Question
the ratio of intensities between two coherent sound sources is 4:1. the difference of loudness in decibel between maximum and minimum intensities, when they interfere in space is
(1) 10 log2
(2) 20 log3
(3) 10 log3
(4) 20 log2
Joshi sir comment
I1/I2 = 4/1 so a1/a2 = 2/1 so amax/ amin = 2+1/2-1 = 3/1 so Imax/ Imin= 9/1
now loudness L = 10 log(I/I0)
so difference of loudness = L1-L2 = 10 log (9I/I) = 10 log9 = 20 log3