| 摘要 |
PURPOSE:To simplify circuit constitution of the titled device by digitizing the extraction of a specified frequency component. CONSTITUTION:When a digital audio signal is applied to a digital filter circuit 16, only a digital audio signal of a specified frequency component is extracted in accordance with a filter coefficient which is set by a filter coefficient storing circuit 18. That is to say, the filter coefficient is used for setting an extraction frequency range, and when its value is changed, a frequency range to be extracted is changed. The filter coefficient storing circuit 18 reads out successively the filter coefficient like a time division by a timing signal which is applied from a controlling circuit 22 and applies it to the digital filter circuit 16. Therefore, the extraction frequency range of the digital filter circuit 16 is changed as time elapses, and in accordance with its change, a digital audio signal of a frequency component of plural channels is outputted like a time series, and applied to an amplitude level displaying circuit 20.
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