MTEL Technology and Engineering

Correct Response: B. When two sound waves are close in frequency, they interfere in such a way that repeating beats can be heard superimposed on the two original tones. The frequency of the beats can be calculated as the difference in the frequencies of the two original sound waves. This is called the beat frequency. In this case, the beat frequency is 90 Hz – 80 Hz = 10Hz. Choice A comes from dividing 80 Hz by 90 Hz, and rounding the result. Choice C is the average of the two original frequencies. Choice D is the sum of the two original frequencies.