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Sound distance calculation

  1. Jul 31, 2012 #1
    I have two different sound sources (suppose two different person's voice playing in different volume).
    How to find which sound coming from further distance. What is the exact equation to calculate distance.
     
  2. jcsd
  3. Jul 31, 2012 #2

    Ibix

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    Science Advisor

    I'm not sure that there is one. What have you got to work with? What degree of precision do you want?

    If you've got three microphones you could use something like interferometry to figure out the bearing of the source from each pair of microphones and then do triangulation to get the distance. Precision drops off badly with range with this method.

    If you know something about the frequency spectrum of the sources you might be able to use dispersion to estimate the distance. Under some circumstances, waves of different frequencies travel at different speeds, so the spectrum will evolve with distance. I doubt you could place anything more precisely than a couple of hundred meters with this, even if it is possible.
     
  4. Jul 31, 2012 #3

    Bobbywhy

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    Gold Member

    anup08, Welcome to Physics Forums!

    The received (detected) sound pressure level (SPL) in dB without the given distance to the sound source is really useless for finding the range. Other than a complicated triangulation system, as proposed by Ibix above, there is one way you could measure the distance to those sources: If you knew the exact SPL at the source, and then measure the SPL at the receiving location, the distance to the source could be calculated by comparing the two levels.
    For the technical details, see:
    http://www.sengpielaudio.com/calculator-distance.htm

    Distance measuring devices typically transmit a short burst of sound toward a target, which reflects the sound back to the sensor. The system then measures the time for the echo to return to the sensor and computes the distance to the target using the speed of sound in the medium.
    A typical sound velocity in air is:
    T25 is 298.15 K (= 25 °C = 77 °F), giving a value of 346.1 m•s−1 (= 1135.6 ft/s = 1246 km•h−1 = 774.3 mph = 672.8 knots).
    http://en.wikipedia.org/wiki/Speed_of_sound
     
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