They absolutely do vary in intensity from time to time, which can be a relief, wouldn't want it to be all super bad all the time, right?
Maybe try ear plugs if you can. Dogs who bark just kill my head, ugh. I love dogs though, but can't handle the barking sometimes.
I know for sure things adjust and are worse, I have pin pointed why, however I do think when you're getting sick can be worse. Once I got dizzy for half a week and my dr said that could just be from some kind of virus or sinus infection making everything all dizzy while your body is fighting it off. At least now that I know that things can be better sometimes and worse other times, I can pay attention to myself and try to be nice to myself even though I am having a worse day with sensory issues and not try to force myself. There are often other days to handle things better. so it is good to know that.
hope you feel better. 
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Your Aspie score: 165 of 200
Your neurotypical (non-autistic) score: 48 of 200
EQ 12 SQ 70 = Extreme Systemizer