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A Bitcrusher is a lo-fi (low fidelity) digital audio effect, which produces a distortion by the reduction of the resolution or bandwidth of digital audio data. The resulting quantization noise may produce a “warmer” sound impression, or a harsh one, depending on the amount of reduction.
A typical bitcrusher uses two methods to reduce audio fidelity: sample rate reduction and resolution reduction.
Sample rate reduction
Digital audio is composed of a rapid series of numeric samples that encode the changing volume of an audio waveform. To accurately represent a smooth waveform, digital audio requires a large number of samples at a high sample rate. The higher the rate, the more accurate the waveform. Higher sample rates also allow higher frequencies to be accurately encoded. DAWs today typically use 44.1 kHz or higher sample rates. Early digital gear used much lower sample rates to conserve memory for stored audio. A Speak & Spell from the 1970s, for instance, used a 10kHz sample rate.
Sample rate reduction (also called downsampling) intentionally reduces the sample rate to degrade the quality of the audio. As the sample rate is reduced, waveforms become more coarse and high frequencies are lost. At extreme reductions, the waveform becomes metallic sounding.
Samples in digital audio are recorded as integers or floating-point (real) numbers stored in computer memory. Those numbers are encoded using a series of on and off memory bits. The larger the number of bits, the more accurately a sample encodes the instantaneous volume level of a sampled audio waveform. DAWs today typically use 32-bit floating-point numbers. Early digital audio gear and video games used 8-bit integer samples or less. Roland's classic TR-909 drum machine used 6-bit integer samples.
Resolution reduction intentionally reduces the number of bits used for audio samples. As the bit depth goes down, waveforms become more stair-stepped and subtle volume variations are lost. At extreme bit reduction, waveforms are reduced to clicks as a waveform jumps abruptly from low to high and back again without intervening values.
Bitcrusher effects usually have at least two controls. One reduces the sample rate, while the other reduces the resolution.
The knob or slider for resolution reduction (a.k.a. "bit depth", "depth", or "bits") usually adjusts from 32 bits down to 1 bit.
The control for sample rate reduction (a.k.a. "downsampling" or "averaging") is sometimes shown in Hz for a new sample rate, or as a reduction factor. Sample rate reduction is sometimes shown instead as the number of consecutive samples to average together to create a new sample. A value of 20 reduces the sample rate to 1/20th of its original rate.
- An example of a sound distorted by a bitcrusher is in the introduction to the song “Chemicals” from the album "Shrink" by The Notwist.
- The samples used in the Roland TR-909 drum machine, for example, have a resolution of 6 bits, leading to a similar sound.
- In the musical genre Hardstyle, bitcrushing has become an essential effect in many tracks.
- In harder versions of the electronic music genre Dubstep/Drumstep, bitcrusher "yah yah" and "yoi yoi" effects have become more popular in the recent years of the genre with some artists using the effect more than the genre's signature "bass wobbles".
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