When it comes to adding narration audio (voice-overs), Captivate developers have plenty of choices. You can insert audio using any of the following methods:
Right-click any slide object and choose Audio > Import to or Audio > Record to. If you choose Import to, you will be presented with an Import Audio dialog box. You can import wav's or mp3's.
Object-level audio is ideal if you want to quickly add sound effects to slide objects. However, I wouldn't use this technique for voiceover audio. If you attach audio to multiple slide objects, there is a good chance that those objects will take longer to work with (when compared with a project that has more slides, but fewer objects per slide). There's also a Section 508/compliance issue you'll need to forward-think, but I'll cover that later.
To add Background audio, choose Audio > Import to Background or Audio > Record to Background. Once again, you will either be presented with a dialog box to open an existing audio clip, or a dialog box where you can record your own audio. You will also have options to lower the background audio if there is competing audio on the slide, and you can elect to loop the background audio. There is even an option to stop the audio when users close the lesson.
Background-level audio is perfect for background music... if you intend to include it. Personally, I think background music will quickly becomes a distraction (perhaps even an irritant) for your learners, which is why I shy away from it.
As for voiceover audio, I don't recommend that you add it to a project as the background. If you do, you'll likely find yourself facing all kinds of object-to-audio synchronization issues as you move from slide to slide within the project.
You can attach audio directly to the slide by selecting the slide on the Filmstrip and choosing Audio > Record orAudio > Import.
There are a couple of reasons that slide-level audio is preferred over object-level or background-level audio. First, there's a production speed benefit. When I produce eLearning lessons for my customers, I try to keep the number of slide objects to a minimum. Typically I only allow for one text caption, and one button or click box per any given slide. Keeping the number of slide objects to a minimum speeds up the production process significantly In fact, fewer slide objects means less time spent synchronizing the timing of those objects with other objects or voiceover audio.
If you're not concerned with saving production time, perhaps my second reason for adding voiceover audio at the slide level will get your attention. If you are required to include closed captions in your eLearning (for Section 508 compliance), you must include voiceover audio. In fact, closed captions cannot be added to slide objects. You can only insert closed captions at the slide-level, and only if the slide already contains audio
Over the years I've heard horror stories from developers who were required to add closed captions, but couldn't because the audio had been added to slide objects instead of the slide itself. Unfortunately, the only solution to the dilemma is to remove the object audio, and then manually add the audio to the slide. It's not a difficult process, but it takes time. Of course, now that you've read the text above, that particular production conundrum isn't something you'll need to worry about.