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<meta name="description" content="Tom's Audio Processing plugins for
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audio engineering on the Linux platform.">
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<meta name="keywords" content="TAP-plugins TAP Reverb Editor
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Reverberator Equalizer EQ Vibrato Tremolo Echo Tom Szilagyi LADSPA
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JACK Plugin Linux Audio">
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<meta name="author" content="Tom Szilagyi">
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<font size="+2" color=#004060><b>TAP</b>-plugins</font><br>
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<font color=#004060>Tom's Audio Processing plugins</font><br>
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<font size="-1" color=#004060><i>for audio engineering on the Linux
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<a href="../index.html">[ Home ]</a>
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<a href="../ladspa.html">[ LADSPA plugins ]</a>
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<a href="../reverbed.html">[ TAP Reverb Editor ]</a>
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<a href="releases.html">[ Releases ]</a>
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<a href="cvs.html">[ CVS ]</a>
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<a href="general.html">[ General Info ]</a>
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<a href="manuals.html">[ Plugin Manuals ]</a>
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<a href="autopan.html">[ TAP AutoPanner ]</a>
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<a href="chorusflanger.html">[ TAP Chorus/Flanger ]</a>
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<a href="deesser.html">[ TAP DeEsser ]</a>
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<a href="dynamics.html">[ TAP Dynamics (Mono & Stereo) ]</a>
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<a href="eq.html">[ TAP Equalizer and TAP Equalizer/BW ]</a>
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<a href="doubler.html">[ TAP Fractal Doubler ]</a>
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<a href="pinknoise.html">[ TAP Pink/Fractal Noise ]</a>
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<a href="pitch.html">[ TAP Pitch Shifter ]</a>
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<a href="reflector.html">[ TAP Reflector ]</a>
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<a href="reverb.html">[ TAP Reverberator ]</a>
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<a href="rotspeak.html">[ TAP Rotary Speaker ]</a>
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<a href="limiter.html">[ TAP Scaling Limiter ]</a>
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<a href="sigmoid.html">[ TAP Sigmoid Booster ]</a>
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<a href="echo.html">[ TAP Stereo Echo ]</a>
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<a href="tremolo.html">[ TAP Tremolo ]</a>
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<a href="tubewarmth.html">[ TAP TubeWarmth ]</a>
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<a href="vibrato.html">[ TAP Vibrato ]</a>
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<img src="tap_deesser.png" alt="[TAP DeEsser GUI as shown in Ardour]">
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<b>TAP DeEsser</b> is a plugin for attenuating higher pitched
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frequencies in vocals such as those found in 'ess', 'shh' and 'chh'
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sounds. Almost any vocal recording will contain 'ess' sounds, whether
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a strong vocal delivery, from bad recording, speech impediments or
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simply many 'ess' words spoken together. Wind instruments and other
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musical instruments can also create shrill high-pitched noises. Audio
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engineers need to control these harsh 'ess' sounds in most recordings.
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<h3>General information</h3>
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<table cellspacing="0" cellpadding="5" border="1">
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<tr><th align="left">Unique ID</th><td>2147</td>
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<tr><th align="left">I/O ports</th><td>1 input / 1 output</td>
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<tr><th align="left">CPU usage (44.1 kHz)</th><td>5.9%</td>
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<tr><th align="left">CPU usage (96 kHz)</th><td>12.8%</td>
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<tr><th align="left">Hard RT Capable</th><td>No (see Notes)</td></tr>
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<tr><th align="left">In-place operation</th><td>Supported</td>
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<tr><th align="left">run_adding() function</th><td>Provided</td>
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Audio input is fed into the audio path and the so-called Sidechain. In
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the Sidechain, the signal is filtered and then an attenuation value is
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computed based on the filter output. This computation is done using a
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hard-knee compressor characteristic with a threshold level set by the
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"Threshold" control and a compression ratio of 1:2. The compressor
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attack/release time is 10 ms for instant operation.
