Before & After Clap Test A clap test uses a short, sharp sound to expose how sound moves inside a room. In any enclosed space, sound reflects off surfaces and overlaps with itself. Those reflections are always there, but they’re not always obvious when listening to music or speech. A short, sharp sound like a hand clap makes those reflections easier to notice, which is why it’s often used as a quick demonstration of room acoustics. In a studio environment, this makes it easier to notice how much