sampling in bit-rate
By kyle Hofberg
Audio bit depth
In digital audio, bit depth describes the number of bits of information recorded for each sample. Bit depth directly corresponds to the resolution of each sample in a set of digital audio data. Common examples of bit depth include CD quality audio, which is recorded at 16 bits, and DVD-Audio, which can support up to 24-bit audio.
4-bit resolution with four levels of quantization
If this was 8-bit or any higher then the quantization would be more frequent resulting in a better sound quality.