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The filter applied to the Sidechain signal has two modes of operation:
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Highpass and Bandpass. Highpass mode is useful for attenuating several
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different 'ess' sounds. Bandpass mode is more suitable for attenuating
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a specific high frequency. The chosen filter's frequency is set by the
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General advice about setting the "Frequency" control: The sounds
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attenuated by this plugin can be fit into four categories: male 'ess',
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male 'ssh', female 'ess' and female 'ssh' sounds. 'Shh' settings are
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quite applicable for 'ch', 'th', and hard consonants, such as 't',
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'd', and 'k' as well. The following table lists frequencies for these
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four types of sounds. Note that these are only provided as a starting
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point for your own experimentations, as the characteristic frequencies
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of individual vocalists can vary in a suprisingly wide range. Use your
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<h3>Recommended frequency values</h3>
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<table cellspacing="0" cellpadding="5" border="1">
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<tr><td>Male 'ess'</td><td>4500 Hz</td></tr>
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<tr><td>Male 'ssh'</td><td>3400 Hz</td></tr>
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<tr><td>Female 'ess'</td><td>6800 Hz</td></tr>
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<tr><td>Female 'ssh'</td><td>5100 Hz</td></tr>
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Generally, female 'ess' and 'shh' sounds vary more in frequency than
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those of males. Due to this situation, you may find that using the
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Sidechain filter in the Highpass mode may be more responsive.
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Otherwise, with the Sidechain filter in Bandpass mode, only a narrow
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frequency area is being responded to. So if a singer has esses with
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varying frequency, try the Highpass mode of the Sidechain.
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When choosing between Sidechain modes (e.g. Highpass or Bandpass) and
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setting the "Frequency" it may be very helpful to hear the Sidechain
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signal, which controls the compression of the through-passing audio:
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this is why the Monitor control is provided. While listening to the
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Sidechain signal, try to set the controls so that almost everything
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you want attenuated can be well heard, and even more importantly,
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almost everything you want to keep intact doesn't show up in the
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Another aid in setting the plugin is the "Attenuation" output meter:
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this shows the momentary attenuation applied to the signal. It
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shouldn't show a significant attenuation all the time. Instead, it
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should indicate that attenuation springs into action only
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<h3>Summary of user controls</h3>
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<table cellspacing="0" cellpadding="5" border="1">
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<tr><th>name</th><th>min. value</th><th>default value</th><th>max. value</th></tr>
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<tr align="center"><td>Threshold Level [dB]</td>
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<tr align="center"><td>Frequency [Hz]</td>
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<tr align="center"><td>Sidechain Filter</td>
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<td>Bandpass</td></tr>
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<tr align="center"><td>Monitor</td>
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<td>Sidechain</td></tr>
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Setting the "Threshold" too low will result in an unpleasant muffled
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sound. Also, if the singer starts sounding as if she had suddenly lost
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her teeth, take this as a sure sign that your "Threshold" setting is
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way too low. Use the ever popular Bypass button and watch out for side
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This plugin is best on vocal tracks, although it can be applied to
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mixed tracks as well. However, you should expect an increased amount
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of side effects (especially muffling and pumping of the sound) when
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attempting to de-ess the vocals of a mixed track.
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Internal variables that depend on user settings are re-computed only
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when the corresponding user settings are changed. This keeps the
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plugin from being hard RT capable, although the effect of this
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occassional re-computation is not really noticeable when looking at
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Because the Sidechain processing algorithm involves converting from
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linear to decibel values for every sample, a custom, very fast lin2db
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function was implemented via a log10 table, which is computed and
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stored when the plugin library is loaded by the host. Without this
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hack (that is, calling <code>log10f()</code> for every sample), CPU
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usage would be almost exactly twice this much.
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$Id: deesser.html,v 1.3 2004/08/17 13:05:16 tszilagyi Exp $
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doc/ladspa/deesser.html
