(See the Wwise Expander Properties below.)
The Wwise Expander 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.
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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. |
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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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Using Wwise Expander on an Audio Objects Bus
Applying a linear Effect, such as the Wwise Parametric EQ, to
multiple Audio Objects independently is identical to applying it once to a downmix of those
objects. Typically, this is not the case with non-linear Effects, such as compression or expansion.
However, the Wwise Expander plug-in is a special type of Effect, called an Object Processor.
When the Wwise Expander plug-in is inserted on an Audio Objects bus, the result is as follows:
The Effect is instantiated only once per bus instance, regardless of how many Audio
Objects are routed to the bus.
It achieves the expansion of multiple Audio Objects together by working on an
internal downmix, all while preserving the individual Audio Objects (that is, without
mixing them down).
The gain reduction is common to all Audio Objects.
Expansion is implicitly occurring in Channel Linked mode. Consequently, the
Channel Link option is ignored.
Refer to Using Effects with Audio Objects for further details.
Wwise Expander Properties
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