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Homework Help: Physics with Application; Acoustics; Trumpet

  1. Jan 25, 2012 #1
    From Acoustics, Resonance, Energy, Power, Intensity and The Doppler Effect
    1. The problem statement, all variables and given/known data

    An old-fashioned hearing trumpet has the shape of a flared funnel, with a diameter of 8 cm at its wide end and a diameter of 0.7 cm at its narrow end. Suppose that all of the sound energy that reaches the wide end is funneled into the narrow end. By what factor does this hearing trumpet increase the intensity of sound (measured in W/m2)? By how many decibels does it increase the intensity level of sound?

    2. Relevant equations

    Intensity = Power / Area

    Intensity = Energy / (Time)*(Area)

    Intensity Level = 10*Log(Intensity/10^(-12)) (db)

    3. The attempt at a solution

  2. jcsd
  3. Jan 25, 2012 #2


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    Homework Helper

    Welcome to PF!
    We have a policy of ignoring questions where there is no attempt made on the problem. But I can make an exception since it is your first post, and offer a suggestion to get you started.

    Start by finding the areas, at the input end and at the output to ear end. Put them into your formulas.
  4. Jan 25, 2012 #3
    ... Thanks for the insightful reply. I understand it's not the most difficult question, nonetheless I am getting stuck.

  5. Jan 25, 2012 #4


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    Homework Helper

    I don't understand that at all.
    Were you able to find the two areas?
    Maybe use intensity = power/area twice, once for each end.
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