Sound waves are longitudinal waves of alternating compression and rarefaction

Evidence

The region where the golf balls are pushed together is known as a “com­ pression” whereas the region where they are pulled apart is known as a “rar­ efaction,” and the golf balls themselves are the propagating medium. In a real propagating medium, such as air, a disturbance would naturally consist of either a compression followed by a rarefaction or a rarefaction followed by a compression in order to allow the medium to return to its normal state. A picture of what happens is shown in Figure 1.2. Because of the way the dis­ turbance moves—the golf balls are pushed and pulled in the direction of the disturbance’s travel—this type of propagation is known as a “longitudinal wave.” Sound waves are therefore longitudinal waves which propagate via a series of compressions and rarefactions in a medium, usually air. — David Howard, Jamie Angus, coustics and Psychoacoustics, 27

Categorization

Category: Definitional Content

• DEFINE: Precise definition distinguishing longitudinal sound waves from transverse waves.
• SHARE: Good refresher for an engineer friend who mixes up longitudinal vs. transverse waves.

Related

• Compressions and rarefactions define sound as a longitudinal wave through a medium. (similarity 0.93)
• Sound propagation can be modeled as coupled masses and springs (similarity 0.84)
• A sound wave’s pressure component arises from the force driving molecular displacement. (similarity 0.83)
• Transverse waves move particles side to side rather than push-and-pull. (similarity 0.83)
• Sound is a mechanical wave requiring a medium and a vibrating source (similarity 0.82)
• Excitation in an elastic medium generates waves from the source (similarity 0.80)
• Sound waves superimpose linearly because their energy flow is preserved. (similarity 0.80)
• Pressure is scalar while velocity gives a sound wave its direction (similarity 0.80)
• Molecular inertia makes air particle velocity change smoothly and continuously (similarity 0.79)
• Sound requires a physical medium and is fundamentally a mechanical disturbance (similarity 0.78)
• Most sound arises from vibrating mechanical objects in a medium (similarity 0.78)

Broader Connections

• Sound propagation can be modeled as coupled masses and springs #expands (0.78) — David Howard, Jamie Angus, coustics and Psychoacoustics, 25