Question

2. A noise source is placed in the centre of a semi-anechoic chamber. The sound level is 86 dB at 2m. Find the sound intensity and sound level at 2.5 m

Answer 1

At R = 2m, B = 86 dB = > 10 log I/10^-12 = 86 = > log I/10^-12 = 8.6 = > log I/10^-12 = 10^8.6 = > I = 3.98 times 10^-4 w/m^2 therefore P = I times 4 pi R^2 = (3.98 times 10^-4) (4 pi times 2^2) = 0.0200 w At R = 2.5 m, I = P/4 pi R^2 = 0.0200/4 pi (2.5)^2 = (2.55 times 10^-4)w therefore B = 10 log(2.55 times 10^-4/10^-12) = 84 dB