Penn State acoustical engineers have used functional MRI scans, which measure brain activity by sensing changes in blood flow in the brain, to better understand our emotional response to sound reverberation and room acoustics.
According to Penn State researchers, noisy gymnasiums and restaurants where conversations are nearly impossible, and concert halls that are less than perfect for music, are all acoustical problems. The research team is looking at the emotional response to problems we experience with reverberation in room acoustics.
“Traditional methods of evaluating room acoustics use subjective rating methods, and part of our study uses this method,” said Michelle Vigeant, PhD, assistant professor of acoustics and architectural engineering. “The other part uses fMRI to see how changes in acoustics appear in the brain.”
In an article published in the October 2015 edition of the Journal of the Acoustical Society of America, Vigeant and co-author Martin S. Lawless, a PhD student in acoustics, explain that reverberation is a measure of how long a sound persists in a space after it is made. In concert halls, reverberation is used to support the music, but in many spaces the reverberation is excessive. For example, noisy rooms where background sounds seem to hang in the air making it difficult to hear speech or music have a lot of reverberance.
The researchers note that in regard to room acoustics there are many attributes that aren’t well defined, but for reverberation, most experts agree on what is considered a good range.
To test the emotional response to reverberation, the researchers used short pieces of music recorded in anechoic chambers — rooms that absorb all reflection and echoes of sound. These musical snippets were then altered to contain differing amounts of reverberation. The researchers report that they used musicians as their study subjects because musicians are accustomed to doing critical listening, and would therefore learn the testing activities more quickly than non-musicians, so their answers were likely to be more reliable.
Every person enjoys music selectively, the researchers reported. When something is pleasurable, certain areas of the brain increase activity, which shows up on the fMRI.
Vigeant and Lawless tested five subjects each in both an fMRI simulator and a real machine, scanning about 70 images in each machine, while at the same time asking the subjects to rate the music recordings on a scale from -2 to +2 as unpleasant to pleasant. Although the number of subjects in the study was small, each individual underwent 7 fMRI scans for each of the musical snippets with reverberation. The researchers found two subjects whose brains lit up in an area that signifies anticipation of pleasure when listening to certain music segments that they found pleasurable.
Source: Penn State
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