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Two identical loudspeakers are 3 m apart. A person stands 5.2 m from one speaker and 3 m from the other. What?

Two identical loudspeakers are 3 m apart. A person stands 5.2 m from one speaker and 3 m from the other. What is the lowest frequency at which destructive interference will occur at this point? The speed of sound in air is 343m/s answer in Hz

Public Comments

1. Destructive interference happens when you're off by 0.5, 1.2, 2.5… wavelengths. You can take it from there.
2. P O ................. 3 m ................. O Q ................................* A Person path difference ( ∆) between 2 waves reaching A ∆ = PA - QA = 5.2 - 3 = 2.2 m phase difference = ψ = (2 π / λ) ∆ ψ = (2 π *f/ v) *2.2 --------- (1) ---------------------------------------- I (resultant) = I1 + I2 + 2[I1*I2]^1/2 * cos (ψ) I1=I2 = identical waves I = 2I1 [1 + cos (ψ)] I = 0 for destructive cos ψ = - 1 = cos π (lowest), cos 3 π .......... phase difference = π radians ψ = (2 π *f/ v) *2.2 = π (2 f) *2.2 = v frequency = lowest = f = v/4.4 = 343/4.4 = 77.95 Hz