What is the "source-filter theory" in speech production?

The source-filter theory is a fundamental concept in speech production that explains how vocal sounds are generated and modified. According to this theory, the vocal folds act as the sound source, producing a fundamental frequency through vibration when air is expelled from the lungs. This sound is then shaped by the vocal tract, which includes the throat, mouth, and nasal passages. The configuration of these structures modifies the sound by enhancing certain frequencies and dampening others, which contributes to the unique qualities of speech sounds.

The correct choice aligns with this understanding of the theory by emphasizing both the role of the vocal folds as the source of the sound and the function of the vocal tract as the filter that shapes the sound quality. This interaction is crucial in understanding how different speech sounds are produced and perceived. The resonance characteristics of the vocal tract also play a vital role in determining the specific sounds that emerge from this process.