Noise and why we need it in a synthesizer.
This sounds odd on first hearing that we would actually want to introduce noise into an audio signal, after all most designers of amplifiers and effects pedals spend their time trying to reduce it as much as possible. If you have ever listened to an old short wave radio, a worn vinyl LP, or an FM radio with a weak signal that hissing you heard is noise.
Noise in an electronic circuit is created by random voltages, or variations in voltage introduced to a greater or lesser extent by all electronic components. It’s even present in digital audio systems to some degree.
But consider trying to synthesize certain sounds such as a snare drum, a cymbal, or the sound of wind and rain. All of these sounds and instruments are based around noise of one sort or another. It can also be used to introduce randomly changing control voltages.
More about noise.
There are various types of noise, referred to by colour to describe the frequency spectrum. The two we are concerned with are:
White Noise: This has an even distribution of “energy” or signal level over the entire audible frequency range.
Pink noise: This has a greater concentration of energy, or signal level in the lower audible frequency range.
Creating Noise.
All we need is the Oscillator module set to White or Pink noise, it needs no other settings or controls.
Third Party noise module.
Elena Novaretti has also produce her own bespoke module the ED Noise Gen 2, which saves using an Oscillator to generate noise. It can also be conveniently turned off via the Power plug when not required.
Elena’s Help file supplied with the module is shown below:
ED NOISE GEN (1 and 2)
Simple lightweight white/pink noise generator to be used in place of the stock SE oscillator, when only a noise source is needed.
Please note that the noise sequences generated for a given seed are always identical (i.e. the module does not rely on any external parameter other than the seed you can supply, e.g. from system time and so on)
PIN DESCRIPTION
Type (List) – noise type:
a) White (flat spectrum) or
b) Pink (richer in the low spectrum end)
On/Off (Bool)- the module can be completely switched off when not in use
Retrig (Bool v2 only) – resets the pseudorandom sequence corresponding to a given Seed integer.
Seed (Integer) – a long integer used as the random seed
Output (Audio-Volts) – output audio signal
Important note about polyphony
The fact this module may or may not be cloned, in polyphonic usage may have audible implications, depending on the specific usage.
As with any generator or oscillator, when this module is placed inside a polyphonic circuit it will NOT be cloned, unless any MIDI-CV 2 plugs are connected to its inputs.
With Noise Gen V1: there are really no input plugs which one may want to connect either directly or indirectly to the MIDI-CV 2.
With Noise Gen V2: users may want to drive the Retrig pin with the Gate line from the MID CV 2, to generate identical noise sequences at every key press: in this case the module WILL be cloned, even if the Gate line were interrupted with a switch (this trick can be used to have the module always cloned even when no retriggering is required).
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