Timbre

Overview

In music, timbre (Template:PronEng, Template:IPA like timber, or Template:IPA, from Fr. timbre Template:IPA) is the quality of a musical note or sound that distinguishes different types of sound production, such as voices or musical instruments. The physical characteristics of sound that mediate the perception of timbre include spectrum and envelope. Timbre is also known in psychoacoustics as sound quality or sound color.

For example, timbre is what, with a little practice, people use to distinguish the saxophone from the trumpet in a jazz group, even if both instruments are playing notes at the same pitch and amplitude. Timbre has been called "a wastebasket category", or "the psychoacoustician's multidimensional wastebasket category" as it can denote many apparently unrelated aspects of a sound.

History

The Chinese developed a sophisticated understanding of the musical quality of timbre during the Song Dynasty. They discovered that the timbre of string instruments could be changed depending on how the strings were touched. Strings could be plucked, brushed, hit, scraped, or rubbed to produce different sounds. The Chinese composed music on the Qin, a long, wooden board with strings. Their Qin songs emphasized the timbre, and the changes in sound could be heard throughout the song.

Synonyms

Tone quality is used as a synonym for timbre.

Tone color is also often used as a synonym. People who experience synesthesia may see certain colors when they hear particular instruments. Helmholtz used the German Klangfarbe (tone color), and Tyndall proposed an English translation, clangtint. But both terms were disapproved of by Alexander Ellis who also discredits register and color for their pre-existing English meanings (Erickson 1975, p.7).

Colors of the optical spectrum are not generally explicitly associated with particular sounds. Rather, the sound of an instrument may be described with words like "warm" or "harsh" or other terms, perhaps suggesting that tone color has more in common with the sense of touch than of sight. However, color is often used to describe different types of noise such as pink or white. Noise color is determined by mixing together parts of the visible light spectrum that correspond to the audible sound spectrum. A 20 hertz tone is subsonic and a 20000 hertz tone is ultrasonic, so pink noise is pink because it contains loud low-frequency noise mixed with quieter broadband noise.

American Standards Association definition

The American Standards Association defines timbre as "[...] that attribute of sensation in terms of which a listener can judge that two sounds having the same loudness and pitch are dissimilar". A note to the 1960 definition (p.45) adds that "timbre depends primarily upon the spectrum of the stimulus, but it also depends upon the waveform, the sound pressure, the frequency location of the spectrum, and the temporal characteristics of the stimulus."

Attributes

J.F. Schouten (1968, p.42) describes the "elusive attributes of timbre" as "determined by at least five major acoustic parameters" which Robert Erickson (1975) finds "scaled to the concerns of much contemporary music":

1. The range between tonal and noiselike character.
2. The spectral envelope.
3. The time envelope in terms of rise, duration, and decay.
4. The changes both of spectral envelope (formant-glide) and fundamental frequency (micro-intonation).
5. The prefix, an onset of a sound quite dissimilar to the ensuing lasting vibration.

Spectra

The richness of a sound or note produced by a musical instrument is sometimes described in terms of a sum of a number of distinct frequencies. The lowest frequency is called the fundamental frequency and the pitch it produces is used to name the note. For example, in western music, instruments are normally tuned to A = 440 Hz. Other significant frequencies are called overtones of the fundamental frequency, which may include harmonics and partials. Harmonics are whole number multiples of the fundamental frequency — ×2, ×3, ×4, etc. Partials are other overtones. Most western instruments produce harmonic sounds, but many instruments produce partials and inharmonic tones, such as cymbals and other non-pitched instruments.

When the orchestral tuning note is played, the sound is a combination of 440 Hz, 880 Hz, 1320 Hz, 1760 Hz and so on. The balance of the amplitudes of the different frequencies is responsible for the characteristic sound of each instrument.

The fundamental is not necessarily the strongest component of the overall sound. But it is implied by the existence of the harmonic series — the A above would be distinguishable from the one an octave below (220 Hz, 440 Hz, 660 Hz, 880 Hz) by the presence of the third harmonic, even if the fundamental were indistinct. Similarly, a pitch is often inferred from non-harmonic spectra, supposedly through a mapping process, an attempt to find the closest harmonic fit.

