(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Two loudspeakers are set up 4.0 meters apart and are driven in phase by the same amplifier. The listener is located a sufficient distance away so the angle to the listener is approximately the same at each speaker as indicated in the drawing. The speed of sound is 344 m/s. What frequency would the speakers need to emit if the first intensity maximum from the central maximum occurs at an angle of 30° from the perpendicular to each speaker?

http://omploader.org/vMTBsaw/phys_diagram1.png [Broken]

2. Relevant equations

[tex]v=\lambda \cdot f[/tex]

There is also [tex]A = 2 A_0 cos(\frac{\phi}{2})[/tex] in the solution to the problem but I don't understand where this equation even came from. It's not in my book or anything.

3. The attempt at a solution

Well, I know I'm looking for f, the frequency. So I did [tex]f = \frac{v_{\mbox{sound}}}{\lambda}[/tex] but that's about it. Now the actual solution uses [tex]A=2A_0 cos(\frac{\phi}{2})[/tex] and [tex]\phi = k \Delta x[/tex]. I would like to understand where these equations came from. Are they universal for this type of problem, or were they somehow derived from the given information?

http://omploader.org/vMTBsbQ/phys_diagram2.png [Broken]

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Frequency of first intensity maximum for loudspeakers

**Physics Forums | Science Articles, Homework Help, Discussion**