Question

In the absence of teacher a class of $50$ student makes a noise level of 50 dB. 50 more student enters the class. Assuming each student on an average produces the same intensity of sound than the noise level increases by

• A. $50dB$
• B. $25dB$
• C. $8.33dB$
• D. $3dB$

Answer 1

Answer: (D)

$3dB$

Let initial intensity be I then $10log\frac{I}{I_0}=50$ on arrival of 50 more students, new intensity = 2I
$=10log\frac{2I}{I_0}$
$=10log\frac{I}{I_0}+10log2$

$=50+10\left(0.3010\right)=53dB$

$\Delta S_L=53-50=3dB$.