Shear waves stay non-dispersive while bending waves disperse with frequency

Evidence

Two points are of note from Equations 1.15 and 1.16. The first is that the wavenumber of lateral shear waves is proportional to frequency, just as one would expect from a non-dispersive wave. However, for a bending wave Calculate the frequency of sound with a wavelength of 34 cm in air at 20°C. — David Howard, Jamie Angus, coustics and Psychoacoustics, 135

Figure 1.5 shows a comparison of the velocity of the different kinds of waves as a function of frequency for an aluminum plate that is 6 cm thick. … However, bending waves are dispersive. That is, their phase velocity is dependent on frequency. This means that they also have a frequency-dependent group velocity and therefore do not preserve the waveshape of a sound wave containing many frequency components. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132

Categorization

• QUESTION: The excerpt cuts off at the bending-wave contrast — worth returning to see exactly how bending-wave dispersion differs.
• DEFINE: Contrast pair cleanly defines dispersive vs nondispersive wave propagation through phase/group velocity and waveshape preservation.
• corroborated: 3 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 135; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132