BSS Audio DPR-404 Owner's Manual - Manual (Page 24)

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De-essing and Peak Limiter
A common problem encountered when amplifying or recording the human
voice is the large amount of high frequency energy heard as the sibilant (Sss)
sound. These sounds can reach levels considerably greater than the normal
voice level, and can result in signal break-up or distortion. It is possible to
control these sounds by using a compressor which is specially configured to
respond to, and only reduce, these high frequencies. Selective high frequency
compression is generally called de-essing, as it removes the high frequency
Sss content from the program. The DPR-404 de-essing circuitry is specially
configured to enable precise selection and control of high frequency
sibilance. The variable FREQ control tunes not only high pass filters in the
controlling side chain but also in the main subtracter so that gain reduction
will only affect the high frequencies, leaving the rest of the program
unprocessed.
In use, the frequency control is adjusted such that the filter is capturing the
correct high frequency sibilance, and the DE-ESS level control, working like a
threshold control, is used to set the correct degree of gain reduction. The
associated green LED indicates the start of de-essing action, whilst the red
LED indicates the maximum 10dB compression. The dynamic attack and
release settings are automatically adjusted by the circuitry depending on the
program type.
11.3 De-essing
Fig 12.1 Effect of
de-essing on output