Loud audible tones require only tiny surface velocities of millimeters per second

Evidence

Fast wave speed does not imply fast motion of the medium carrying the wave. Legions of adjacent small pistons can play the role of the arms of football fans and create potentially fast-moving collective waves while never moving very fast themselves. The speeds attained by vibrating surfaces are normally not very high, even if the waves moving along them are fast: If a section of wall is vibrating in and out as a whole so as to create a very loud, 94 dB, 1000 Hz tone, it has to move at a maximum speed of only about 2 millimeters per second! — Eric J. Heller, Why You Hear What You Hear- An…, 697

Categorization

Category: Contrarian or Surprising Claims

• SEED: The football-stadium wave as a model for how slow individual motions produce fast collective waves — a vivid analogy for explaining wave mechanics to non-specialists.
• CANDY: A 94 dB wall tone only needs the wall to move 2 mm/s — a great bar fact.
• XREF: Connects to the lag between individual piston velocity and collective wave speed; echoes later discussion of wave/particle distinction.

Related

• Fast wave propagation does not require fast motion of the medium itself. (similarity 0.90)
• Even very loud sounds move air by only about a micron. (similarity 0.84)
• Small vibrating objects radiate weak sound because source size is far under one wavelength (similarity 0.79)
• Loudness is not reducible to sound pressure level or signal power (similarity 0.79)
• Piston sound power scales with area squared, not linearly with area (similarity 0.79)
• Loudness depends on more than physical sound intensity alone (similarity 0.79)
• Loud bangs require surface accelerations exceeding one hundred times gravity. (similarity 0.79)
• A small piston still radiates sound because velocity is slightly in phase with force (similarity 0.78)
• Loudness depends on frequency, angle, duration, and envelope, not just level (similarity 0.78)
• Wider bandwidth increases perceived loudness at equal sound pressure (similarity 0.78)
• Loudness scales with frequency squared, requiring large amplitude at low frequencies (similarity 0.78)
• Attaching a small vibrating source to a larger surface boosts loudness by 25 dB. (similarity 0.78)

Broader Connections

• Loudness scales with frequency squared, requiring large amplitude at low frequencies #qualifies (0.80) — Eric J. Heller, Why You Hear What You Hear- An…, 667