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S K
S K asked in Science & MathematicsPhysics · 1 decade ago

pain from sound?

At a distance of 13 km, a 140 Hz horn, assumed to be a point source, is barely audible. At what distance would it begin to cause pain? (Pain Threshold = 120dB)

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  • benaddict
    1 decade ago
    Favorite Answer

    0.04111 km.

    Using Intensity (in dB) = 10 log_10(I/I_0), where I_0 = 10^(-12)

    Barely perceptible sound = 0 dB, hence I = 10^(-12) Watt

    Now power of the point source is P= I(4 pi R^2) where R = 13000 meters.

    Now Intensity at R2 distance is 120 dB, so I2 = 1 Watt

    Equating power of the source as constant in both locations

    I(4 pi R^2) = I2 (4 pi R2^2)

    giving a value of 0.04111 km for R2.

    Source(s): http://www.ajdesigner.com/phpsound/sound_wave_equa...
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