A digital audio device achieves bit-transparency if it passes digital audio data without affecting the data in any way. This device may be hardware, software, or a combination of both.
Testing for Bit Transparency
To determine if a device is bit-transparent, it can be tested by sending a pseudo-random bit sequence through it and monitoring the digital output. We typically generate the pseudo-random sequence using an Audio Precision digital signal generator. The Audio Precision includes a digital analyzer that is programmed to detect the pseudo-random sequence produced by the generator. The analyzer detects any differences between the generated sequence and the received sequence. The number of differences is tallied by a counter. A digital channel that is bit transparent will show no differences between the transmitted and received pseudo-random sequences.
EXAMPLE OF A SUCCESSFUL BIT-TRANSPARENT TEST:
11100011100011 -> Device -> 11100011100011
EXAMPLE OF A FAILED BIT-TRANSPARENT TEST:
11100011100011 -> Device -> 11100011100010
A device would fail a bit-tranparency test if it converts the sample-rate of the audio, shortens or lengthens the word-length, applies gain changes, applies eq or any other DSP or plug-in, or any other type of data manipulation.
Dither is a type of intentional variation (noise) which is added to a digital audio signal to avoid distortion caused by quantization errors.
Dithering in audio
Dither is often used when an analog signal is being quantized into a finite number of digital levels. It is also often used when a digital signal is being quantized into a fewer number of bits per sample corresponding to a fewer number of digital levels.