Question

The power of sound from the speaker of a radio is 20 mW. by turning the knob of volume control the power of sound is increased to 400 mW. if the sound is detected from a fixed distance from the speaker, find the increase in intensity

• A. 1.3 dB
• B. 3.1 dB
• C. 13 dB
• D. 30.1 dB

Answer 1

Answer: (C)

13 dB

Given data: Initial power= $20mW$

Final power = $400mW$

The increase in the loudness level or intensity is given by:

$\Delta L=10log\frac{P_2}{P_1}=10log\frac{400}{20}=10log20=13.01dB$