It seems likely! Around here, people with septic systems put straw bales on them to trap snow and reduce freezing. Maybe talk to locals with similar systems, or call a service person for advice.

On a serious note the pump could be making that noise because it is having to work hard to pump. A likely reason is the pipes are building up with frozen matter. This usually happens on systems where the run to the tank is long but can happen on any. This year due to lack of snow and brutal cold a friends pipe froze solid. Is it a cause of concern for you? Maybe, given the brutal winter it is possible to be a rare occurrence. On my friends system we thawed the ground which unthawed the pipes and we dug the pipes up and ran heat tape along them incase it happens again.

Before you freak out remember I am speculating.

SCG

There is a pretty good chance that there was a small stone in it and it finally got flushed out. Every few years it is a good idea to get a septic truck to suck out the solids and check for the concrete in the tank breaking down. That is if it is concrete.

Slimy_Okra, do you know when the last time the system had been sucked out? Ours requires it every three years, other households more frequently, even yearly depending upon the number of bums in the house.

Thanks for the replies. I think it was sucked out a year ago. However this winter was really bad with the ground frost penetrating deep all over the region. It'll be interesting to see if this occurs again next week.