I guess that's better than just making noise

Betsy had a friend over yesterday. At one point, the noise level from the living room was suddenly cranked up. Stomping, or banging or ... something.

Me (calling from the kitchen): What are you guys doing out there?

[Sudden, guilty silence.]

Betsy (quietly): Ummm ... We're making impact tremors.

Me: Oh. Okay. Carry on.