Description Many communications systems are primarily concerned with the speaking voice.
Intelligibility is more important than high-fidelity sound quality.
In fact, such extraneous signal content could be distracting and interfere with the intelligibility or audibility of the desired voice signal. Such low or high frequencies are effectively noise as far as this application is concerned. All frequency components below 300Hz or above 3000Hz can be safely ignored with no loss in the communicated information. This is a natural application for a band-pass filter. The schematic diagram for a practical speech filter circuit is shown, and a parts list for this project is given.