Problems form the Handout Spherical sound waves are emitted

Problems form the Handout * Spherical sound waves are emitted uniformly in all directions from a point source, the radiated power P being 25 W. What are the intensity and the sound level of the sound wave a distance r = 2.5 m form the source

Solution

Surface area of sphere is

S=4pi*r² =4pi*2.5²

S=78.54 m²

Intensity of sound wave

I=P/A =25/78.54

I=0.3183 W/m²

Sound Level in dB is given by

B=10Log(I/I_o)

where I_o=Lowest audiabe intensity= 10^-12W/m²

B=10Log(0.3183/10^-12)

B=115.02 dB