Figure P.1 shows an output pattern that was measured by a • tiny microphone when two small...

Figure P.1 shows an output pattern that was measured by a • tiny microphone when two small piezo-loudspeakers separated by 15 cm were pointed toward the microphone at a distance of 1.5 m away. Given that the speed of sound at 20°C is 343 m/s, determine the approximate frequency at which the speakers were driven. Discuss the nature of the pattern and explain why it has a central minimum.

Figure P.1 (Data courtesy of CENCO.)