Which of the following concepts involves frequencies that are multiples of a fundamental frequency?

The concept that involves frequencies that are multiples of a fundamental frequency is harmonics. In acoustics, harmonics refer to the additional frequencies that are produced when an object vibrates. The fundamental frequency is the lowest frequency produced by the vibrating object, and harmonics are the higher frequencies that occur at integer multiples of this fundamental frequency. For instance, if the fundamental frequency is 100 Hz, the first harmonic would be 200 Hz, the second harmonic would be 300 Hz, and so on.

This concept is crucial in understanding sound quality and how musical instruments produce different timbres. By examining the harmonic content of a sound, one can identify its richness or color, which significantly impacts how we perceive sound.