Sound quality in general is very complex and quite subjective, but with that said, there are multiple factors that are part of sound quality and even small things like how much CPU the Core is using at any given moment can impact what you hear.
It is possible that a multitude of environmental factors can impact sound quality and it’s hard to say what exactly it is that you’re hearing, just a perceived difference or if there were actually any environmental changes that impacted it.
I would suggest that you review the following two posts from our CTO, as they provide a great background on how the environment can impact sound quality: