Physics 51b

(1) An example I did not have time to work out:

A giant chorus of 1000 male vocalists is singing the same note. Suddenly, 999 vocalists stop, leaving one soloist. By how many decibels does the sound level decrease?

Assume that all the vocalists sing at roughly the same intensity

Let the intensity of 1000 vocalists be Ia (and Ba expressed in decibel) and the intensity of 1 vocalist by Ic (and Bc expressed in decibel)

Ba=10log(Ia/Io) where Io is the hearing threshold

Bc=10(logIc/Io)

Ba-Bc=10log(Ia/Io)-10log(Ic/Io)=10log(Ia/Ic) =10log(1000/1)=30dB

(2) Please try the question on Doppler shift in the handout before class Wed!