Aetherial De-Esser overview¶

The Aetherial De-Esser is a client-side processor available in both TX and RX instances. It reduces harsh sibilance ("S" and "T" sounds) by monitoring a narrow frequency band and ducking it when the signal level in that band exceeds a set threshold.

Before you start¶

The de-esser is available as a standalone docked applet (TX only, labeled "Aetherial De-Esser") and through the Aetherial Audio Channel Strip (RX and TX).
The docked applet is hidden until the De-Ess stage is enabled. Enable it via the CHAIN widget inside the Aetherial Audio (TXDSP) parent container.
To open the RX instance, use the Aetherial Audio Channel Strip icon for the receive channel, then click the De-Ess stage. The panel opens with the title "Aetherial De-Esser — RX".
No radio connection is required to configure the de-esser.

How it works¶

The de-esser uses a sidechain design. A bandpass filter isolates the sibilance band defined by Freq and Q. When the level in that band exceeds the Thresh value, the de-esser attenuates the band by up to the Amount value. The rest of your audio passes through unaffected.

The panel displays two live indicators while audio is active:

Sidechain response curve — shows the bandpass filter shape with a ball marker at the current centre frequency. As you adjust Freq and Q, the curve and ball update immediately. Frequency axis labels (100, 500, 1k, 2k, 4k, 8k, 12k) are rendered using cached text for performance.
Gain-reduction bar — a horizontal soft-red strip that fills from the right to show how much attenuation is being applied at any moment. The scale runs from 0 to 24 dB; a tick marks the −6 dB point. The meter refreshes approximately 30 times per second.

When the de-esser stage is bypassed, the entire panel renders at reduced opacity (approximately 55%) to give a clear visual indication that the stage is inactive. To bypass or re-enable the de-esser, use the single-click gesture on the DESS stage in the CHAIN widget.

TX and RX instances¶

The de-esser has separate instances for transmit and receive:

Instance	How to access	Title bar label
TX (docked applet)	Click the De-Esser icon in the Applet Panel	"Aetherial De-Esser"
TX (channel strip)	Open the TX channel strip, click De-Ess stage	"Aetherial De-Esser — TX"
RX (channel strip)	Open the RX channel strip, click De-Ess stage	"Aetherial De-Esser — RX"

Each instance maintains independent settings for Freq, Q, Thresh, Amount, Attack, Release, and Slope. The docked applet omits Attack and Release knobs.

What each control does¶

Control	Default	Valid range	Setting key (TX)	Behavior
Freq	6000 Hz	1000 – 12000 Hz	`ClientDeEssTxFrequencyHz`	Logarithmic mapping. Sets the centre frequency of the sibilance band.
Q	2.00	0.5 – 5.0	`ClientDeEssTxQ`	Linear mapping. Sets the bandwidth of the sibilance band — higher Q = narrower.
Thresh	−30.0 dB	−60.0 to 0.0 dB	`ClientDeEssTxThresholdDb`	Linear mapping. Level above which the de-esser starts attenuating the band.
Amount	−6.0 dB	−24.0 to 0.0 dB	`ClientDeEssTxAmountDb`	Linear mapping. Maximum attenuation applied at peak sibilance. Values are negative (or zero) because they represent reduction.
Attack	1.0 ms	0.1 to 30.0 ms	`ClientDeEssTxAttackMs`	Exponential mapping. Sets how quickly the de-esser responds once sibilance crosses the threshold. Present in the Channel Strip StripDeEssPanel (RX and TX). The docked ClientDeEssApplet omits this knob.
Release	100 ms	10.0 to 500.0 ms	`ClientDeEssTxReleaseMs`	Exponential mapping. Sets how quickly gain returns after sibilance drops below the threshold. Present in the Channel Strip StripDeEssPanel (RX and TX). The docked ClientDeEssApplet omits this knob.
Slope	24 dB/oct (2 stages)	12 / 24 / 36 / 48 dB/oct (1 to 4 stages)	`ClientDeEssTxSlopeStages`	Cycles the sidechain bandpass cascade count. Each stage adds 12 dB/oct of rolloff outside the sibilant band. Higher slope = narrower effective notch, less mid-band collateral on Ess-heavy phrases. Present in the floating StripDeEssPanel (left column, bottom). Label shows 'N dB/oct'.

Inline value editing¶

Each knob supports inline value editing. Click the displayed value text to open a small text entry field. Type a new value and press Enter or click outside the field to commit. The value is automatically clamped to the knob's valid range. Press Escape to cancel the edit and revert to the previous value. This feature works the same way in the docked applet and the channel strip panels.

Slope button¶

The Slope button in the Channel Strip panel lets you adjust the sidechain filter steepness:

Click the button to cycle through 12 → 24 → 36 → 48 dB/oct (1 to 4 cascaded bandpass biquads).
Each click increases the rolloff by 12 dB/oct outside the sibilant band.
Higher slope values create a narrower notch around the centre frequency, reducing collateral attenuation of mid-range speech.
The button label updates to show the current setting (e.g., "24 dB/oct").
The sidechain response curve updates to reflect the new slope.
Slope setting persists independently for TX and RX paths.

Settings persistence¶

Each instance saves and restores its control values from the settings database:

Setting key	Purpose
`ClientDeEssTxFrequencyHz`	TX centre frequency
`ClientDeEssTxQ`	TX bandwidth factor
`ClientDeEssTxThresholdDb`	TX sidechain threshold
`ClientDeEssTxAmountDb`	TX maximum attenuation
`ClientDeEssTxAttackMs`	TX attack time
`ClientDeEssTxReleaseMs`	TX release time
`ClientDeEssTxSlopeStages`	TX slope stage count
`ClientDeEssTxEnabled`	TX enabled state

RX settings use a parallel key set (ClientDeEssRx*). Settings are saved when you adjust any knob or close the panel.

Theming¶

The de-esser panel and its knobs use the application theme system. Knob colors (background ring, foreground arc, pointer handle, label text, value text) are drawn from theme color keys:

color.knob.background — knob background ring
color.knob.foreground — knob value arc
color.knob.handle — knob pointer line
color.text.secondary — knob label text
color.text.primary — knob value text

The sidechain response curve also uses theme colors:

color.background.0 — curve widget background
color.background.1 — grid lines and major grid lines
color.text.label — axis labels
color.accent.danger — sibilant band curve (soft red)
color.accent.dim — threshold/marker lines
color.accent.warning — centre-frequency ball glow
color.text.primary — centre-frequency ball core

The docked applet container is registered with the theme as applet/deess, allowing per-applet color overrides when defined by the active theme.

Tips¶

Start with Freq at the default 6.0 kHz and sweep it slowly while speaking sibilant words. Watch the gain-reduction bar — maximum deflection indicates you have found the peak sibilance frequency.
A Q of 2.00 is a reasonable starting point. Increase it to isolate a narrow problem band; decrease it if the sibilance is spread across a wider range.
Set Thresh so the gain-reduction bar only moves on genuine "S" and "T" sounds, not on normal vowels or consonants.
The −6 dB tick on the gain-reduction bar marks the default Amount value. Keeping reduction near that tick usually produces transparent results. Larger amounts are available but can make the effect audible as pumping or lisping.
Use the Slope button to fine-tune the filter steepness. Start with 24 dB/oct and increase if you hear too much mid-range attenuation on sibilant-heavy phrases.
Use different settings for TX and RX — you may need more aggressive de-essing on receive than on transmit, or vice versa.
When the stage is bypassed, the panel dims noticeably. If the panel appears dim and you are not hearing de-essing, check that the DESS stage is not bypassed in the CHAIN widget.