Presence filter
A presence filter (from the Latin praesens = present) is in the recording studio technology frequently used filter assembly for the uplift of certain frequency bands , in particular in the region of the maximum ear sensitivity of 1000 to 5000 Hz. Depending on the selected frequency is produced a bell-shaped frequency response , similar to a resonance curve .
The formant areas of the sounds of musical instruments or human speech are raised by a presence filter , so that e.g. B. a solo instrument is removed from the acoustic background. In this way, the intelligibility of human speech can also be significantly improved.
To set a presence filter you need:
- the center frequency f 0
- the gain ( amplification factor ) in dB for setting the maximum increase (up to 15 dB)
- the bandwidth B per octave or the quality factor Q = f 0 / B for setting the narrow bandwidth or edge steepness; the lower the bandwidth and the higher the quality factor (with constant center frequency and constant gain factor), the narrower the filter or the steeper its edges.
The individual starting points for increasing the desired frequency can usually be selected in small dB steps.
literature
- Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 3rd part, communications electronics. 5th edition, Verlag Europa-Lehrmittel, Wuppertal, 1980, ISBN 3-8085-3225-4
- Karl Hermann Huber: Filtering and sifting of audio frequencies. 1st edition, Frech Verlag, Stuttgart, 1974, ISBN 3-7724-0162-7