A parabolic mirror focusing sun also focuses a distant voice

Evidence

Several acoustical situations can cause interference effects. The obvious ones are when two loudspeakers radiate the same sound into a room or when the same sound is coupled into a room via two openings that are separated. A less obvious situation is when there is a single sound source spaced away from a reflecting boundary, either bounded or unbounded. In this situation, an image source is Position (in wavelengths) or relative frequency FIGURE 1. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 366 (#expands, via linked claim)

Diffuse surfaces, on the other hand, scatter sound in other directions than the specular. In the case of an ideal diffuser, the scattered energy polar pattern would be in the form of a hemisphere. A simple approach to calculating the effect of this can be to model the scattered energy as a source whose initial intensity is given by the incident energy. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2318 (#contradicts, via linked claim)

Categorization

• XREF: connects to: Mirrors can magnify tiny oscillations into large visible light-beam excursions; A single sound source near a reflecting surface creates interference via an image source — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 366; Diffuse surfaces scatter sound hemispherically rather than mirror-like — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2318

Broader Connections

• Mirrors can magnify tiny oscillations into large visible light-beam excursions #exemplifies (0.82)
• A single sound source near a reflecting surface creates interference via an image source #expands (0.80) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 366
• Diffuse surfaces scatter sound hemispherically rather than mirror-like #contradicts (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2318