Newswise — For the ears, a cocktail party presents a chaotic scene: glasses clink, voices buzz, light piano music may waft down from the stage. A group of researchers at The John Hopkins University in Baltimore, Md., is trying to understand how the brain makes sense of such complex auditory environments. The team is testing how humans track sound patterns over time, and under what circumstances the brain registers that the pattern has been broken. The researchers will present preliminary findings at the Acoustics 2012 meeting in Hong Kong, May 13-18, a joint meeting of the Acoustical Society of America (ASA), Acoustical Society of China, Western Pacific Acoustics Conference, and the Hong Kong Institute of Acoustics.

“When a person hears a sound, both what we call ‘bottom-up’ and ‘top-down’ processes occur in the brain,” says Mounya Elhilali, an assistant professor at the Center for Language and Speech Processing at John Hopkins. Hearing a whole range of sounds in a room is a bottom-up process, but choosing to pay attention to a particular voice would be an example of a top-down process, Elhilali explains. “We try to understand the interaction of these two processes,” she says.

Elhilali and her colleagues ask volunteers to listen to a series of sounds and press a button when they hear something unusual. For example, the researchers may start out playing violin music and then introduce the sound of a piano. The change to piano music represents a change in the timbre, or sound quality. The researchers also changed the pitch (going from low to high notes or vice versa), and the loudness. As expected, results indicate that humans will perceive these changes as salient sound events that grab their attention.

Forming an expectation about the timbre, pitch, and loudness of sounds, and then realizing that the expectation has been broken generally takes a few seconds, says Elhilali, although the scientists are still in the process of fully analyzing their data. With further analysis the researchers also hope to glean information about how the different expectations interact and what happens when multiple changes, for example loudness and pitch, are made at the same time.

Eventually the team would like to repeat the experiments while monitoring the volunteers’ brain waves through sensors placed on the skin. This would offer the scientists a glimpse at the neural changes that take place in the brain as the sound scene changes.

The ultimate aim is to understand how the brain adapts to different acoustic environments, says Elhilali. Engineers might be able to use the knowledge to design better hearing aids, voice recognition software, and recording equipment. Elhilali’s group, which is based out of the Electrical and Computer Engineering Department, also works on such technological applications of the research. “When a person walks into a room, they first gather information that will help them adjust to the acoustic scene,” says Elhilali. One day hearing aids and other human-designed sound processing technologies may be just as adaptive as the human brain.


The 163rd Meeting of the Acoustical Society of America (ASA) will feature more than 1,300 presentations on the science of sound and its impact on physics, engineering, and medicine. This international acoustics meeting will be held jointly with the 8th Meeting of the Acoustical Society of China and the 11th Western Pacific Acoustics Conference. It is organized by the Hong Kong Institute of Acoustics and will take place May 13-18, 2012, at the Hong Kong Convention and Exhibition Centre. USEFUL LINKS:Main meeting website: Searchable index: Hotel site:

WORLD WIDE PRESS ROOMASA's World Wide Press Room ( contains dozens of newsworthy stories and lay-language papers, which are 300-1200 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio, and video.


This news release was prepared for the Acoustical Society of America (ASA) by the American Institute of Physics (AIP).

The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world's leading journal on acoustics), Acoustics Today magazine, ECHOES newsletter, books, and standards on acoustics. The society also holds two major scientific meetings each year. For more information about ASA, visit our website at

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Acoustics 2012 Hong Kong