Working with LFOs

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Working with LFOs

LFOs (Low Frequency Oscillator) are used to create modulation of property values over time. The properties of the LFO are:

Interface Element	Description
Depth	The amplitude variation of the oscillator. Maximum amplitude is 1.0. Default value: 100 Range: 0 to 100 Units: %
Frequency	The number of cycles per second. Default value: 1 Range: 0 to 20000 Units: Hz
Waveform	The shape of the modulator, from among the following options: Sine Triangle Square Saw up Saw down Random: Selecting Random will randomly apply a level each time the modulator runs. Default value: Sine
Smoothing	Low-pass filter over the waveform to smooth hard edges. This parameter can reduce output gain depending on your configuration. For a square waveform with an LFO of 1 Hz, gain reduction can be observed with a smoothing value as low as 30%. The higher the LFO frequency, the lower the smoothing value for which gain reduction is observed (for example, 2 Hz = 25%, 4 Hz = 20%, 8 Hz = 10%). For triangular or sawtooth waveforms, gain reduction can be observed with a smoothing value as low as 10%. Default value: 0 Range: 0 to 100 Units: %
PWM	The width of the pulse wave; only applies to the Square waveform. Default value: 50 Range: 0 to 100 Units: %
Attack	The time it takes for the oscillator to reach full amplitude. Default value: 0 Range: 0 to 100000 Units: s
Initial Phase Offset	The initial phase of the oscillator waveform. Default value: 0 Range: -180 to 180 Units: °
Scope	Define how LFO instances are created: Voice: An instance of LFO is created for every sound/object playback. Note/Event: An instance of LFO is created for every playing instance, or note when used in MIDI context. Game Object: An instance of LFO is created for each game object. Global: A single LFO is created for the whole project. Default value: Note or Event

In Wwise, some properties are additive (such as Voice Volume and Voice Pitch), and some are exclusive. When adding an LFO on the additive properties, the LFO modulation is added to the current value of the property. When adding an LFO on the exclusive properties, the LFO modulation replaces the current value of the property.

To modulate the Voice Volume with an LFO:

In the Project Explorer, select an object to add LFO.
In the Property Editor, go to the RTPC tab.
In the RTPC list, click the [>>] button.
From the selector menu, select Voice Volume.
Click the X-axis selector button.
From the selector menu, select LFO > Default (Custom).
Click the […] button to edit the LFO properties.
Edit the curve to set the range of modulation.

LFO objects can be created as Custom or ShareSet. Custom objects are stored in-place, directly inside the object that has it. ShareSets are stored in a separate work-unit and can be re-used across objects.

	Caution
	LFO and Envelope modulators' processing time depends on their RTPC usage. For most properties, a modulator is evaluated once per audio control frame. However, for the property Voice Volume, these modulators are evaluated at every audio sample frame. Use them selectively because they can consume a significant amount of a platform's memory and CPU.

	Note
	The RTPC cursors for LFO and Envelope modulators do not tell you their specific values at any point in time since they are determined by the modulator's internal properties.

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