Vocal folds evolved to protect the lungs, not to produce speech sound.

Evidence

Professional singing is a complex task that extends the action of the instrument used for speech. It is salutary to note that the prime function of the vocal folds is to act as a valve to protect the lungs and not to provide the sound source basic to human communication by means of speech and song. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1373

Categorization

• DEEPTHINKING: Reframes the entire human voice as an opportunistic repurposing of a protective valve, which reshapes how you think about speaking and singing as borrowed rather than designed functions.
• XREF: connects to: Human vocal folds evolved as lung-protecting valves, not for communication; The vocal folds vibrate via pressure changes from curved airflow, not the Bernoulli effect — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1325; Speech production reduces to lungs as compressor driving a glottal oscillator through resonating tracts — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 598 (+7 more)

Broader Connections

• Human vocal folds evolved as lung-protecting valves, not for communication #corroborates (1.00)
• The vocal folds vibrate via pressure changes from curved airflow, not the Bernoulli effect #responds-to (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1325
• Speech production reduces to lungs as compressor driving a glottal oscillator through resonating tracts #complicates (0.75) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 598
• Higher closed quotient increases vocal efficiency through reduced lung sound leakage #complicates (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1332
• A huge variety of speech sounds can be made without vocal folds #complicates (0.75)
• Voiced speech originates from airflow through the vibrating vocal folds across the glottis #complicates (0.75) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 548
• Lip constriction lowers the frequencies of all vocal tract formants #complicates (0.75)
• Voiceless sounds arise from varied vocal tract constrictions independent of vocal folds #complicates (0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 1727
• Pressure dynamics make vocal folds close faster than they open #complicates (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1326
• Elastic recoil and momentum, not Bernoulli effect, mainly close the vocal folds #complicates (0.75)