It is possible to add artificial 'subharmonics' to the sound using electronic effects but, again, this does not affect the naming of the note.

William Sethares (2004) wrote that just intonation and the western equal tempered scale derive from the harmonic spectra/timbre of most western instruments. Similarly the specific inharmonic timbre of Thai metallophones would produce the seven-tone near-equal temperament they do indeed employ. The five-note sometimes near-equal tempered slendro scale provides the most consonance in the combination of the inharmonic spectra of Balinese metallophones with harmonic instruments such as the stringed rebab.

Envelope

The timbre of a sound is also greatly affected by the following aspects of its envelope: attack time and characteristics, decay, sustain, release (ADSR envelope) and transients. Thus these are all common controls on synthesizers. For instance, if one takes away the attack from the sound of a piano or trumpet, it becomes more difficult to identify the sound correctly, since the sound of the hammer hitting the strings or the first blat of the player's lips are highly characteristic of those instruments. The envelope is the overall amplitude structure of a sound, so called because the sound just "fits" inside its envelope: what this means should be clear from a time-domain display of almost any interesting sound, zoomed out enough that the entire waveform is visible.

In music

Timbre is often cited as one of the fundamental aspects of music. Formally, timbre and other factors are usually secondary to pitch. "To a marked degree the music of Debussy elevates timbre to an unprecedented structural status; already in L'Apres-midi d'un Faune the color of flute and harp functions referentially," according to Jim Samson (1977). Surpassing Debussy is Klangfarbenmelodie and surpassing that the use of sound masses.

Erickson (ibid, p.6) gives a table of subjective experiences and related physical phenomena based on Schouten's five attributes:

Subjective	Objective
Tonal character, usually pitched	Periodic sound
Noisy, with or without some tonal character, including rustle noise	Noise, including random pulses characterized by the rustle time (the mean interval between pulses)
Coloration	Spectral envelope
Beginning/ending	Physical rise and decay time
Coloration glide or formant glide	Change of spectral envelope
Microintonation	Small change (one up and down) in frequency
Vibrato	Frequency modulation
Tremolo	Amplitude modulation
Attack	Prefix
Final sound	Suffix

Often listeners are able to identify the kind of instrument even across "conditions of changing pitch and loudness, in different environments and with different players." In the case of the clarinet, an acoustic analysis of the waveforms shows they are irregular enough to suggest three instruments rather than one. David Luce (1963, p.17) suggests that this implies "certain strong regularities in the acoustic waveform of the above instruments must exist which are invariant with respect to the above variables." However, Robert Erickson argues that there are few regularities and they do not explain our "powers of recognition and identification." He suggests the borrowing from studies of vision and visual perception the concept of subjective constancy. (Erickson 1975, p.11)

Spelling

Though timber is accepted, the more common spelling is timbre to distinguish the word from timber ("wood").

See also

• Formant

Further reading

• Stephen David Beck. "Designing Acoustically Viable Instruments in Csound" in Boulanger, Richard. The Csound Book.
• Paolo Prandoni, then graduate student, wrote two papers on timbre, available here: http://lcavwww.epfl.ch/~prandoni/Research/timbre.html

Sources

• Erickson, Robert (1975). Sound Structure in Music. University of California Press. ISBN 0-520-02376-5.
• American Standards Association (1960). American Standard Acoustical Terminology. New York. Definition 12.9, Timbre, p.45.
• Luce, David A. (1963). "Physical Correlates of Nonpercussive Musical Instrument Tones", Ph.D. dissertation. MIT.
• McAdams, Stephen, and Albert Bregman (1979). "Hearing Musical Streams". Computer Music Journal 3, no. 4 (December): 26–43.
• Schouten, J. F. (1968). "The Perception of Timbre". Reports of the 6th International Congress on Acoustics, Tokyo, GP-6-2. Pp. 35-44, 90.
• Samson, Jim (1977). Music in Transition: A Study of Tonal Expansion and Atonality, 1900-1920. New York: W.W. Norton & Company. ISBN 0-393-02193-9.
• Sethares, William (2004). Tuning, Timbre, Spectrum, Scale. Springer, ISBN 3-540-76173-X.