Bowing forces errant sharp violin partials into phase-locked even spacing.

Evidence

When a violin string is plucked and the decaying sound recorded, a power spectrum analysis reveals that the partials are not quite evenly spaced. The finite thickness of the string makes it stiff against higher curvature, sharpening the higher partials. Yet when a properly resined bow is moving across the string steadily, a perfectly periodic tone results. The power spectrum must therefore consist of perfectly evenly spaced partials. Apparently, the errant sharp upper partials have been reined in and forced to vibrate at a lower frequency than they want to. This is not an obvious result—one could imagine that all the partials do their vibrating on resonance and therefore impart an aperiodic tone to the bridge. But it is not so. If we assume that some periodic stick-slip will exist; then some modes will be driven slightly off resonance. We know off-resonant driving results in motion at the drive frequency. But the entrainment is more amazing in that the partials are phase-locked. Without phase-locking, the sawtooth shape and organized stick-slip would be lost. — Eric J. Heller, Why You Hear What You Hear- An…, 1760

Categorization

Category: Contrarian or Surprising Claims

• XREF: Relates to entrainment and phase-locking concepts from earlier chapters on resonance and oscillation.
• QUESTION: What physical mechanism enforces the phase-locking that reins in the stiff higher partials?

Related

• Bowing forces stiff-string partials into perfect harmonic alignment through phase-locked entrainment (similarity 0.91)
• Sound phase is inaudible, but bowing depends on phase-shaped physics. (similarity 0.83)
• The violin’s harmonics are phase-locked so their sum produces a traveling kink (similarity 0.82)
• A violin string clamped between steel walls would radiate almost no sound (similarity 0.79)
• Sympathetic plate vibration requires correct phase and location matching (similarity 0.79)
• Upper harmonics swing more in frequency than lower ones during vibrato (similarity 0.79)
• Wind instrument resonances resist aligning into a harmonic series because of impedance-mismatch reflections. (similarity 0.79)
• Harmonic phases in wind instruments are fixed by pulse-driven resonance, not random. (similarity 0.79)
• Bowed strings alternate between stick and slip motion (similarity 0.78)
• Frequency-domain analysis may hide the very properties that make violins great (similarity 0.78)
• Loud brass notes form shock waves requiring precisely phased harmonics. (similarity 0.78)