Coupled Resonators
Energy transfer between objects creates organic, irregular decay, unlike the smooth exponential decay of a single resonator.
Energy Shuttles
Pluck a guitar string and energy moves to the body, reflects back, moves again. This back-and-forth creates the complex, evolving decay that makes acoustic instruments sound alive. A single resonator decays smoothly toward silence. Two coupled resonators trade energy: one gets louder while the other gets quieter, then they swap. The result is the beating, irregular sustain that no single oscillator can produce.
Sympathetic Strings
Play one string and nearby strings at related pitches vibrate in sympathy. This is the piano sustain pedal: lift all dampers and every string is free to resonate. A sitar has dedicated sympathetic strings that ring whenever the main strings excite their frequencies. The effect adds a shimmering, reverberant halo around every note.
Try it: pluck String 1 with coupling at zero, then increase coupling to hear energy transfer to String 2. Try "Unison Beating" for the classic coupled-string effect, or "Sympathetic Piano" for four resonating strings.
References
- Sympathetic string, Wikipedia
- Coupled oscillation, Wikipedia
- Physical Audio Signal Processing, Julius O. Smith, Stanford CCRMA