| 摘要 |
PROBLEM TO BE SOLVED: To suppress generation of abnormal sound during muting at a voice signal processor, which outputs a positive phase side PWM (pulse width modulation) signal and an opposite phase side PWM signal from an input digital voice signal. SOLUTION: Resolution of an input digital voice signal is converted into low resolution, and furthermore noise shaping processing is carried out to generate a positive phase side digital signal (REF_P) and an opposite phase side digital signal (REF_N). Patterns are compared for both signals during muting at buffers 20 and 22 and a pattern comparison portion 24. If both patterns coincide, selectors 26 and 28 output to PWM modulators 30 and 32 a setting value which serves as duty 50% for each digital signal, in order to optimize switching timing to 50% duty when muted. COPYRIGHT: (C)2009,JPO&INPIT
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