PURPOSE: To allow a communication in the good communication quality state without generating a sense of incompatibility for the communication in the background noise state.

CONSTITUTION: This high-efficiency voice coding system by the A-b-S method is provided with a prescribed number of noise code tables 2 storing the noise code vectors in response to the frequency characteristics of the input sound signal, a selecting means 4 connected to the outputs of the noise code tables 2, and an analyzing means 6 analyzing the, frequency characteristics of input noises and switching the selecting means 4 in response to the analyzed frequency characteristics. The output of the selecting means 4 is used as the noise code table 2 used for coding the input voice.