The linked page shows instruction on how to modify the sound on a command-line basis;
as the problem has been resolved by that means before, according to the page information.
One of the suggestions from that page mentions: "You could also use the built-in afconvert program.
There's a guide here macworld.com/article/1138554/105audioterm.html – rpt1 Dec 22 '15 at 15:03"
While there may be some other pre-made software or file, one would have to look to Olympus
or a later version (as of yet, not available) of OS X, if there is sufficient demand for the software
for a maker to resolve the problem at the level of an easy fix download. If Olympus were to fix it
there could be something such as a firmware update for their camera product so it could create
files able to work correctly in Mac OS X.
There may be an application that modifies QuickTime player to use it to hear/see video.
I've not experienced the issue, as my two cameras aren't set to use audio; & I only capture stills.
Good luck & happy computing! 🙂