Sound in air travels at one speed for all wavelengths, unlike water waves

Evidence

In air, all wavelengths of sound travel at the same speed. If this were not so, speech would become unintelligible some distance from the speaker, with the higher-frequency, shorter-wavelength components of speech arriving before or after the lower-frequency ones. Not all types of waves obey this equal-speed rule—for example, surface water waves traveling over deep water propagate at a speed proportional to the square root of their wavelength, so at a distance from the source of a sudden disturbance, the long wavelengths arrive first. Anyone who has spent extensive time on the water will have noticed that the longer-wavelength waves from a distant ship arrive before the shorter ones. — Eric J. Heller, Why You Hear What You Hear- An…, 135

Categorization

• XREF: Explains why dispersion destroys intelligibility — connects directly to the reader’s noise/communication books and to how distant speech degrades.