And all of a sudden you could hear a big pop.

"Within a second I hear a pop," the driver is quoted as saying in a police report.

Students working elsewhere in the building reported hearing a small pop at the time.

You hear or feel a pop in your knee during an injury.

Suddenly, the security officer heard a pop, and realized one of the strangers had disappeared.

"She heard a pop and felt the pain in her leg," the sergeant said.

It was harder in the air, but then I heard a loud pop.

I heard a pop and thought it was the floor.

She heard a pop, felt a sudden, sharp pressure in her inner ears.

He heard a loud pop and stopped cold, unable to move his left leg.