Two sources of sound are:
Vibrating objects: When an object vibrates, it creates a disturbance in the surrounding air molecules. This disturbance then propagates through the air as sound waves, which our ears can detect and interpret as sound.
Pressure variations: Rapid changes in pressure can also create sound waves. For example, when we speak, our vocal cords rapidly vibrate, causing changes in air pressure that propagate through the air as sound waves. Similarly, when a drum is struck, the air inside the drum rapidly expands and contracts, creating sound waves that we can hear.