What term describes the variation in pitch of a sound caused by the motion of the source or observer?

The term that describes the variation in pitch of a sound caused by the motion of the source or observer is known as the Doppler Effect. This phenomenon occurs when either the source of sound or the observer is moving relative to each other. As the source approaches the observer, the sound waves are compressed, which increases the frequency and results in a higher pitch. Conversely, as the source moves away, the sound waves are stretched, leading to a lower frequency and thus a lower pitch.

This understanding of the Doppler Effect is critical in various applications, such as in astronomy to determine the speed of stars or galaxies moving toward or away from Earth, and in radar and medical imaging technologies. The concept involves a fundamental interaction between wave behavior and relative motion, highlighting how sound is perceived differently under varying conditions of movement.

The other terms listed do not accurately describe this effect. For instance, sound barrier refers to the limit of speed at which an aircraft can travel without creating a shock wave. Harmonics pertain to the frequencies at which a system responds, usually involving the fundamental frequency and its integer multiples, while frequency shift is a broader term that can pertain to changes in frequency due to various factors, not specifically tied to relative motion in the way the Dop