A bandpassing is an action of filtering out all but a specific range of frequencies.

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Maurice Rozenberg has written:

'Constant high Q bandpass filters' -- subject(s): Bandpass Electric filters, Electric filters, Bandpass

'A digitally programmable filter' -- subject(s): Digital filters (Mathematics), Digital techniques, Signal processing

A low bandpass filter and a separate high bandpass filter should give the results required. These are usually in the form of crossover networks commonly used in speaker design. For low frequencies an LRC network is used (inductor, resistor, capacitor) and in high frequencies a simple electrolytic bipolar capacitor can be used. In more elaborate systems these can be active circuits (powered) or passive circuits as I previously mentioned.

central freqency of narrow band pass filter is the measure of difference between upper and lower cut off freqency