Distortion

In acoustics, a distinction linear and nonlinear distortion. Here, the nonlinear distortions are described.

The linear distortions see frequency response and equalization.

Basics

In the broadest sense, is the decay of an oscillation, a linear distortion. In contrast, adding non-linear distortion to the signal frequencies, which will not present in the input, because the amplifier operates as a mixer. These additional frequencies appear as overtones (harmonics) or sum and difference frequencies in the spectrum. Here, in the time function of a change in waveform of the amplitude recognizable (Fourier synthesis and analysis). The overtones are predominantly integer multiples ( = harmonic ) of the fundamental frequency.

Harmonics arise, for example in the production, recording or playback by nonlinearities of the parts used. The result will appear spectrally as if a tone additional frequencies which do not correspond to the root, were added. While the harmonics of the overtone series are responsible for the perception of sound, that is the integer multiples of the fundamental frequency - is changing the level ratio of these frequencies to each other, the sound, it is called harmonic nonlinear distortion changes. The ratio of the level of the fundamental to the overtone level sum called this distortion. Is subject to other frequencies are not multiples of the fundamental frequency is called the non-harmonic nonlinear distortion, which are described in most listening impression sharper and unmusical.

In the sound and instrumental music, the unnatural reproduction of sounds desirable depending on the application or undesirable.

Unwanted distortion

Distortion may unintentionally by the awkward shape and natural frequency of an acoustic resonator or horn ( megaphone ) or come about. Due to nonlinearities in the electronic loss, amplification and reproduction of a sound

Intentional distortion

Acoustic distortion

Even with the instrumental sound production distortions in the musical sense can be intentional. For stringed instruments such effects can be caused by incorrect painting of the strings, so that the sound between the normal sound and harmonics is; On wind instruments, one knows the technique of Growling (simultaneous in- the - instrument - singing, while it blows on ). The effect manifests itself in superpositions of the sung and played note, the interference can be the sound of the instrument appear "dirty". The strength of the effect can be modulated to the tone played, depending on the Sing- volume and interval distance. A musician who is known for perfecting this technique, the jazz trombonist Albert Mangelsdorff.

Electronic distortion

The wanted unnatural reproduction of a sound in the music by musical effects devices or amplifiers, such as the artistic distortion of the guitar signal in the guitar amplifier can be accomplished by, inter alia distortion or overdriving the amplifier.

In case of electronic distortion and spectral components are generated, which were not present in the original signal. This is especially true when chords are presented on a distortion box. Differences can arise tones (sounds whose pitch of the difference between the tones played equivalent ) or Sum tones (sounds whose pitch of the sum between the tones played equivalent ), difference and sum tones between the fundamental and overtones, etc..