To improve the acoustic feeling and the tone quality by detecting narrow bandwidth noises and switching the noise eliminating characteristics.
An adder 28 performs the noise eliminating process in which estimated background noise signals are subtracted from output signals X(f) of an FFT computing element 4 and processed signals E4(f) are transmitted to a narrow bandwidth noise discriminating section 29. A frequency axis voice detector 31 provides a maximum power level at a signal X(f) and its frequency to the section 29. Then, the section 29 obtains the signal value at the maximum power level frequency for a K-th frame and then, obtains the deviation between the maximum power level and the obtained value. If the deviation is larger than a threshold value, the section 29 discriminates that they are background noises having narrow bandwidth noises ('there exist narrow bandwidth noises'). If the deviation is less than the threshold value, it is discriminated as voices. Then, the noise eliminating characteristics in the output signals from the device are varied in accordance with the discrimination result of the section 29.
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