Distortion (acoustics)

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In acoustics , nonlinear distortion is the falsification of an acoustic signal by adding frequencies that are not contained in the original signal.

For the linear distortion see frequency response and equalization .


In the broadest sense, the decay of a vibration is also a linear distortion. In contrast, non- linear distortion adds frequencies to the signal that are not present in the input because the amplifier works like a mixer . These additional frequencies appear as overtones ( harmonics ) or sum and difference frequencies in the spectrum. A change in the waveform of the amplitude can be seen in the time function (Fourier synthesis and analysis). The overtones are predominantly whole-number multiples (= harmonic) of the basic frequency.

Output spectrum of a tube amplifier if the frequencies 34 kHz and 653 kHz are fed in at the same time. Corresponding sum and difference frequencies also occur with other input frequencies.

Overtones arise, for example, during generation , recording or reproduction due to non-linearities of the parts used. The result appears spectrally as if additional frequencies that do not correspond to the fundamental tone were added to a tone . For the sound perception here that are harmonics of the overtone series in charge, that is, the integer multiples of the fundamental frequency - is the level ratio changed these frequencies to each other, the sound changes, this is called harmonic nonlinear distortion. The ratio of the level of the fundamental to the level of the overtone sum is called the distortion factor . If other frequencies arise that are not multiples of the basic frequency, one speaks of non-harmonic, non-linear distortion, which is usually described more sharply and less musically in the auditory impression.

In sound engineering and instrumental music , the unnatural reproduction of sounds can be desirable or undesirable depending on the area of ​​application.

Unwanted distortion

Distortion can occur unintentionally due to the unfavorable shape and natural oscillation of an acoustic resonator or horn ( megaphone ) or due to non-linearities in the electronic pick-up, amplification and reproduction of a sound.

Deliberate distortion

Acoustic distortion

Distortions in the musical sense can already be wanted during instrumental sound generation. In the case of string instruments , such effects can be caused by incorrect painting of the strings , so that the sound is somewhere between normal and harmonics ; with wind instruments one knows the technique of growling (singing into the instrument at the same time while blowing it). The effect manifests itself in the overlapping of the sung and played tone, the interference makes the sound of the instrument appear "dirty". The strength of the effect can be modulated depending on the singing volume and the interval between the played note. A musician who is known for perfecting this technique is the jazz trombonist Albert Mangelsdorff .

Electronic distortion

The intentionally unnatural reproduction of a sound in the music by means of musical effects devices or amplifiers , such as the artistic distortion of the guitar signal in the guitar amplifier , can be achieved, among other things, by a distortion or by overdriving the amplifier.

In the case of electronic distortion, spectral components are also generated that were not present in the original signal. This is especially true when chords are presented via a distortion device. Difference tones can arise (tones whose pitch corresponds to the difference between the tones played) or hum tones (tones whose pitch corresponds to the sum of the tones played), difference and hum tones between the fundamental tone and overtones, etc.


  • Thomas Görne: Sound engineering. 1st edition, Carl Hanser Verlag, Leipzig, 2006, ISBN 3-446-40198-9
  • Roland Enders: The home recording manual. 3rd edition, Carstensen Verlag, Munich, 2003, ISBN 3-910-09825-8

Individual evidence

  1. The Great Brockhaus in 12 volumes . 18th completely revised edition. Wiesbaden 1978. Volume 12

See also

Web links

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