The rotation of a wheel can be expressed as the simultaneous simple harmonic motion in both the x and y direction of every part of the rim of the wheel. At the end of one revolution every point has returned to its starting point. The rotation is therefore periodic and repeats itself rotation after rotation. Measured in seconds. Measured in cycles per second or Hz.
All periodic vibrations produce waves in the medium in which they are located.
Since vibration is so common in nature, it is no surprise that waves are extremely common in nature. We therefore need to understand a few things about the nature of the wave phenomena if we are to study nature in any sort of detail. A typical example would be a radar gun used by speed cops. The origin of sound waves is any material object that is emersed in air and is undergoing some high speed vibration. The speed of sound depends on the pressure, temperature and density of the air in which it propagates.