# Sound Intensities

1. Apr 25, 2006

### Huskies213

Does anyone know how to solve this ?

A group of people were exposed to 114 dB music for 60 minutes. Eleven of the 20 subjects showed a 17 dB reduction in hearing sensitivity at 4000 Hz. What is the intensity corresponding to the threshold of hearing for these people ? ( in W/m^2)

thanks

2. Apr 26, 2006

### Andrew Mason

The following information appears to be irrelevant:
"A group of people were exposed to 114 dB music for 60 minutes."
"Eleven of the 20 subjects"

We also do not know what their original hearing sensitivity at 4000 Hz was. People's hearing sensitivity varies. Are we supposed to guess?

Please check the question and provide all the information.

AM

3. Apr 26, 2006

### Huskies213

Re

Threshold = 10^-12 ...thanks for the help!

4. Apr 26, 2006

### nrqed

Normally, the threshold of hearing is at 0dB (so I= 10^-12 W/m^2). I assume that " a 17 dB reduction of hearing sensitivity" means that now their threshold of hearing is at 17dB. It is straightforward to calculate the intensity this corresponds to ($\beta = 10 log({I \over 10^{-12} W/m^2})$...the sound level is 17dB so you can solve for I). So if a sound wave has an intensity below the value calculated, they won't perceive the sound.

Patrick