Using a band-pass filter method

Issue Time:2011-11-22

   Wide bandpass filters are used in many different applications including radios, home electronics projects and music production. A bandpass filter can be visualized as a rounded ridge placed on top of range of frequencies. The frequencies under the ridge will be allowed to pass, those outside of it will not. Since the essential concept is the same, using a bandpass filter for all of these applications is similar; it is all a matter of controlling the shape and positioning of the filter curve.

    Modify the pass band. This is the size of the filter curve. If it were infinitely large it would allow in the full range of frequencies; if it were infinitely small it would only allow a single frequency. On most audio and electronic equipment that utilize band pass filters this can be modified with a dial. The frequencies higher and lower wide bandpass filter than the pass band will not be allowed to pass through the filter.Modify the placement of the filter along the frequency scale. The frequency scale depends on what the filter is being used for. If the filter is being used for audio applications, the frequency scale will be 20-20,000 Hz, the range of human hearing.

    Modify the slope. The slope is the steepness of the ridge of the filter curve. Many bandpass filters will not cut off the ranges beyond the pass band completely, and not all filters will be able to control this slope. If the slope is wide, it will allow a wider range of frequencies that are outside of the pass wide bandpass filter , but at lower decibels than those frequencies within the pass band. The controller for this will be labeled as the slope -- it will not control the size or placement of the pass band, only its sharpness.