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Intel Spatial Audio for Java* Package Tutorial
Lesson 4: Understanding the Sound Model
| In this applet, the listener is attached to
the mouse. As you move the mouse closer to the
sound source in the center of the applet, you
should hear it closer to you. The inner, red
ellipse represents the ambient region while the
outer, black ellipse represents the limits of
audibility of the sound source. Click the buttons
to see how the model applies to a point,
directional, or ambient sound. You can edit the HTML file to specify a different sound file or different icons to represent the listener and sound source. Here is the source for the applet SoundModel. |
Goal: This lesson describes the details of the sound model which determines the range and directionality of a sound source, and demonstrates how the model can be used to represent different types of sounds.
Understanding the Dual Elliptical Model
The model describes a sound source in terms of two ellipses (ellipsoids in three dimensions). The inner ellipse outlines an ambient region of maximal intensity; this represents the physical area occupied by the sound source itself. The outer ellipse represents the limits of audibility of the sound source. Outside this ellipse, the sound is inaudible. Between the two ellipses, the sound attenuates with distance and may be further localized.
The inner ellipse is defined by the minimum front and back ranges; the outer ellipse is defined by the maximum front and back ranges. The "front" and "back" are determined by the sound direction.
This model can be applied to different types of sound sources. A point sound emanates equally in all directions from its source; this is the type of sound we've been using so far in this tutorial. In this case, the maximum front range equals the maximum back range and the minimum front range equals the minimum back range. A directional sound, such as the one in the image above, emanates primarily in one direction. In this case, the front values exceed the back values; the greater the difference, the more highly directional the sound. Finally, an ambient sound is one with a large inner ellipse. This applies to the case where the sound comes from a large area, such as the sound of many frogs croaking in a pond.
Use the SoundSource.setModel() method to set the sound model. You must pass an instance of the SoundSourceModel class, in which you specify the minimum and maximum front and back ranges for the sound, as well as its intensity. The intensity variable scales the volume of the sound; 1.0 is the natural intensity of the sound source.
The sound model works in conjunction with the sound orientation (the "front" direction) to determine the intensity of the sound at a given location.
This code sets the model and orientation for a sound source:
soundSourceModel = new SoundSourceModel(50.0f, 15.0f, 200.0f, 60.0f, 1.0f); soundSource.setModel(soundSourceModel); soundSource.setOrientation(1.0f, 0.0f, 0.0f);
This page was last updated on Feb 11th, 1997.
