of the microphone, can change the way a gunshot sounds in a recording, making it difficult even for expert analysts to tell exactly what went down at the scene of the crime. Now researchers from BAE Systems in Austin, Texas, and the FBI Forensic Audio and Video Analysis Unit have taken a major step toward improving scientists' understanding of how the sound of gunshots corresponds to the manner in which the bullets were fired. "The field of forensic gunshot analysis is relatively new," said Steven Beck, principal scientist for BAE Systems. "
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Contact: Charles E. Blue cblue@aip.org 301-209-3091 American Institute of Physics Source:Eurekalert

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