 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Sympathetic resonance" – news ·newspapers ·books ·scholar ·JSTOR(August 2016) (Learn how and when to remove this message) |
Sympathetic resonance orsympathetic vibration is aharmonic phenomenon wherein a passive string or vibratory bodyresponds to external vibrations to which it has a harmonic likeness.[1] The classic example is demonstrated with two similarly-tunedtuning forks. When one fork is struck and held near the other, vibrations are induced in the unstruck fork, even though there is no physical contact between them. In similar fashion,strings will respond to the vibrations of a tuning fork when sufficient harmonic relations exist between them. The effect is most noticeable when the two bodies are tuned in unison or an octave apart (corresponding to the first and secondharmonics, integer multiples of the inducing frequency), as there is the greatest similarity in vibrational frequency. Sympathetic resonance is an example ofinjection locking occurring betweencoupled oscillators, in this case coupled through vibrating air. In musical instruments, sympathetic resonance can produce both desirable and undesirable effects.
According toThe New Grove Dictionary of Music and Musicians:[2]
The property of sympathetic vibration is encountered in its direct form in room acoustics in the rattling of window panes, light shades and movable panels in the presence of very loud sounds, such as may occasionally be produced by a full organ. As these things rattle (or even if they do not audibly rattle) sound energy is being converted into mechanical energy, and so the sound is absorbed. Wood paneling and anything else that is lightweight and relatively unrestrained have the same effect. Absorptivity is at its highest at the resonance frequency, usually near or below 100 Hz.
Sympathetic resonance has been applied to musical instruments from many cultures and time periods, and tostring instruments in particular. In instruments with undamped strings (e.g.harps,guitars andkotos), strings will resonate at theirfundamental orovertone frequencies when other nearby strings are sounded. For example, an A string at 440 Hz will cause an E string at 330 Hz to resonate, because they share an overtone of 1320 Hz (the third harmonic of A and fourth harmonic of E). Sympathetic resonance is a factor in thetimbre of a string instrument.
Certain instruments are built withsympathetic strings, auxiliary strings which are not directly played but sympathetically produce sound in response to tones played on the main strings. Sympathetic strings can be found on Indian musical instruments such as thesitar, Western Baroque instruments such as theviola d'amore and folk instruments such as thehurdy-gurdy andHardanger fiddle. Somepianos are built with sympathetic strings, a practice known asaliquot stringing. Sympathetic resonance is sometimes an unwanted effect that must be mitigated when designing an instrument. For example, to dampen resonance in the headstock, someelectric guitars usestring trees near their tuning pegs. Similarly, the string length behind thebridge must be made as short as possible to dampen resonance.
| Acoustical engineering | ||
|---|---|---|
| Psychoacoustics | ||
| Audio frequency andpitch | ||
| Acousticians | ||
| Related topics | ||
