Digital Audio
Quantisation is the process of converting the continuous amplitude of an analogue audio signal into a series of discrete numerical values during digital conversion. It determines the resolution of the digital signal and directly affects noise and dynamic range.
Quantisation occurs during the analogue-to-digital conversion process, when each sampled amplitude of the analogue waveform is rounded to the nearest available digital value. The number of available values is defined by the system’s bit depth, for example, 16-bit audio provides 65,536 possible levels, while 24-bit provides over 16 million.
Because quantisation can only approximate the true analogue value, it introduces a small, random error known as quantisation noise. This noise forms the lower limit of a system’s dynamic range and manifests as a very low-level background hiss. The higher the bit depth, the finer the resolution and the lower the quantisation noise.
Quantisation error is statistically randomised by a process called dithering, which adds a small amount of controlled noise before conversion. This prevents distortion and makes the quantisation noise less correlated with the signal, producing smoother low-level performance.
In practical terms, quantisation defines how accurately an analogue waveform is represented in digital form. It is a core principle of PCM (Pulse Code Modulation) and underpins the clarity, resolution, and dynamic range of every digital recording system, from early digital tape machines to modern 32-bit floating-point DAWs.
