A Wisconsin man armed himself with a handgun, convinced the banging and bumps he heard in his house were a sign that someone was breaking in. A woman who heard similar sounds rounded up her children and called 911.
Police in Janesville said they've been getting a number of calls about odd noises from frightened residents whose homes are contracting in the cold weather.
Temperatures in much of Wisconsin have been below zero this week after an unusually warm weekend with highs in the 40s.
Janesville police responded to 11 calls about suspicious activity as temperatures fell from Sunday afternoon into Monday, Sgt. Brian Vaughn said.
"People said they thought someone was breaking in or pounding on their walls or doors," Vaughn said. He added, "Nothing turned out to be wrong. There were no attempted break-ins. It was just strange house noises."
Eric Richards, who has a construction firm in Janesville, said many of the noises people hear in their homes are nothing to worry about, even if they sound odd.
"When you get temperatures dropping as fast as they did, you get a contraction that results in movement - a lot of pushing and pulling and snapping in the house," he said. "It can be very loud and very strange sounding."
A home's walls are exposed to the cold outside and warmer inside temperatures at the same time. That causes some parts to expand, while others contract, shifting doors, windows and other components. The movement causes the snapping, popping and banging that have been so alarming to residents.
Richards said that while homeowners shouldn't be unduly alarmed, they should pay attention to the noises because some can signal breaking pipes.
"That's something people need to be concerned about" because of the potential for water damage, he said.