Telecommunications signals are seldom linearly
encoded, but rather are companded [a combination of compression
& expansion]. This allows for a more uniform S/N ratio over
the entire range of signal sizes.
If the quantization step size is constant,
the S/N ratio decreases for small signals. To prevent this, the
step size varies according to the signal size.
The telecom industry has used logs to measure
acoustic and electrical signals. The most common is the dB unit.
North American µ-law and European A-law codecs
perform the same function but with a slight difference in implementation..