acoustic filter

The mass distribution and flex of the bridge, acting as a mechanical acoustic filter, have a prominent effect on the sound.

They are now "Pulse Filters", "Pulsation Filters", "Acoustic Filters for liquids".

The source-filter model of speech production models speech as a combination of a sound source, such as the vocal cords, and a linear acoustic filter, the vocal tract (and radiation characteristic).

However, since ACTS has been phased out of service in much of the United States, combined with the integration of acoustic filters into many payphone handsets, the practice of red boxing is rarely possible anymore.