Residual tone

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Residual sound or residual (from Latin residuum 'rest' ) is a term introduced by Jan Frederik Schouten for a psychoacoustic phenomenon.

When an acoustic signal is presented in the form of a periodic oscillation , in which the fundamental tone is only very weak or not present at all, the perception of a pitch that corresponds to this missing fundamental tone nevertheless arises . In terms of timbre, too , the lack of the fundamental is often felt less clearly than would be expected. This "added" keynote is called the residual tone .

Explanation

The superposition of two oscillations (e.g. 200  Hz and 300 Hz) results in an oscillation with the frequency of the residual tone of 100 Hz

There are two main effects that explain the phenomenon of residual tones:

  • According to a widely held theory of the last few decades, the central core of the inferior colliculus in the auditory midbrain of mammals determines the pitch of the fundamental tone of complex tones, such as animal sounds , vowels and tones of musical instruments. It is assumed here that the lower harmonic partials of the complex tones in the frequency band layers ( laminae ) of the above Core area isolated and the matching periodicity of the signals of several laminae filtered out by neural periodicity detectors.

application

Organ building

The phenomenon of residual tones has long been used in organ building with so-called acoustic registers : If the 8-foot and 5 1 / 3- foot, which is a fifth above, are used at the same time , one hears the 16-foot, i.e. an octave below 8 feet. A missing fundamental tone can be simulated by having two tone generators sounding on the octave and the pure duodecime for the fundamentally nonexistent fundamental tone. In the case of the organ, B. 32' a register saved by a 16'-labial stops with a (preferably covered) 10 (preferably open) 2 / 3 is combined '-Labialregister.

Other instruments

In bagpipes and hurdy-gurdy hurdy-gurdy , the drones are often tuned to a fifth, which means that the resulting residual tone provides additional sound.

In the case of bells , the nominal / strike tone cannot be physically measured, but it is still perceived because it is made up of the partials octave, duodecime and possibly double octave.

With string instruments , the fundamental tones of the low tones are often very weak, but are nevertheless clearly perceived by the audience.

Influence of low tones on the auditory impression

From the possibility of the hearing to derive the fundamental tone of a strictly periodic oscillation, even if this is only weakly transmitted or not transmitted at all, some conclude that transmission of deep tones is unnecessary. However, this is too limited a view.

So is z. B. on the telephone the lower frequency limit at 300 Hz, so the fundamental tone range of adult speakers is hidden. However, the pitch of the voice is recognized by the ear. However, the characteristic of the timbre is lost, the sound of a telephone voice differs considerably from the original.

A strictly periodic signal is a mathematical borderline case that i. a. is not found in nature and can only be represented with sufficient accuracy using electronic means. For this reason, there are usually non-periodic or noisy components in sound events , in which a fundamental tone cannot even theoretically be spoken of. It is therefore very difficult to recognize ambient noise on the phone.

If the low tones are missing during transmission, z. For example, certain instruments in the orchestra or certain organ registers are no longer audible, which significantly changes the character of music. This becomes clear when you switch directly from a linear reproduction down to 20 Hz to a high-pass filtered reproduction.

Large rooms have fashions that lie in these deep areas and that are quietly stimulated by environmental noises and always resonate. This makes up a large part of the feeling of space that one z. B. has when entering a cathedral . The lack of low-frequency information also distorts the perception of space.

Low frequency components often determine the character of certain styles of music ( drum and bass ) or acoustic events (e.g. distant explosions, thunder, ground vibrations), which is why the lack of bass, which is typical for poor sound reproduction, is particularly disadvantageous. The examples mentioned do not contain any harmonics that could be used to synthesize a residual tone.

See also

literature

Individual evidence

  1. ↑ Xiaoqin Wang, Daniel Bendor: Pitch . In: Adrian Rees, Alan Palmer (Eds.): The Oxford Handbook of Auditory Science. The Auditory Brain . Oxford University Press, 2010, ISBN 0-19-923328-4 , pp. 149–172 , here pp. 157–159 (English).
  2. ↑ Line spectra of a flute, a clarinet, an oboe, a trumpet and the G-string of a violin. Studio for Electronic Music, Mozarteum University Salzburg, accessed on August 29, 2019 .