What does cul-de-sac resonance refer to?

Cul-de-sac resonance specifically refers to a type of resonance characterized by sound being trapped in a particular area within the vocal tract, typically due to certain structural abnormalities. In this case, the resonance occurs in a cavity—such as the pharynx or orally—where sound waves are produced but have limited ability to exit. This results in a muffled or "hollow" quality to the voice, as the sound waves do not resonate freely in the desired manner.

This phenomenon is commonly associated with individuals who have conditions affecting their oral cavity or pharynx, such as macroglossia (enlarged tongue) or certain types of cleft palate. The sound produced can be more confined, thereby limiting how effectively it resonates. The correct understanding of this concept helps distinguish it from other types of resonance, which involve sound being effectively released or articulated differently.