AP Psychology Practice Test 2025 – Comprehensive All-in-One Guide for Exam Success

The pitch of a sound is primarily determined by the frequency of the sound waves. Frequency refers to the number of wave cycles that occur in a given period of time, typically measured in hertz (Hz). Higher frequency sound waves produce higher pitches, whereas lower frequency sound waves result in lower pitches. This relationship between frequency and pitch is fundamental in the study of sound and music perception.

The other options focus on different attributes of sound waves. Amplitude relates to the loudness or intensity of a sound rather than its pitch. The length of sound waves is not a direct measure used in determining pitch; frequency and wavelength are related, but it’s frequency that matters for pitch. Complexity involves the tone quality or timbre of sound and reflects how many frequencies are present, which influences how a sound is perceived but does not determine pitch directly. Therefore, frequency is the key characteristic that defines the pitch of a sound.