For me it’s the noise of conversations around me in an open office - I find it really hard to tune out. And being interrupted frequently when I’m focusing on something.
Oh, and hot desking (which I thankfully don’t have to do anymore but made me so anxious every day for years).
I could go on…!
I work in a huge care home... so for sure the constant alarms going off 
Yes I have loops earplugs which I wear as required. I get it with you saying about being interrupted from an activity though. Different situation but I have that at my work too and hate it when im super focused on something. Im required to do an awful lots of small talk obviously too with staff and residents which is struggle with lots on some days more than others depending how exhausted I already am 
