A quarter-wavelength resonator tube boosts a bar’s fundamental loudness

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 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Savart’s cup demonstrates quarter-wave tube resonance via a bow-driven metal cup; An open mouth amplifies faint sounds by serving as a resonant chamber — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 191

Related

• An open mouth amplifies faint sounds by serving as a resonant chamber (similarity 0.86)
• Savart’s cup demonstrates quarter-wave tube resonance via a bow-driven metal cup (similarity 0.84)
• A vocal tract constriction at the mouth forms a Helmholtz resonator (similarity 0.82)
• A bare vibrating string is nearly inaudible; the instrument body amplifies it (similarity 0.79)
• The ear canal acts as a quarter-wavelength resonator amplifying 3-4 kHz by 10 dB (similarity 0.78)

Broader Connections

• An open mouth amplifies faint sounds by serving as a resonant chamber #corroborates (0.72) — Gordon Hempton, John Grossmann, One Square Inch of Silence- One Man’s…, 191