| 摘要 |
PROBLEM TO BE SOLVED: To reproduce the signal components of a level equal to quantization noise, etc., or a fine level smaller than it at the time of reducing the quantization noise or quantization distortion from a digitized audio signal (digital audio signal). SOLUTION: In the case that tonal components tends to attenuate and a assumed tonal component level is not higher than the prescribed threshold value level, an attenuation arithmetic circuit judges the tonal components to be fine and music components to be buried in quantization noise to make the tonal component assumed by a tonal component assuming part 5 effective. Then, data in a band equivalent to the assumed tonal component is made zero and prescribed band signals excepting for the tonal components are attenuated to give a reverse FET part 7, which inversely transforms it to a time axis waveform. In addition, an adding part 9 adds it with a waveform from a reverse FET part 8 and outputs the adding result to an output terminal 11.
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