Understanding virtual voices

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Wwise SDK 2023.1.8

To maintain an optimal level of performance when many sounds are playing simultaneously, you can use virtual voices to ensure that sounds below a certain volume do not consume valuable processing power and memory. The sound engine queues these inaudible sounds in the virtual voice list but does not play them. Wwise continues to manage and monitor these sounds, but when they are in the virtual voice list, the sound engine doesn't process them and they don't use any of the hardware’s physical voices.

When you use virtual voices, sounds move back and forth between physical and virtual voices based on whether their volume levels are under threshold, or whether the playback limit is exceeded and sounds are allowed to be virtual (as described in Understanding playback limit and priority). When the volume crosses the threshold set in Wwise Authoring, the voices are added to the virtual voice list and sound processing stops. As volume levels increase, which happens when sounds move within the maximum distance radius, the sounds move from the virtual voice list to physical voices, and the sound engine processes them again.

You can choose between three different playback behaviors for sounds as they change from virtual to physical. Each behavior has its own performance characteristics:

Behavior	CPU cost	Memory cost
Play from beginning	Medium: Voices are not serviced when virtual. Some extra operations are performed when voices switch between virtual and physical.	Low: All internal processing buffers are flushed when virtual.
Play from elapsed time	High: Voices are serviced at each buffer when virtual. Some extra operations are performed when voices switch between virtual and physical.	Low: All internal processing buffers are flushed when virtual.
Resume	Low: Voices are not serviced when virtual. No operations occur when voices switch between virtual and physical.	High: All internal processing buffers are retained when virtual.

Streamed sounds don't use I/O bandwidth when they are virtual. When the selected behavior is Play from beginning or Play from elapsed time, the I/O buffer is flushed, which causes a delay before the sound is audible again when voices switch from virtual to physical.

See Optimizing Voices for more information about virtual voices from the sound designer's point of view.

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