Calculating Sound Room Absorption

To determine the absorptive/reflective ability of a sound booth:

wavelength = c (speed of sound) / f (frequency)

C = 343 m/sec or roughly 1000 feet/sec

for example :

A single walled sound booth is normally 3 inches in thickness.  To calculate the lowest frequency that this room can attenuate, we do the following.

[1000 feet/sec] / [1000 Hz] = 1 foot (or 12 inches)

12 inches  / 4 = 3 inches 

(we use 1/4 wavelength because it is a constant for acoustical measurement). 

This means that any wavelength over 1000 Hz will be absorbed by a single-walled sound booth.  

Double-walled sound booth are 12 inches.  The added thickness allows it to absorb more of the lower frequency sine waves.  Very thick walls are required to absorb low frequencies.  

For example, in order to absorb a 100 Hz signal, we need a wall which is 2.5 feet thick.  

i.e.  [1000 feet/sec] / 100 Hz = 10 feet

       10 feet / 4 = 2.5 feet

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