Simple, it s the vibrating of any surface. We can hear it when it has frequencies of between 15,000 and 20,000 herts. A sound wave is the vibration of sound moving through the air.
Sound travels through all substances, even solid substances.
It's a very early recorder of sound and of course it has to do with sound if it records it. The way they hear is by sending off high-pitched sounds called ultrasounds. Yes, they all do, no matter what kind they are. It can behave like a wave sometimes and then like a particle at other times. It is emitted by electrons circling around the nucleus of an atom.