What is the fundamental frequency in a complex sound?

The fundamental frequency in a complex sound is defined as the lowest frequency of vibration within that sound. It serves as the basic pitch from which other harmonics or overtones are derived. The fundamental frequency is crucial because it determines the perceived pitch of the sound. In many cases, while there are multiple frequencies present in a sound (harmonics), the fundamental frequency is the one that is most significant for pitch recognition.

In the context of complex sounds, each frequency contributes to the overall sound, but the fundamental frequency is the primary reference point for how we perceive that sound's pitch. Other options provided describe different aspects of sound frequencies but do not accurately capture the definition of the fundamental frequency. For instance, referencing the highest frequency only identifies one component of the sound, while mentioning noise production or repetition does not emphasize the pitch importance of the fundamental frequency specifically.