ASA 29 - Effect Of Tone Envelope On Timbre

Description

The purpose of this demonstration (originally presented by J. Fassett) is to show that the temporal envelope of a tone, i.e. the time course of the tone's amplitude, has a significant influence on the perceived timbre of the tone. A typical tone envelope may include an attack, a steady-state, and a decay portion (e.g., wind instrument tones), or may merely have an attack immediately followed by a decay portion (e.g., plucked or struck string tones). By removing the attack segment of an instrument's sound, or by substituting the attack segment of another musical instrument, the perceived timbre of the tone may change so drastically that the instrument is no longer recognizable.

In this demonstration, a four-part chorale by J.S. Bach ("Als der gutige Gott") is played on a piano and recorded on tape. Next the chorale is played backward on the piano from end to beginning, and recorded again. Finally the tape recording of the backward chorale is played in reverse, yielding the original (forward) chorale, except that each note is reversed in time. The instrument does not sound like a piano any more, but rather resembles a kind of reed organ. The power spectrum of each note, measured over the note's duration, is not changed by temporal reversal of the tone.

References

K.W.Berger (1963), "Some factors in the recognition of timbre," J. Acoust. Soc. Am. 36, 1888-1891.

M.Clark, D.Luce, R.Abrams, H.Schlossberg and J.Rome (1964), "Preliminary experiments on the aural significance of parts of tones of orchestral instruments and on choral tones," J. Audio Eng. Soc. 12, 28-31.

J.Fassett, "Strange to your Ears," Columbia Record No. ML 4938.

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Transcript

You will hear a recording of a Bach chorale played on a piano.

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Now the same chorale will be played backwards.

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Now the tape of the last recording is played backwards so that the chorale is heard forward again, but with an interesting difference.