Distortion is a sound effect achieved by deformation of a signal by its
“hard” amplitude limitation, or a device providing such an effect.
Sometimes this term refers to a group of similar sound effects (overdrive, fuzz
and others) that realize nonlinear distortion of the signal. They are also
called “overload” effects, and the corresponding devices are
The distortion effect, as a component, is present in
synthesizers, effect processors and computer programs for sound processing.
A large number of harmonics arise in the spectrum of the
distorted signal. Each harmonic represents a sinusoidal oscillation, with a
frequency greater and a multiple of the fundamental frequency. Harmonics of
higher orders are already outside the sound range and have a small amplitude of
oscillations, so they can be neglected. In accordance with the multiplicity,
the harmonics are divided into even and odd. Even harmonics consonant with each
other and with the basic tone, thereby giving the instrument’s timbre volume
and depth. The frequency, for example, of the third harmonic is three times
higher than the frequency of the fundamental tone and corresponds to a note
lying from the fundamental tone at a distance of a fifth through an octave. In
principle, this harmonic can be called a consonant basic tone, but when playing
several notes simultaneously, it can be discordant with another basic tone and
its harmonics. Thus, the odd harmonics of higher orders are less musical and
create “mud” in the sound.
The spectrum of the signal of transistor
“distortors” is rich in odd harmonics, and musicians characterize
such devices with a dissonant “transistor” sound. A different effect
is observed in “distortors” on radio tubes. In the spectrum of their
signal contains a small number of harmonics (dominated by the second, third and
fourth), because of what people perceive it as a softer sound, or as it is
often called – “tube”.
Low notes sound “overloaded” high. In high sounds,
harmonics will increasingly go beyond earshot, while at low frequencies they
are within the frequency range. It should also be borne in mind that the
vibrations of the strings are not pure tones (unless the natural flajulets are
as close to them as possible) and are themselves rich in harmonics. That is, a
complex signal is subjected to distortion and its harmonics generate their
additional harmonics. Obviously, for sounds produced by thick strings, there
are more distinguishable harmonics, and, accordingly, more secondary harmonics
generated by them.
There is also such a phenomenon as intermodulation: two
simultaneously sounding notes cause distortion to produce another sound,
determined by the difference in their frequencies. In the case of two notes,
this sound is in harmony with the two basic notes, but three notes form three
pairs of notes and generate three secondary sounds introducing dissonance.
The difference of distortion from overdrive is expressed by
the fact that it does not matter how strong a blow is struck on the string.
Attack is characterized by a certain level and frequency spectrum of the
signal. So, the distortion attack is not actually allocated (by signal level),
in contrast to overdrive, which has a high level of attack. The frequency
spectrum is distorted even, the attack is somewhat richer in high harmonics
compared to the sustain phase. Sustain is a stretch of sound. Distortion has a
long sustain, often turning into self-excitation. The end of the signal
following the sustain is called attenuation. After the attenuation of the
signal, you can hear the level of the effect’s own noises, or the noise
suppressor will work in pauses. The level of the intrinsic noise of the
distortion effect is usually high due to its high sensitivity.