An open mouth amplifies faint sounds by serving as a resonant chamber

Evidence

This humming sound is so delicate that it cannot stand up to the slightest noise intrusion. Even the listener must remain absolutely quiet—no talking, no foot or arm movements, and quiet, slow breaths with open mouth. I believe an open mouth improves hearing for two reasons: it straightens the auditory canal and it enables the mouth to serve as a resonant chamber, amplifying faint sounds to more audible levels. This is exactly what children do instinctively when the lights go out: the jaw drops and faint sounds are more easily heard. — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 191

Categorization

• QUESTION: Is the straightening-of-the-auditory-canal claim physiologically accurate? Some accounts say mouth-open hearing relates to Eustachian tube patency.
• corroborated: 2 independent passages support this claim — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 191
• XREF: connects to: A resonant cavity can isolate a single frequency from complex sound. — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 920; The hearing system actively filters and modulates sound more than passively receiving it — George Michelsen Foy, Zero Decibels: The Quest for Absolute…, 558; A room’s fundamental resonance can be found by singing different notes. — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 919 (+7 more)

Broader Connections

• The hearing system actively filters and modulates sound more than passively receiving it #expands (0.60) — George Michelsen Foy, Zero Decibels, 558
• A resonant cavity can isolate a single frequency from complex sound. #expands (0.50) — Schafer, Murray R, The Soundscape- Our Sonic Environment…, 920