Materials with movable boundaries support wave types beyond longitudinal waves.

Evidence

There are three main types of wave in these structures: quasi-longitudinal, transverse shear and bending (flexural)—the latter two are shown in Figures 1.3 and 1.4. There are others, for example surface acoustic waves, like waves at sea and waves in earthquakes, that are combinations of longitudinal and transverse waves. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 105 (#expands, via linked claim)

It is difficult to generate pure shear waves in a plate via the use of applied forces because in practice an applied force results in both lateral and longitudinal displacements. This has the effect of launching bending (flexural) waves into the plate. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 121 (#expands, via linked claim)

From Figure 1.5, we can see that both the quasi-longitudinal and transverse shear waves in bars and plates are nondispersive. That is, their phase velocity is independent of frequency. This means that they also have a frequency-independent group velocity and therefore preserve the waveshape of a sound wave containing many frequency components. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132 (#expands, via linked claim)

Categorization

• XREF: connects to: Solid structures carry three main wave types plus hybrid surface waves — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 105; Shear waves resist deformation via stiffness rather than tension; Applied forces in plates generate bending waves rather than pure shear waves — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 121 (+2 more)

Broader Connections

• Solid structures carry three main wave types plus hybrid surface waves #expands (0.82) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 105
• Applied forces in plates generate bending waves rather than pure shear waves #expands (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 121
• Longitudinal and shear waves preserve waveshape because phase velocity is frequency-independent #expands (0.75) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 132
• Shear waves resist deformation via stiffness rather than tension #expands (0.72)
• Sound waves are longitudinal waves of alternating compression and rarefaction #exemplifies (0.72)