SPEECH ENCODING METHOD AND APPARATUS, INPUT SIGNAL DISCRIMINATING METHOD, SPEECH DECODING METHOD AND APPARATUS AND PROGRAM FURNISHING MEDIUM

In a speech codec, the total number of transmitted bits is reduced to decrease the average amount of bit transmission by imparting a relatively large number of bits to the voiced speech having a crucial meaning in a speech interval and by sequentially decreasing the number of bits allocated to the unvoiced sound and to the background noise. To this end, such a system is provided which includes an rms calculating unit 2 for calculating a root means square value (effective value) of a filtered input speech signal supplied at an input terminal 1, a steady-state level calculating unit 3 for calculating the steady-state level of the effective value from the rms value, a divider 4 for dividing the output rms value of the rms calculating unit 2 by an output min_rms of the steady-state level calculating unit 3 to determine a quotient rmsg and a fuzzy inference unit 9 for outputting a decision flag decflag from a logarithmic amplitude difference wdif from a logarithmic amplitude difference calculating unit 8.