Sound is a pressure wave that is produced by vibrations. When an object vibrates, it will create an automatic disturbance in the medium in which it is directly adjacent to. This medium is often, but not restricted to, air. The adjacent medium then carries the disturbance (sound) in the form of pressure waves.
As the sound travels through the air, the air molecules themselves don’t move downstream with the actual sound wave. Rather than moving with the actual sound, the air molecules oscillate back and forth about their individual equilibrium positions. As the molecules move back and forth, they disturb adjacent molecules, creating a chain reaction that we refer to as sound waves.
The frequency, or rate at which the molecules move, of the sound wave is dependent on the frequency of the vibrating source. For example, a high frequency vibration at the source will produce a high frequency sound wave. The different sounds we hear is produced from some variation of this vibration.
We perceive volume, or how loud a sound, is by the amount of sound pressure produced by a sound source. Greater sound wave compression is associated with more powerful, and therefore louder, sounds.
The following video from MED-EL will further explain the nature of sound waves.
The scale of sound in which a healthy ear can hear is quite large. We measure sound pressure using pascals (Pa) and perceptible sounds alone can range anywhere from .00002 Pa to 20 Pa. There is a small problem with using pascals alone to measure sound. Just to represent the audible sound scale, one needs 2 million places to move from the softest audible sound to loudest. That is why it is far more productive to use decibels (dB) to measure sound. For example, on the decibel scale, the smallest audible sound (near silence) is 0 dB. A sound that is 10 times more powerful than near silence will be 10 dB. A sound 100 times more powerful will be 20 db, and 1000 times more powerful than near total silence will equate to 30 db.
Sound can be perceived in a variety of different ways. View the following video from MED-EL to hear more.