What is the period in relation to sound waves?

The correct answer identifies the period of a sound wave as the time it takes for the wave to complete one full cycle. In the context of sound, this refers to the duration it takes for a wave to move from its starting point, reach its peak, return to its baseline, and then complete the cycle by returning to that starting point. This concept is essential in understanding sound waves because the period is inversely related to frequency. When sound waves have a higher frequency, they complete cycles more quickly, resulting in a shorter period.

The other choices do not accurately define the concept of a period. Loudness is related to amplitude, not period, since it describes how strong or intense a sound feels to the listener. Frequency refers to the number of cycles per unit of time and is not the same as period, though they are mathematically related. Delay time in hearing pertains to the perception of sound rather than the technical definition of a wavelength cycle. Thus, recognizing that the period is specifically about the time for a wave to complete a cycle clarifies the fundamental characteristics of sound waves in acoustics.