Distortion synthesis
Encyclopedia
Distortion synthesis is a group of sound synthesis techniques which modify existing sounds to produce more complex sounds (or timbres), usually by using non-linear
circuits
or mathematics.
While some synthesis methods achieve sonic complexity by using many oscillator
s, distortion
methods create a frequency spectrum
which has many more components than oscillators.
Jean-Claude Risset
was one notable pioneer in the adoption of distortion methods.
Some distortion techniques are: FM synthesis, waveshaping synthesis, and discrete summation formulas.
distorts the carrier frequency
of an oscillator by modulating
it with another signal. The distortion can be controlled by means of an index
.
The method known as phase distortion synthesis
is similar to FM.
synthesis changes an original waveform by responding to its amplitude
in a non-linear fashion. It can generate a bandwidth-limited spectrum, and can be continuously controlled with an index.
The clipping
caused by overdriving an audio amplifier
is a simple example of this method.
(This method should not be confused with wavetable synthesis
, which creates sound from lists of numbers, most often representing one period or cycle per wave. However, wavetable synthesis is identical to the special case of waveshaping synthesis where the original waveform is a sawtooth wave
.)
ic synthesis methods which use mathematical formulas to sum, or add together, many numbers to achieve a desired wave shape. This powerful method allows, for example,synthesizing a 3-formant voice in a manner similar to FM voice synthesis. DSF allows the synthesis of harmonic
and inharmonic, band-limited or unlimited spectra, and can be controlled by an index. As Roads points out, by reducing digital synthesis of complex spectra to a few parameters, DSF can be much more economical.
Nonlinearity
In mathematics, a nonlinear system is one that does not satisfy the superposition principle, or one whose output is not directly proportional to its input; a linear system fulfills these conditions. In other words, a nonlinear system is any problem where the variable to be solved for cannot be...
circuits
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
or mathematics.
While some synthesis methods achieve sonic complexity by using many oscillator
Electronic oscillator
An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. They are widely used in innumerable electronic devices...
s, distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
methods create a frequency spectrum
Frequency spectrum
The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain. The frequency spectrum can be generated via a Fourier transform of the signal, and the resulting values are usually presented as amplitude and phase, both plotted versus frequency.Any signal...
which has many more components than oscillators.
Jean-Claude Risset
Jean-Claude Risset
Jean-Claude Risset is a French composer, best known for his pioneering contributions to computer music. He is a former student of André Jolivet and former co-worker of Max Mathews at Bell Labs....
was one notable pioneer in the adoption of distortion methods.
Some distortion techniques are: FM synthesis, waveshaping synthesis, and discrete summation formulas.
FM synthesis
Frequency modulation synthesisFrequency modulation synthesis
A 220 Hz carrier tone modulated by a 440 Hz modulating tone with various choices of modulation index, β. The time domain signals are illustrated above, and the corresponding spectra are shown below ....
distorts the carrier frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
of an oscillator by modulating
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
it with another signal. The distortion can be controlled by means of an index
Index (mathematics)
The word index is used in variety of senses in mathematics.- General :* In perhaps the most frequent sense, an index is a number or other symbol that indicates the location of a variable in a list or array of numbers or other mathematical objects. This type of index is usually written as a...
.
The method known as phase distortion synthesis
Phase distortion synthesis
NOTE: any readers who are struggling to understand this text, here are links to the missing Figures A and B:NOTE: any readers who are struggling to understand this text, here are links to the missing Figures A and B:...
is similar to FM.
Waveshaping synthesis
WaveshapingWaveshaper
In electronic music a waveshaping is a type of distortion synthesis in which complex spectra are produced from simple tones by altering the shape of the waveforms.- Uses :...
synthesis changes an original waveform by responding to its amplitude
Amplitude
Amplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
in a non-linear fashion. It can generate a bandwidth-limited spectrum, and can be continuously controlled with an index.
The clipping
Clipping (audio)
Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability...
caused by overdriving an audio amplifier
Audio amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification,...
is a simple example of this method.
(This method should not be confused with wavetable synthesis
Wavetable synthesis
Wavetable synthesis is used in certain digital music synthesizers to implement a restricted form of real-time additive synthesis. The technique was first developed by Wolfgang Palm of PPG in the late 1970s and published in 1979, and has since been used as the primary synthesis method in...
, which creates sound from lists of numbers, most often representing one period or cycle per wave. However, wavetable synthesis is identical to the special case of waveshaping synthesis where the original waveform is a sawtooth wave
Sawtooth wave
The sawtooth wave is a kind of non-sinusoidal waveform. It is named a sawtooth based on its resemblance to the teeth on the blade of a saw....
.)
Discrete summation formulas
DSF synthesis refers to algorithmAlgorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
ic synthesis methods which use mathematical formulas to sum, or add together, many numbers to achieve a desired wave shape. This powerful method allows, for example,synthesizing a 3-formant voice in a manner similar to FM voice synthesis. DSF allows the synthesis of harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...
and inharmonic, band-limited or unlimited spectra, and can be controlled by an index. As Roads points out, by reducing digital synthesis of complex spectra to a few parameters, DSF can be much more economical.