Audio in PowerPoint falls into four categories:  1) sound effects; 2) background music tracks; 3) audio you record using a microphone--either individual recordings on various slides, or a narration of your entire presentation; and 4) pre-recorded audio from files.  The first two types of audio are trivial, mostly overused, and intuitive enough so that there is no need to deal with them here.  The third type I will save for another time.  I will deal with the fourth type--pre-recorded audio from digital files--today.

PowerPoint 2007 supports various digital audio file formats:

• Apple audio interchange file format (file extensions aiff, aif, aifc)
• Unix environment sound files (au, snd)
• Microsoft WAV files (an audio file container for various codecs, wav)
• Microsoft Windows media audio format (compressed wma files)
• Standard mpeg-1 audio layer 3 (mp3, m3u)
• Musical instrument digital interface (midi, mid)
• CD Audio (cda, these files can only be played back from a CD-ROM drive)

These last two are music file formats, and will be ignored for our current discussion.  Ogg Vorbis and Flac files are two popular open source audio formats not supported by PowerPoint.

There are basically three ways to trigger a pre-recorded audio file in PowerPoint.  It is important to understand which file formats can be supported by which techniques.

1.  The first technique is to insert a sound from file.  This technique supports any of the sound formats listed above.  Do the following:

• On the Insert tab click the drop-down beneath “Sound” and choose “Sound from File…”

• Browse to find the sound file you want to insert, and click Insert after you have selected it from the Insert Sound dialog box. A playback choice dialog box will appear:

• If you will be presenting live, you almost always want to pick "When Clicked," because usually you will want to make some introductory remarks before playing the audio file.  If you plan to save for the web, you may want to pick "Automatically."  Otherwise you will need to include instructions to your viewers on how to start the audio playing.

Whether you click "Automatically" or "When Clicked," a speaker icon will appear on the slide.

This is a reminder to you that an audio file (or files--you can place as many as you want on a slide).  If you have chosen "When Clicked" it is also the trigger object for the audio.  When the speaker icon is clicked the audio will begin to play.

If you set up an audio file to play automatically (or when clicked) and then change your mind and want to set it the other way, click the speaker icon and then click on the “Sound Tools” tab that will appear. Change its Play Sound trigger in the Sound Options group on the ribbon.

By the way, if you have chosen for the audio file to begin playing "Automatically," and do not want the speaker icon to appear on the slide, you can drag it off the slide when editing in PowerPoint so that it will not appear.  The audio will still play.

2.  If you want your audio file to be triggered by clicking an object, but do not want the speaker icon to appear on your slide, you can use any object (graphic, drawing object, SmartArt, text--anything object) as the trigger.  However, this technique only works with wav files.  To use any object as your audio trigger:

• Select the object you want to use.
• Click on the Action button on the Insert tab.

• On the Mouse Click tab place a check in the Play sound box.
• Click the Play sound drop-down and select “Other Sound…”

• Navigate to the wav file you wish to associate with the object (either the graphic or text) and select it.

If you have chosen to use a graphic, bear in mind that you will need to provide some instructions, like “Click the picture to play the audio file.”

This technique has the advantage of being a little more sophisticated than the first technique, but has the serious disadvantage of supporting only the wav file format.  Since wav files are uncompressed, they tend to be very large, and will bloat the size of your presentation.  wma or mp3 files are far better choices if file size is a consideration.

3.  The third technique is to hyperlink to the file.  This will work with any media file tyope, as long as there is a media player associated with it.  The disadvantage (if this is one) is that the media player must appear on screen while the audio is playing.  It can, of course, be minimized and continue to play.  Here is how to hyperlink to an audio file.

• Select the object you wish to act as the action trigger (it can even be text that says "Click here to play the audio).
• Click on the Insert tab and the Action button.

• On the Mouse Click tab select the “Hyperlink to:” radio button.
• Click the drop-down and select “Other File…”
• Navigate to the King speech—this time using the wma file—and select it.

Using this approach may result in a security warning from PowerPoint, if it has been kept up to date. It certainly will with Windows Vista.

Clicking “Yes” will cause the media player to appear and the clip to play.

To avoid this security warning, you may want to link to a streaming media file that exists apart from your PowerPoint presentation. This assumes reliable access to the web.

This last technique has the advantage of supporting any file format, even formats not natively supported by PowerPoint, like the QuickTime mov or Real media formats.  The disadvantages are that you must be sure there is a properly configured media player available on the computer from which you will be presenting; you must be sure it has the codecs required to play your media; and the media player must appear on screen, unless you have taken steps to prevent this.

Regardless of the trigger technique, once you have placed an audio file on a slide, you can control its properties from the Sound Options group of the Sound Tools tab.  (The Sound Tools tab will appear in PowerPoint 2007 when an object that has a sound file associated with it is selected).

Notice the "Max Sound File Size" control in this group.  This refers to wav files only, and has no effect on other file formats.  It means that wav files less than 100KB will be embedded in the presentation file (the pptx file).  Those above 100KB will be linked.  You can change this parameter to cause larger files to be embedded (or smaller ones linked) but you will be bloating the size of your final pptx file if you make it larger.

The number one difficulty people have in presenting with media files is that they fail to play during the presentation.  This is usually because they have been linked--not embedded--in the presentation and when the presenter copied the presentation file to portable media, like a CD or flash drive, they failed to copy the linked media files.  The best advice for overcoming this problem is to create your presentation in the same folder where all your media files are stored, and then copy the entire folder over to your portable media.

The number two problem with presenting with multimedia is that the media fails to play on a computer supplied in the room where the presentation is given.  There can be many reasons for this.  The best thing to do is to rehearse beforehand using the actual equipment in the actual room.  If this is not possible, take your own equipment--as far as possible, so you can be sure you have everything you need to give a successful presentation.