Standing waves create loudness dips at room midpoints

Evidence

When there is a standing wave, it is obvious that the sound level at the frequency of the resonance will change as one moves around the room. In fact, a classic demonstration of the phenomenon is to set up a loudspeaker placed against an end wall radiating a pure tone at the first-order resonance frequency along that dimension of the room, and have listeners walk from one end to the other. In normally reflective rooms, the sound will be about equally loud at both ends of the room and will almost disappear at the halfway point. A variation of this is to have the listeners stand at a single point and scan the signal generator through a range of low frequencies—there will be huge fluctuations in loudness, high at some frequencies, low at others. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1020

Categorization

• SEED: This classic walking-listener demonstration would anchor a piece on how to hear room modes with your own ears.
• corroborated: 2 independent passages support this claim — Toole, Floyd E, Sound reproduction- the acoustics and…, 1020
• XREF: connects to: Sound waves reflecting between two boundaries can form standing waves — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 386; Standing waves arise when wall spacing equals half-wavelength multiples; Room acoustics shift from standing waves to irregular interference as frequency rises — , Toole, Floyd E - Sound reproduction-…, 626 (+3 more)

Broader Connections

• Spatially static resonant modes cause sound level to vary across a room #corroborates (0.90) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1953
• Room acoustics shift from standing waves to irregular interference as frequency rises #qualifies (0.85) — , Toole, Floyd E - Sound reproduction-…, 626
• Room absorption shrinks mode bandwidth and flattens standing wave peaks #expands (0.80)
• Room low-frequency resonances make expensive audio systems sound muddy or boomy #exemplifies (0.75) — Eric J. Heller, Why You Hear What You Hear- An…, 1266