Monday, October 31, 2011

Cell Phones: Why You Can't Hear Me Now

Cell phones cut off the highest-pitched ranges of our voices, making it hard for others to hear us. Corbis


-Our voices transmit information at frequencies much higher than scientists have long thought they could.

-Cell phones cut off the high-frequency sounds in our voices.

Discovery News - On a bus or in a bar, cell phone conversations can lead to major frustration. But it’s not just volume or poor reception that makes it so hard to hear the person on the other end of the line, according to a new study.

Cell phones also cut off the highest-pitched ranges of our voices. Those high-frequency sounds convey a surprising amount of information, according to the study.

NEWS: Your Brain Hears Silence

The results suggest that we may be missing the full meaning of what people say when we talk to them on our mobile devices.

“The prevailing thought was that, because high frequencies are not as loud in the voice, that the brain must not pay much attention to them,” said Brian Monson, a speech and hearing scientist at the University of Utah, Salt Lake City. “If the brain is paying that much attention to high frequencies, there must be some kind of perceptual information there.”

A typical male voice measures about 100 hertz and an average woman speaks at about 200 Hz. Unlike a monotonic sound like a whistle, voices also contain quieter overtones with frequencies that range as high as 20,000 Hz. But because most of the energy in our voices falls below 5,000 Hz, scientists have long assumed that those high-pitched sounds are irrelevant.

Monson, who is also a singer with experience as a sound engineer, started to suspect that assumption a few years ago. While working with other singers, he noticed that they improved the quality of their voices by making adjustments in very high frequency overtones. In a follow-up project, he found that people could detect tiny differences in the volume of high-frequency sounds – on the scale of just a few decibels.

For the new study, Monson recorded people speaking and singing the Star-Spangled Banner. He filtered the recordings to keep only sounds above 5,000 Hz. He played those recordings to about 50 people in a handful of experiments. Then, he asked listeners to try to identify details about what they heard.               More