De-esser
A Deesser , also: De-Esser , is an audio effects device or a corresponding software, e.g. B. VST plug-in, which allows the level of sibilants (sibilants) contained in a recording of speech or song to be automatically reduced.
Basics
If the human voice is recorded, it is often necessary, for aesthetic reasons, to subsequently amplify the high frequency components of the recording (around 7 kHz to 11 kHz) using an equalizer (equalization filter). This gives the voice a more robust sound and more presence, especially if it is a singing voice that has to assert itself over musical instruments in the sound image of a music recording. But even with pure voice recordings (radio speakers, radio plays, etc.), a voice has a more direct effect on most listeners and attracts more attention at the same volume. A problem arises when raising the high frequencies of a voice recording: Voiceless hissing sounds (s, ss, ß, sch, z, tz) consist almost exclusively of such frequencies and are reproduced disproportionately loud by amplifying these areas. This effect is also intensified by the compression of the speech signal, which is often used , since these sounds are perceived as loud, but are low in terms of technical signal level and are hardly reduced by the compressor. In this respect, a recording that has been edited in this way sounds very uncomfortable, as the sibilants are disproportionately loud and extremely intrusive.
function
A de-esser first separates the lower from the problematic middle and upper frequencies, and then compresses the latter, which automatically lowers the level of too loud sections. Then both signals are mixed together again. The result is a present and good-sounding recording of the human voice without intrusive sibilance.
It is interesting that some de-essers can be adjusted to male or female voices by simply pressing a button or clicking the mouse. The frequency spectrum of a female sibilance differs from that of a male. Since this does not always work, a De-Esser with differentiated setting options is preferable, e.g. B. the problematic frequency range.
If a de-esser is not available in the effects rack, you can put together a conventional compressor with a sidechain input and a conventional equalizer yourself. The output signal is looped through the equalizer into the sidechain input of the compressor. The settings on the equalizer make the frequencies of the sibilants available (increase from about 7 kHz, decrease the rest) and the decrease can be set on the compressor.
Problems
If the lowering is exaggerated, the sibilants can be completely filtered out. In the case of a singing voice, it can sound as if the singer is poking his or her tongue (lisping). The resulting effect can be used with individual voices in a choir. If there are several voices that differ in pitch and are sung at the same time, only the vocal sounds are relevant. S-sounds are almost at the same pitch and would be multiplied by overlapping, which is why the S-sounds can be completely filtered out for all choir voices, whereby the S-sounds of any voice must be retained. If you use the technology with individual components (equalizer and compressor with sidechain input), you can also filter the plosives (P, T ...) of the choir voices at the same time, which can disturb the homogeneous overall picture of a choir. For this purpose, the basses of the equalizer must also be increased to around 100 Hz. A mutual influence during the filtering is not to be expected under normal circumstances, since the sounds are temporally separated from each other.
See also
literature
- Roland Enders: The home recording manual. The way to optimal recordings 3rd, revised edition, revised by Andreas Schulz. Carstensen, Munich 2003, ISBN 3-910098-25-8 .
- Rolf Beckmann: Manual of PA technology. Basics, components, practice. 2nd Edition. Elektor-Verlag, Aachen 1990, ISBN 3-921608-66-X .