1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Sound waves interference

  1. Mar 20, 2005 #1
    Here is a problem i do not know how to set up:

    Two speakers, driven by the same oscillator (f=200Hz). They are located on a vertical pole 4m from each other. A man walks straight toward the lower speaker, perpendicular to the pole. How many times will he hear a minimum in sound intensity and how far away from the pole is he at these moments? (take speed of sound to be 330m/s).

    Any help is appreciated especially equations to use and how to start this.
  2. jcsd
  3. Mar 20, 2005 #2
    Very nice problem thenewbosco. You must begin with the equations of the oscillations received by the observer:

    [tex] y_1=A sin(\omega t-kx)[/tex]
    [tex] y_1=A sin(\omega t-k \sqrt(x^2+h^2))[/tex]

    (x is the distance from the pole to the observer and h the pole's height and [tex]k=\frac{2 \pi}{\lambda}[/tex])

    In a first approximation (observer far away from the sources) we'll simply add these oscillations:

    [tex]y=y_1+y_2=...=2Acos\frac{2 \pi}{\lambda}(x-\sqrt(x^2+h^2))\cdot sin(\omega t+.......)[/tex]

    The amplitude of the resultant oscillation is given by the first part :
    and we must find x that gives you cos(....)=0 (interf. min.)
    Last edited: Mar 20, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook