One independent sound source produces a sound-intensity level of 60 dB at a point. One hundred identical mutually incoherent sources are operated simultaneously at the same distance from the point. If the new sound-intensity level is N dB, find N.
Physics · Wave Motion · beat and properties of sound
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Question

One independent sound source produces a sound-intensity level of 60 dB at a point. One hundred identical mutually incoherent sources are operated simultaneously at the same distance from the point. If the new sound-intensity level is N dB, find N.

Physics · Wave Motion · beat and properties of sound

G1 Physics · Accepted Answer

For mutually incoherent identical sources, intensities add. Thus, I₂ = 100I. The increase in level is Δβ = 10log₁₀100 = 20 dB. Therefore, β₂ = 60+20 = 80 dB. Hence, N = 80.