# Two speakers

1. Apr 7, 2008

### amatol

1. The problem statement, all variables and given/known data
https://tycho-s.phys.washington.edu/cgi/courses/shell/common/showme.pl?courses/phys123/spring08/homework/01b/twospeaker_INT/02.05.gif [Broken]
(if image doesn't show up...it is a right angle triangle with S1 at the right angle, 4m between it and O and 3m between S1 and S2)

The two speakers at S1 and S2 are adjusted so that the observer at O hears an intensity of 4 W/m2 when either S1 or S2 is sounded alone. They are driven in phase (at the speakers) with various frequencies of sound. Assume that the speed of sound is 325 m/s.

a) Find the three lowest frequencies, f1 < f2 < f3, for which the observer at O will hear an intensity of 16 W/m2 when both speakers are on.

b) Find the three lowest frequencies, f1 < f2 < f3 , for which the observer at O will hear no sound when both speakers are on.

c) Find the lowest frequency for which the observer at O will hear an intensity of 8 W/m2 when both speakers are on.

d) Find the lowest frequency for which the observer at O will hear an intensity of 4 W/m2 when both speakers are on.

2. Relevant equations
I think these...
f=v/$$\lambda$$
Intensity= energy/tA
I also need to figure out the phase difference but not sure what formula

3. The attempt at a solution
so far I know that I need to find the path length difference between the two speakers to the observer...which is 1m. From that I need to find the phase difference which will give me the intensity. How to do this I am clueless on. Then I need to find the wave length from the difference between the two and from that I can find the frequency. (at least this is what I am thinking...but its not working! and I can't figure out the phase difference)

Any help appreciated!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: May 3, 2017