Unequal wave amplitudes quickly reduce interference effects below 1 dB peak variation

Evidence

As the number of wavelengths for a fixed distance increases with frequency, this figure shows that the interference at a particular point varies with frequency. If the two waves are not of equal amplitude, then the interference effect is reduced, also as shown in Figure 1.27. In fact, once the interfering wave is less than one eighth of the other wave, then the peak variation in sound pressure level is less than 1 dB. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 365

Categorization

• XREF: The 1/8-amplitude threshold for negligible interference connects to practical acoustic treatment: comb filtering from reflections matters mainly when surfaces reflect strongly.