In sound waves, what is primarily responsible for pitch perception?

Pitch perception in sound waves is primarily determined by frequency. Frequency refers to the number of cycles a sound wave completes in one second, measured in Hertz (Hz). Higher frequencies correspond to higher pitches, while lower frequencies correspond to lower pitches. This relationship is a fundamental aspect of how humans perceive sound; when the frequency increases, we perceive a sound as having a higher pitch, and when it decreases, we perceive a sound as having a lower pitch.

The other options relate to different characteristics of sound but do not primarily influence pitch. Amplitude affects volume—how loud or soft a sound is—rather than its pitch. Reverberation pertains to the persistence of sound in a space, affecting its richness or echo but not the pitch itself. Waveform shape can influence timbre, which is the quality or color of a sound, but it does not determine the pitch. Therefore, frequency is the key factor in pitch perception, making it the correct answer.