Working with Sound

Overview
Required Files
Tutorial

Overview

Sound in Synthetic Environments adds greatly to the realism of a scene. It provides atmosphere and additional clues to navigation and usability. Sounds can be positioned in 3D space, associated with objects and triggered by user interaction.

Various sound file formats are used in Synthetic Environments. If a scene is intended to be viewed via the Web it is essential that filesize be kept to a minimum. In the case of digitally recorded sounds, filesize can be reduced by specifying a lower sampling rate, changing a stereo sample to mono and compressing the resulting file.

VRML supports the MIDI, WAV and MPEG1 Audio file formats. MIDI is primarily used for background (ambient) music with the advantage being its incredibly small filesize. The downside is that MIDI sounds less realistic as it is computer generated. WAV on the other hand is a digital recording of music or a sound effect and therefore more realistic but filesizes are larger depending on how it was created and compressed. MPEG1 is also a digital recording but most often used in VRML to syncronise movie playback with its own audio track.

The VRML Sound node can be positioned and oriented in 3D space and also has a shape which is specified by the values minFront, maxFront, minBack and maxBack.

Options also exist to start, stop, loop and adjust the pitch of a sound.

Required Files

Download and unzip the following files (using WinZip) into the relevant folders of your working directory.

models_lights.zip (51Kb)

This file contains:

camera_lights.wrl

battery_textured.wrl

memstick_textured.wrl

sounds.zip (16.2Kb)

This file contains:

camera_click.wav

prodigy-nogood.mid

Tutorial

Launch Cosmo Worlds and Open the file camera_lights.wrl
Firstly, ensure that sounds are going to be visible in the scene - View Menu > Show Special Objects > Show Sounds.
To add a new sound, click on the speaker icon In the Choose a sound window, double-click the sound camera_click.wav.
Click in the perspective window to drop the sound into the scene. Move the sound using the DynaBox so it sits in front and centre as shown.
In the Outline Editor name the sound shutterReleaseSound and adjust the properties as follows: minBack 200 minFront 200 maxBack 400 maxFront 400
Notice how, as you change the properties, the size and shape of the sound changes in the perspective window. Anyone within the yellow ellipse will hear the sound full-volume. The volume fades between the yellow and red ellipses and anyone beyond the red ellipse will hear nothing. You will be unable to preview this sound until it is "wired up" to a trigger later in the Complex Interactions tutorial.
Repeat the steps above to add the MIDI music prodigy-nogood.mid.
Name the new sound backgroundMusic and set the properties in the Outline Editor as shown. The AudioClip properties loop, startTime and stopTime work in conjuction to automatically start the music as soon as the scene loads and continue playing forever. Note: make sure you capitalise TRUE.
Save your work.
Preview in Cosmo Player.