Since Flash 5, designers and developers have had the capability to dynamically manage sound files using ActionScript. With the introduction of Flash MX(6), ActionScript makes it possible to not only attach the sound resource to the Flash movie at runtime, but it can even load MP3 sounds from files external to the Flash movie. The Sound object opens the possibilities for interactive audio in Flash and allows you to change every sound parameter dynamically through code rather then the authoring evironment. In today’s post we’re going to look at how to access the Sound class’s properties and methods in order to create efficient sound loading and playback in a Flash movie.

Introduction to the Sound Class
In ActionScript, you use the Sound class to manage sound resources - wheter attaching a sound from the movie’s library, loading MP3s, checking the playback time, or setting the volume. A Sound object is actually comprised of four seperate elements that work together to create and control a sound resource in a Flash movie:

• A sound file imported into the movie’s Library.
• A sound file(MP3) that you load separately during runtime.
• A sound file attached to the object.
• A sound file attached to a particulater Timeline or MovieClip object. The movie clip acts as a container for the sound resource, and every management function is proxied through the movie clip by way of the Sound object that targets it.

Creating a New Sound Object
As with most ActionScript classes, Sound objects require a constructor to create a new instance of the class. To create a new Sound object, you need the following constructor.

var sndResource:Sound = new Sound(sndInstance_mc);

In the preceding line of code, sndResource is the name for the specific Sound object you are creating, and sndInstance_mc is the movie clip within which you want the sound resource stored.

To better understand, the following ActionScript represents a new Sound object named sndTrack1 that creates a holder for an actual sound (from the movie’s Library or from an external MP3 file) on a MovieClip named sndHolder_mc.

var sndTrack1:Sound = new Sound(sndHolder_mc);

One More Thing: Getting to Know Sound Resources and Timelines

Although not strictly neccessary, it is advisable to use one movie clip per sound You can store many sounds in one movie clip. However there can be drawbacks as we will see.

The MovieClip object reference is an optional argument for the Sound constructor. If you do leave the argument out, the Sound object stores the sound resource on the _level0 timeline (Level 0). The following code creates a Sound Object that targets _level0:

var sndTrack1:Sound = new Sound();

If you are controlling only one sound with ActionScript or if you are not using the action in a loaded SWF file, leaving out the MovieClip object reference might not cause any problems. However, if you start to create multiple Sound objects without unique MovieClip objects to contain the sounds, you will run into trouble. Here is an example of two Sound_level0 sound resources:

var sndTrack1:Sound = new Sound();
var sndTrack2:Sound = new Sound();

This structure does not allow each sound to be stored in its own container. As a result, if you try to control one Sound object, the other sound resources will respond in the same manner.An example would be, setting the volume of sndTrack1 will effectively set the volume of sndTrack2 as well. In order to maintain complete and independent control over each sound resource that is used by each Sound object, I suggest to always create a unique MovieClip object to hold each sound resource.

It is very useful to make new movie clips using the createEmptyMovieClip method to hold your Sound objects:

this.createEmptyMovieClip(”sndHolder1_mc”, this.getNextHighestDepth());
this.createEmptyMovieClip(”sndHolder2_mc”, this.getNextHighestDepth());
var sndTrack1:Sound = new Sound(sndHolder1_mc);
var sndTrack2:Sound = new Sound(sndHolder2_mc);