Is it the abominable snowman? A burglar? It's the basic laws of physics, according to Norbert Delatte, civil and environmental engineering department chairman and professor at Cleveland State University.
"Pretty much all building materials – wood, concrete, steel – expand with heat and contract with cold," Delatte said. "The foundation of a house stays at a more normal temperature where the outside of the house is trying to shrink against it, so whatever connections there are between the foundation and home, they would be making some noise."
Sound travels further through the cold, dense air and the lack of activity overnight make the noises sound louder then they would during the day, he said.
According to Jim Dill, general manager at Cleveland Repair Co., the concrete foundation "footers" on houses are constantly shifting depending on the temperature and moisture in the ground.
In extreme cases, the ground freezes, cracks and shakes slightly — what's known as acryoseism, or "frost quake." Toronto and parts of Ontario reportedly experienced one Monday night.
Nails can contract and slip in wooden homes, creating a "pinging" sound, said Joseph Prahl, professor of mechanical engineering and aerospace at Case Western Reserve University.
Wooden floors can also be louder in the cold, according to Steve Gesis, executive director of sales at The Cleveland Restoration Group, which manages 600 residential homes throughout the area.
"When everything contracts, flooring will become a little tighter, and when you walk on it you will really hear those sounds," Gesis said.
Gesis said the wooden deck attached to the back of his home sounded like gunfire Monday night, what could be a result of joints and nails shifting as they contrast against one another.
In most cases, these noises indicate minor movements that do not typically cause damage, but popping noises can also be the cause of a bursting pipe, a problem many homeowners were experiencing Tuesday.
'Pop' goes the pipe
Tony DiNardo, operations manager at the Plumbing Source, said the 90 reports of frozen pipes the company received Tuesday were the most he's seen in a single day in his 27 years as a plumber.
If ice clogs the pipes long enough, they'll explode. Or more commonly, block water access to a portion of the house.
"Once the lines are frozen, they expand a little bit. I've had people tell me they hear a popping sound then notice water coming through a ceiling or a wall," DiNardo said.
In many cases, he said people could have prevented significant water damage, but didn't know where the valve switches were located.
DiNardo advises people to keep faucets trickling, so water continues to move, preventing freezing. However, water froze around three of his customers' outdoor drains Tuesday from the constant trickling, clogged the pipes and caused sewage backup to come through faucets, toilets, showers and other water sources.
Gesis said the situation is exacerbated in vacant homes where no one is there to report a broken pipe. He said Cleveland Restoration crews visited several of the vacant homes it owns to find severe water damage.
"In one home there was a burst pipe in the center of the basement and it was spewing water in every direction. There was nearly eight inches of standing water and in that case you will have to cut out all the drywall and insulation," Gesis said.
That process can take weeks and up to $25,000, he said.
With temperatures projected to reach 20 degrees Wednesday, and 45 by the weekend, expect even more creaks and pops as houses expand and pipes thaw, Delatte said.
"This weekend we are expecting to see more water damage as the ice melts and water starts to run again," Dill said.