PURPOSE: To output the audio having naturality audibly, by measuring the short time average power of audio signal mixing surrounding noise and that for surrounding noise, subtracting the average power of surrounding noise from the average power of audio signal, and determining the amplitude of the excited power supply from the subtracted power.

CONSTITUTION: The audio signal from the audio signal source 205 including the noise from the noise sound source 206 is measured to measure the parameter including frequency spectrum and audio information, and the audio is synthesized from the parameter value. In such an audio analysis and synthesis unit, the input signal of the signal source 205 including noise and the noise source 206 is fed to the short time average power measuring units 211 and 215 provided with the analyser side 202, the short time average power is measured, and the measuement value of noise is subtracted from the measurement value of audio signal with the audio power 213 and it is fed to the coder 212. The output at the analyzer side 2 with this constitution is fed to the composite coder at the synthesis side 203 and the output of the composite coder 216 is fed as the exciting sound source information of the audio synthesis filter 223.