Bit Depth

Bit Depth refers to how much information is captured with a sample. Common settings in audio programs are 16 or 24 bits.

Please note that the description below using graph paper is only an illustration. It contains some simplifications. All sampled system contains filters on the output. In a correctly designed system this makes sure all sine waves below the Nyquist frequency are represented exactly, there are no errors introduced as can be implied from the sample rate pictures.

The bit depth for a correctly designed system in the same way only influences the noise level, not the exactness of the signal. The singnal after the output filters will never be stair shaped as in the illustration.

Each sample measures the amplitude (shape) of the wave, and higher bit depths allow the analog shape to be more closely matched. Imagine a piece of graph paper, on which you were trying to line up the graph with the smooth analog curve of a sine wave. The smaller the boxes on the graph (higher bit depth), the more closely you could match the shape of the sine wave.

In the diagrams below, the X axis represents sample rate (each line equals one sample) and the Y axis represents bit depth.

At a low bit depth, the shape of the wave cannot be matched very closely	At a low sample rate, the shape of the wave also cannot be matched very closely
At a higher sample rate and bit depth, the shape of the wave can be more closely matched.	However, the higher the frequency of the sound, the more difficult it is to closely match the wave.

Bit depth is exponential, so a 24-bit sample holds 256 times as much information as a 16-bit sample. A 16-bit sample has a range of 65,536 values, while a 24-bit sample has a range of 16,777,216.

See Also

• Sample Rate

• Digital Recording

Category: Technical