

It only nakes sense to apply DRY principles when you find you keep having to copy paste the same code to muliple locations on your codebase, and its reasonably clear it will never diverge from eachother. In other words, apply as needed to maintain development velocity (and in turn stability).
If the noise is due to footsteps and shit like that, earplugs dont do anything. The low freqeuncy vibration just cuts right theough them (and your skull if its low enough)