posted by Sandhya on .
1) Sound propagating through air at 30 degree Celsius passes through a vertical cold front into air that is 40 degree Celsius. If the sound has a frequency of 2400 Hz, by what percentage does its wavelength change in crossing the boundary?
(2) What is the intensity of a sound that has intensity level of (a) 50 dB or (b) 90 dB?
(1) The sound speed increases in proportion to the square root of the absolute temperature change, sqrt (313/303) = 1.016. That is a 1.6% increase in sound speed and will result in a 1.6% increase in wavelength, since
wavelength = (sound speed)/(frequency)
2. Use the table at http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/sound/u11l2b.html
to find your answer
Thanks for your easy solution for prob1
By the way is it not 1.016% ?
I solved prob 2 using the formula
Intensity level L = 10 log(I / I0) where I0 = 10^-12 watt/sq.m