VOICE COMPRESSION METHOD, VOICE EXPANSION METHOD AND VOICE COMPRESSION DEVICE

PROBLEM TO BE SOLVED: To provide a voice compression method, a voice expansion method and a voice compression device capable of reducing an operation amount. SOLUTION: The voice compression method is provided with a step (step S4) of comparing voice data and decoded voice data and obtaining code information indicating sizes of both, a step (step S5) of calculating a difference value of both, and a step (step S6) of dividing the entire range of values that the difference value can take into a plurality of groups, referring to a difference information table indicating relation of respective group numbers and the difference values included in the respective groups and acquiring the group number including the difference value as difference information. Then, data including the code information and the difference information are turned to the compressed voice data of the voice data.