One of the more challenging issues I have faced with using SL is getting consistent volume levels with our narration. The problem has become even more acute because we now routinely use 2 narrators (female and male) for most of our e-learning projects.
We use professional narrators who provide us with finished files that we insert into our SL slides. The files generally require very little editing.
However, in our latest project, I was finding that I had to increase the volume of the female narrator from 35 to 50% to match the volume of the male narrator. This is easy enough to do with the SL audio editor. However, it is very time consuming, the results are imprecise, and there is no consistency from slide to slide or module to module.
There had to be an easier way. I use Sound Forge 10 Pro, which is excellent for most of my needs. But it does not have any leveler effects. ( I discovered that "normalize" increases or decreases the volume of the whole file, and does not adjust the volumes of the different speakers). I downloaded and tried Audacity (which has a "leveler" effect) but that did not work either. (Looking on the Audacity forum indicated that others found it does not work). (Adobe Audition appears to have a leveler effect, but I have no idea of how well it works).
After searching the Internet for "volume levelers" I was able to find several programs designed for the broadcast industry that claimed they could do the job. One of these was Auphonic Leveler.
With Auphonic Leveler, you can create a free account to try the program. I uploaded one of my files, ran the Leveler, and previewed the results. I was amazed at how well it totally leveled out the volumes without any distortion. Not believing the results, I ran a second audio file ... same results.
I immediately purchased the program and ran all of my project audio files through it. The results was consistency of volume between the speakers, across the slides and across all the modules. As I was synchronizing my animations across the project slides, I did NOT EVER have to touch or adjust the volume!
I have no affiliation with this company. There are several other vendors offering similar audio leveling programs. My experience with Auphonic Leveler has been excellent results, easy to use and it is affordable. It is now an indispensable tool in my e-learning development toolbox.
Like many others, I benefit greatly from the information provided here. So hopefully making you aware of "volume levelers" will also help you make your e-learning sound even more professional.