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Homework Help: Hearing Threshold Problem

  1. Apr 24, 2013 #1
    The sound level from a siren emitting sound with a frequency of 2400 Hz is 75.0 dB at a distance of 47.0 m from the siren. Assume that the intensity of that sound obeys the inverse square law. Calculate how far from the siren a person, with a threshold of hearing of 36.0 dB at that frequency, can be located to barely be able to hear the sound from that siren.

    I= P/4πr^2
    decibels(dB)= 10log(I/I0)
    I0= 1.0x10^-12

    I used the 2nd equation given to find the intensity of the sound at 75 db and then plugged that into the 1st equation given to find the power, P. Once I found P, i used the 2nd equation to find the intensity of the sound at 36 dB. I plugged in that number into the 1st equation and solved for r. I feel like I need to involve the frequency to find the answer but I don't know how.
  2. jcsd
  3. Apr 24, 2013 #2
    I don't think the frequency would be an issue
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