How is this different from a gate?

A gate makes a decision per moment and produces silence below its threshold, which is why it needs hysteresis and a hold time to avoid chattering. An expander scales instead, so a quiet passage stays audible but further down, and the result keeps its texture rather than being cut into.

Will it remove the background noise completely?

No, and that is deliberate. Expansion divides the quiet material down by a ratio, so a floor thirty decibels below the signal can be pushed to sixty, which is enough to stop it being noticed without deleting it. Complete removal needs a gate or a spectral tool.

How do I set the threshold?

Just above the noise floor of the recording. If you can hear the noise sitting under the speech and the threshold is set below it, nothing will happen; if consonants start disappearing, the threshold has climbed into the quiet parts of the signal and should come back down.

Why is the maximum downward ratio only one to ten?

Because beyond that an expander stops being an expander and starts behaving like a gate with a soft edge, inheriting the gate's artefacts without its controls. When you want that much reduction, the gate is the honest tool for it.

What does the release time change here?

How quickly the gain comes back up after the signal rises above the threshold again. Too fast and the noise floor swells back audibly after each phrase; too slow and the beginning of the next passage sounds dull because the gain has not recovered yet.

Audio Expander

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Audio Expander pushes everything below a threshold further down, which is the opposite motion to a compressor. It tightens a noisy recording gradually rather than cutting to silence.

What is Audio Expander?

Set the threshold, ratio and timing, drop a file, and process. The report gives the threshold, the downward ratio, and the average level before and after.

The controls:

A threshold from sixty decibels below full scale down to twelve below, defaulting to minus thirty five.
A downward ratio from one to ten to one to one to one and a tenth, defaulting to one to two, shown as the downward figure.
A knee from zero to twelve decibels, defaulting to six.
An attack from one to fifty milliseconds, defaulting to five.
A release from twenty to six hundred milliseconds, defaulting to a hundred and fifty.

The motion is the mirror image of compression. Everything above the threshold passes through unchanged, and everything below it is reduced in proportion to how far below it sits, according to the ratio: at one to two downward, a passage ten decibels below the threshold comes out twenty decibels below. That proportionality is what distinguishes expansion from gating. A gate decides yes or no for each moment and produces silence, while an expander keeps the quieter material present, just further down, so the result reads as a recording with more contrast rather than one with holes in it. The knee again spreads the transition into the reduction so the change is not abrupt at the line, and attack and release decide how quickly the gain follows. The practical use is setting the threshold just above the noise floor of a room recording. Speech and music sit above it and are untouched; hiss, air conditioning and room tone sit below it and sink, and because they sink rather than vanish the result keeps its natural texture. On a signal that already has a clean floor, an expander will do very little, which is the correct outcome rather than a failure. Too low a threshold and nothing is affected; too high and the quiet consonants of speech start to be pushed down, which is usually heard first as a loss of intelligibility rather than as noise reduction.

What it does not do:

It reduces rather than removes, so a very loud noise floor still leaves something behind.
High ratios begin to behave like a gate and share the gate's artefacts instead of the expander's smoothness.
No frequency dependence, so broadband noise and quiet musical detail are treated identically.
The average level falls, and no make-up gain is applied automatically.
Channels are processed independently, so a stereo image can shift on very quiet material.
Output is sixteen bit WAV.

Use it when a recording needs tightening without hard edges: a noisy room that should stay natural, a drum bus where the gaps between hits should feel quieter, or a spoken take where the pauses should not sit as high as they do. When the quiet parts should become true silence, the gate does that with its own controls for holding open and fading the edges, and when the noise itself should be targeted by its character rather than its level, the noise reducer and the specialist removers work on what the noise sounds like. The motion it applies has a name worth knowing, since it is what separates the two tools people most often confuse: downward expansion scales the quiet material rather than switching it, so the result keeps the room's character instead of acquiring the abrupt edges a gate produces.

How to use Audio Expander

Drop an audio file onto the panel and play a quiet passage to hear its floor.
Set the threshold just above the noise floor so speech and music stay clear of it.
Choose a gentle downward ratio and check the knee and timing.
Press process, compare the reported average levels, and download the result.

When to use Audio Expander vs related tools

Audio Expander is the gentle way to add contrast and push a noise floor down without cutting holes in the material. Audio Gate removes rather than reduces, which is more decisive and more drastic. When the noise has a recognisable character, Noise Reducer and Hiss Remover address it by its spectrum instead of by its level.

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