Proximity to a resonator suppresses, rather than amplifies, monopole sound sources
Evidence
The NFC mechanism was well understood by Lord Rayleigh. However, it seems that ever since Rayleigh, the usual casual explanations, something like “there is a resonator near a source and it resonates! Resonators get loud on resonance!” have gradually dulled the mind and the level of understanding. The difficulty with the casual statement is that it is not an explanation, and, worse, it is false in some circumstances. For example, there can be a suppression of the sound if a monopole source, instead of a dipole or quadrupole source, is brought near the resonator. Capture, phase shifting, and reradiation still occurs, but now the phase-shifted, reradiated sound finds itself more or less destructively interfering with the direct sound from the monopole, depending on its distance to the resonator. It is quite shocking to hear this failure if one believes that any sound source should be amplified by proximity to a resonator. Dramatic amplification follows only from breaking a short-circuiting sound source. — Eric J. Heller, Why You Hear What You Hear- An…, 1889
Categorization
- QUESTION: Worth chasing: the commonsense ‘resonators amplify everything’ belief is literally backwards for monopole sources — a striking counterintuitive auditory phenomenon.
- corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 1889
- XREF: connects to: Wall proximity alternately boosts or suppresses a source depending on phase.; Horn confinement amplifies siren output via proximity resonance.; Adjacent compression and rarefaction regions can short-circuit and kill radiated sound (+5 more)
Broader Connections
- Room boundaries alter a sound source’s radiated power, not just its perceived sound
#expands(0.78) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134