Savart’s cup demonstrates quarter-wave tube resonance via a bow-driven metal cup

Evidence

Savart’s cup is meant to illustrate resonance of a half-open tube at its lowest, quarter-wave mode. It consists of a metal cup excited to its fundamental, lowest frequency deformation mode by stroking with a violin bow (figure 20.9). The cup oscillates back and forth between slightly ellipsoidal shapes (exaggerated in figure 20.10) with their major axes at 90 degrees to each other. A movable piston inside the tube makes the tube resonance frequencies adjustable. A very similar system involves the simpler apparatus of a graduated cylinder tuned with water, with a tuning fork held above it. The level of the water may be adjusted until the column of air in the cylinder resonates with the frequency of the tuning fork. — Eric J. Heller, Why You Hear What You Hear- An…, 1898

Categorization

Category: Definitional Content

• QUESTION: The water-tuned cylinder with tuning fork is a classic physics demo worth verifying the exact tuning procedure for; could be a hands-on experiment for the hearing question.

Related

• A resonant tube captures and reradiates the near field, defeating acoustic short-circuiting (similarity 0.79)
• Naive resonance matching alone cannot explain Savart’s cup amplification. (similarity 0.79)

Broader Connections

• A quarter-wavelength resonator tube boosts a bar’s fundamental loudness #expands (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1287