Hearing & Orthopedic Care

Sound and Hearing?

Two identical loudspeakers are located at points A and B, 2.00m apart. The loudspeakers are driven by the same amplifier and produce sound waves with a frequency of 784Hz. Take the speed of sound in air to be 344m/s. A small microphone is moved out from point B along a line perpendicular to the line connecting A and B.

If the frequency is made low enough, there will be no positions along the line BC at which destructive interference occurs. How low must the frequency be for this to be the case?

both waves must be counter-phased at a given point. This could be attained when 2m/lamvda = integer N, but at 784Hz lambda = 344/784 =0.44m and N=2/0.44 =4.55; now if N=4 then lamvda =2m/N = 2/4 =0.5m, hence v=c/lamvda = 344/0.5 = 688Hz;

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