• Sound absorbing coefficient is defined as the inverse of the area of the sound absorbing material which absorbs an equivalent of sound energy as that of 1m2 of an open window.
• Coefficient of absorption usually lies between 0 and 1.
• It is a relative measurement where an open window is used as reference, since it transmits entire sound energy falling on it and nothing is reflected.
• In a hall, there are many other sound absorbing materials which play an important role in controlling the sound energy. To find the sound absorbing coefficient we need to take in to account the walls, the suspended objects like curtains, chairs, tables and also the audience.
• The acoustics of the hall should be designed such that the presence of audience shouldn’t matter much to the coefficient of absorption.
• The coefficient of absorption is measured in Sabine.

Solution:

Initial intensity= I

Final intensity= K

Ratio of Initial intensity to final intensity ie, I:K=1000

Increase in intensity level:

$X=10\ log_{10}⁡\dfrac{I}{K}$dB

$X=10\ log_{10}⁡1000 =10\times3$

$\therefore\ X=30$

Increase in intensity level = 30dB