TBH I'm not sure that will fix it... I have Dolby set ON in my -HDR and have no issues with sound on any of the 3 TVs I've connected to it whether SD, HD 5.1 or 2.0.
As I understand it, during hdmi handshake the two devices are supposed to 'agree' on what format to send the audio and pictures.
However I have and occasionally still do have 'oddities' during handshake (or lack of handshake) with the Foxsat-HDR. The latest one is if I turn on to watch the pvr when it is recording (or in the 15 min before recording), when I don't get sound but I do get the picture. I need to switch the my GT60 to another source and back to cure it.
This is one of a number of 'foibles' we have due to the less-than-perfect hdmi implementation by Humax. If this is the problem you have then this is the simplest way to fix it.
{With my previous TV there was no picture or sound in the same circumstance, but the fix was the same.}