The sound level at a point 5.0 m away from a point source is 40dB. What will be the level at a point 50m away from the source?
Physics · Wave Motion
JEE Mains Advanced

Question

The sound level at a point 5.0 m away from a point source is 40dB. What will be the level at a point 50m away from the source?

G1 Physics · Accepted Answer

Step 1: Intensity of a point source varies as 1/r². Increasing distance from 5 m to 50 m reduces intensity by 100. Step 2: Sound level falls by 10log₁₀(100)=20 dB. Therefore 40 dB becomes 20 dB.