Table of Contents

Wwise SoundSeed Air - Woosh

SoundSeed Air consists of two separate plug-ins: SoundSeed Wind and SoundSeed Woosh. The SoundSeed Woosh plug-in is a source plug-in that generates sounds as an object passes through the air. To create these types of sounds, the characteristics of the deflector object are defined, along with the trajectory movement and speed of the object. No source audio files are necessary as the woosh sounds are completely synthesized. SoundSeed Woosh allows you to save memory in your game because you no longer need the .wav files that you would have traditionally used. Additionally, the Woosh source can be used to create variations using the multiple randomization features.

[Note] Note

If you plan to develop, integrate, and distribute SoundSeed Air with your game, you need to purchase a separate license. For more information, contact the Audiokinetic sales team at: sales@audiokinetic.com.

The SoundSeed Woosh scene differs from the SoundSeed Wind scene in that it consists of a trajectory or path that describes the motion of the object through the scene. The traveling object is made up of one or more groups of deflector objects. Each group that is created has its own set of properties, including frequency and gain. Adding deflector sections to a group can help to divide up the different areas of the wind deflecting object. If you have more than one section, Wwise interpolates the property settings between sections from the property settings of one deflector to another. This can be useful if the shape of your object changes from one end to the other, like a traffic cone.

Object Path

The actual woosh sound is created by the speed of the traveling object as it effects the resonating frequencies of the different groups of deflector objects. By modifying the number of deflector groups, the number of deflectors within a group, their resonating frequency properties, and the speed at which the object is traveling through the air, you can create a wide variety of woosh sounds in your game.

The following illustration demonstrates a typical woosh scene where the trajectory of the traveling object, in this case a sword, has been defined. The resonating frequencies of each deflector along with the speed at which the object is traveling through the air will determine the actual woosh sound. The object travels along the path based on the Woosh speed curve.

In Woosh, the relationship between time, path, and speed differs slightly from other path/time relationships in Wwise. In Wwise, objects that use 3D User-defined positioning move at the same speed through the entire path; this is not necessarily the case in Woosh. If an automation curve is used to define the speed of the traveling object, it will move at speeds defined by this curve; covering a longer distance along the path when the speed is at its highest point. The position reference point, which is available in both the Object Path graph and the Property graph view allows you to cross-reference the speed of the traveling woosh objects at specific points along the path.

Using Automation Curves

The speed of the object as well as the various deflector properties can be controlled over time using automation curves. You can create sophisticated curves by adding any number of points and using a variety of curve shapes. The following illustration shows an example of a sophisticated object speed automation curve.

[Note] Note

To maintain a reasonable level of performance, the object speed curve is limited to using linear curve shapes between points. All other automation curves can use the full range of curve shapes available in Wwise.

Cyclic Nature of Automation Curves

When woosh sounds are looped, the automation curves are repeated in a cyclical manner. When using very short durations, you may experience the phenomenon where, at increasing playback rates, the sound appears to speed up and slow down. This occurs because the space between each sample becomes larger than the actual automation curve. When this occurs, the next control sample will be taken from a different point at the beginning of the next cycle of the automation curve.

Control Rate Oversampling

In the case of highly dynamic sounds, you can oversample the control rate for all curves to ensure that the sound's characteristics evolve in a way that's close to the control curves. Oversampling causes control curves and path data to be read at a higher rate than the regular buffer period, which is approximately 21 ms on most platforms. The oversampling value effectively brings the control rate down by the control's value. For example, a control rate oversampling of 16 will result in the sampling of control curves to occur every 1.33 ms (~21 ms/16). This diminishes resonant frequency discontinuities and ensures that the positioning of the object matches the path more closely than with less frequent reading. It is important to note that there is a computational cost to oversampling and is best used only when needed.

The following illustration demonstrates how oversampling can be used to affect the control rate in an effort to better represent the actual control curve.

Spatialization

The SoundSeed Woosh plug-in uses angle-based spatialization with a minimal amount of spread. This means that if an object is placed fully to the right of the listener, it will only be passed through the right channel. If, on the other hand, it is placed in the upper right corner (45 degrees from the listener) it will be passed through both the left and right channels, but with substantially more power through the right channel. In contrast to axis-based panning, this method achieves a high level of positional dynamics when the object is placed near the listener.

In a four-channel configuration, objects placed in a corner will be passed mostly through the channel that corresponds to their location but will also pass through each adjacent channel with half the power of the main one.

Distance-Based Attenuation

You can also apply distance-based attenuation to the woosh sound. Basically, a -6 dB attenuation is applied each time the object's distance is doubled after the Minimum distance. You can fine-tune the distance-based attenuation as the object travels along its trajectory by specifying values for the following properties:

  • Minimum distance - The distance from the center of the scene, in all directions, where no attenuation gain is applied.

  • Roll-off factor - The slope of the attenuation curve, where higher values produce steeper slopes or faster attenuation. For example, a roll-off of 2 attenuates the woosh sound twice as fast.

The following illustration demonstrates the attenuation model used by the SoundSeed Air plug-ins. Three different roll-off factors are used with the same min distance to show how the attenuation gain is applied in each case.

The main advantage of using the positioning and attenuation controls in the Woosh plug-in is that you can define the speed at which a wooshing object will travel along its path using an automation curve. You also have the option to oversample the control curves, which allows you to better match the object's position along its path at all times.

You can still use the general Wwise controls for attenuation and positioning, but you must understand that these controls act independently from the positioning and attenuation controls within the plug-in. If you choose to use either of the general Wwise positioning or attenuation controls, a position must be defined for the object that contains the Woosh source. You can do this by creating a path in 3D User-defined positioning or by attaching the object that contains the Woosh source to a game object using 3D Game-defined positioning.

Color Noise and Spectral Tilt

You can also specify the spectral tilt of the synthesized woosh sound by choosing from a variety of different noise colors, including:

  • White noise - Produces no spectral tilt.

  • Pink noise - Produces a -3 dB per octave spectral tilt, resulting in a signal less emphasis on the higher frequencies.

  • Red noise - Produces a -6 dB per octave spectral tilt, resulting in a signal that places even less emphasis than pink noise on the higher frequencies.

  • Purple noise - Produces a +6 dB per octave tilt, resulting in a signal that places emphasis on the higher frequencies.

The following illustration demonstrates the spectral tilt of the various noise colors:

Controlling Properties Using RTPCs

In Wwise, most properties can be modified in real time using the property sliders. Many of the properties can also be mapped to parameters in your game using RTPCs. A special indicator is placed beside the property value showing whether it uses an RTPC or not.

The following table describes the two types of RTPC indicators:

Indicator

Name

Description

RTPC - On

A property value that is tied to an in-game parameter value using RTPCs.

RTPC - Off

A property value is not tied to an in-game parameter value.