Two identical loudspeakers are located at points A and B, 2.00 m apart. The loud-speakers are driven by the same amplifier and produce sound waves with a frequency of 784 Hz. Take the speed of sound in air to be 344 m/s. A small microphone is moved out from point B along a line perpendicular to the line connecting A and B (line BC in ?Fig. P16.65?). (a) At what distances from B will there be ?destructive interference? (b) At what distances from B will there be ?constructive interference? (c) 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?

Solution 70P Step 1: The frequency of the sound waves created by two of the speakers is 784 Hz. The speed of the sound waves in air is 344 m/s. So, as we know that, velocity = frequency × wavelength wavelength = 344 / 784 = 0.438 m