Wwise Expander Plug-in Effect

The Wwise Expander plug-in effect increases the dynamic range of a signal by weakening any part of the input signal that is below a pre-defined threshold value. When the signal is soft and below the threshold, the Expander begins to reduce the signal's gain. When the signal is at or louder than the threshold value, no gain reduction is applied to the signal.

A ratio factor determines the extent of the dynamic expansion when the input is below the threshold. For example, a ratio of 4 means that for every 4 dB the input signal is below the threshold, only 1 dB will be observed in the output signal.

To provide smooth transitions between the areas of gain reduction and no gain reduction, you can specify times for the attack and release properties. The attack time is the time it takes for the gain to be reduced when the input is below threshold. The release time is the time it takes for the signal to return to the threshold level where gain reduction is no longer applied.

The Wwise Expander plug-in contains a series of properties, many of which can be edited in real-time and can be mapped to specific game parameters using RTPCs.

You can use the Expander plug-in to reduce unwanted background noise. For example, you may need to reduce a low sounding background noise such as a hiss, so that other sounds could be heard more clearly. In some cases you can remove sounds from the output signal almost completely by setting a high expander ratio (over 10:1). This high ratio is known as a noise gate as it closes the gate for sounds whose gain has been reduced to this extent.

	Caution
	Sounds with a DC offset may alter the results of the expander effect. Make sure to remove the DC offset before applying the Expander effect in Wwise. You can remove the DC offset before importing the audio file, or in Wwise when you convert the audio file.

Interface Element

Description

Name

The name of the effect instance.

Effect instances are a group of effect property settings. They can be one of two types: custom instances or ShareSets. Custom instances can be used by only one object, whereas ShareSets can be shared across several objects.

Effect

The type of effect.

Shared by (Used by)

A list of objects that currently subscribe to the selected ShareSet.

This field is called “Used by” when editing a custom instance of the effect.

Returns the effect property settings to their default values.

This option is only available when editing a custom instance of the effect.

Notes

Additional information about the effect.

Effect Settings

Threshold

Specifies the point below which the expander will begin to process the signal and apply gain reduction.

Default value:-30
Range: -96.3 to 0
Units: dB

Ratio

The representation of the amount of expansion that has been applied. A ratio of 2:1 indicates that the portion of the output level below the threshold will be further reduced by two times the value of the input. At a ratio of 10:1 and higher, you can create a noise gate.

Default value: 4 Range: 1 to 50

Attack

The time it takes for the gain to be reduced when the input is below threshold.

Default value: .1
Range: .001 to .5
Units: Seconds

Release

The time it takes for the signal to return to the threshold level where gain reduction is no longer applied.

Default value: .01
Range: .001 to .5
Units: Seconds

Output gain

The gain applied to the output level after the dynamic expansion.

Default value: 0
Range: -24 to 24
Units: dB

Process LFE

Determines whether the effect is processed in the LFE channel or not. When selected, the effect is processed in the LFE channel. When unselected, the LFE channel will be unaffected.

Channel link

Applies the same gain reduction to all channels. This is implemented by taking the RMS power in the signal of all channels. The threshold is set by scaling the power in dB for the number of channels that are linked.

If this option is not selected, no information is shared between channels, and the effect is applied on a per-channel basis.

	General remarks on Wwise dynamic processing plug-ins
There is no interpolation of ratio control (RTPC parameter) for Wwise Compressor, Wwise Expander, or Wwise Peak Limiter. Changing this parameter during playback may lead to signal discontinuities on very clean signals. Sounds with DC offset may alter results of compression/expansion because the sidechain detection algorithm will be offset considerably. DC offset should be removed prior to use in Wwise. The Compressor, Expander, and Peak limiter are non-linear audio processes. This means that order of processing is important. For example, results will be different if you apply gain before or after the effect. For the first audio buffers, the processing algorithms are said to be in non-steady state. Because the estimated signal power operated by the side chain has no knowledge of the past, its estimate of signal power may be erroneous for a short period of time (but only if the Compressor is already engaged at the start of the sound). A solution to this (if it's a problem at all) is to start the Compressor with a ratio of 1 and shortly after bring it to the desired value. If the Compressor applies some gain reduction and is suddenly bypassed, a signal discontinuity will be heard. A potential solution is to gradually bring the ratio to 1 prior to bypassing the effect.

General remarks on Wwise dynamic processing plug-ins

There is no interpolation of ratio control (RTPC parameter) for Wwise Compressor, Wwise Expander, or Wwise Peak Limiter. Changing this parameter during playback may lead to signal discontinuities on very clean signals.
Sounds with DC offset may alter results of compression/expansion because the sidechain detection algorithm will be offset considerably. DC offset should be removed prior to use in Wwise.
The Compressor, Expander, and Peak limiter are non-linear audio processes. This means that order of processing is important. For example, results will be different if you apply gain before or after the effect.
For the first audio buffers, the processing algorithms are said to be in non-steady state. Because the estimated signal power operated by the side chain has no knowledge of the past, its estimate of signal power may be erroneous for a short period of time (but only if the Compressor is already engaged at the start of the sound). A solution to this (if it's a problem at all) is to start the Compressor with a ratio of 1 and shortly after bring it to the desired value.
If the Compressor applies some gain reduction and is suddenly bypassed, a signal discontinuity will be heard. A potential solution is to gradually bring the ratio to 1 prior to bypassing the effect.

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