A reflecting wall doubles total sound power output from any source

Evidence

There is an alternative and very simple way of understanding the amplification effects of reflecting surfaces near a sound source: the method of images. We can illustrate this neat trick by returning to a single source near a straight wall. If you shine a flashlight into a mirror, the light bounces off the mirror back into the room. The light in the room is the same as if that image of you holding the flashlight in the mirror is real, pointing the flashlight into the room, with no wall present. The wall can be replaced by an identical, mirror-image “virtual” source symmetrically across the wall. The sound field on the “physical” side of the wall using both the real source and the image source, with the wall removed, is the same as only the real source with the mirror present. It is easy to compare the two approaches in Ripple, which confirms the equivalence. Ray tracing (figure 7.4) also shows that the reflected rays emerge as if from a virtual source symmetrically on the other side of the wall. — Eric J. Heller, Why You Hear What You Hear- An…, 515 (#expands, via linked claim)

Waterhouse (1955) extended work by Rayleigh (1964) and confirmed experimentally that the power output of a source is affected by the presence of boundaries, for example the walls in a room. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134 (#expands, via linked claim)

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)

Categorization

• XREF: connects to: Surface reflection reduces total sound power and favors high frequencies; Reflecting walls are equivalent to mirror-image virtual sound sources — Eric J. Heller, Why You Hear What You Hear- An…, 515; Room boundaries alter a sound source’s radiated power, not just its perceived sound — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134 (+8 more)

Broader Connections

• Reflecting walls are equivalent to mirror-image virtual sound sources #expands (0.90) — Eric J. Heller, Why You Hear What You Hear- An…, 515
• Room boundaries alter a sound source’s radiated power, not just its perceived sound #expands (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2134
• A single sound source near a reflecting surface creates interference via an image source #expands (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 366
• Surface reflection reduces total sound power and favors high frequencies #contradicts (0.80)
• Room boundaries alter loudspeaker output through reflected image sources #expands (0.80)
• Nearby reflecting surfaces constructively pile up wave reflections to amplify sound #corroborates (0.80)
• Each added boundary surface boosts sound intensity by 3 dB up to three boundaries #corroborates (0.75)