Where can I find free "Murdoch Mysteries, S07E with decent audio (wherever I found it, the sound was a bumping hiss)?

Get Netflix. Streaming or disc, the sound has been fine. Check your connection or service provider. Many TV's have crappy speakers in them and weak audio amplifiers that go bad quickly, so taking sound from streaming media players or cable boxes to outboard speakers or HiFi gives best audio.

Check your local TV listings, some channels show it in the early mornings.