Audio is an extremely efficient way to deliver information. Consider a training video on measuring and weighing chemical compounds. Which track audio or video would be the most important in conveying information? In the sound track a narrator explains the procedure, and in the video track someone is measuring and weighing compounds. Which track would you remove if necessary? Which could stand alone? The audio track. Consider enhancing your presentation with an audio component. Audio can be captured and optimized fairly easily, and it compresses well.
When recording original audio, take the time to do it right. Low-frequency background noises, such as the hum of a ventilation system, will be inseparable from your audio track; no amount of tweaking will eliminate it altogether. Remember, too, that the downsampling and compression you will have to perform to make your audio Web deliverable will emphasize any flaws in your recording.