All sounds are caused by a vibrating object, that is. an object that is moving back and forth rapidly. These vibrations cause molecules in the air to and make the molecules next to them move, and soon there is a movement back and forth of the molecules in the air that produces what we call “sound waves”.
But the vibrations differ from each other and they produce different kinds of sounds. There are three basic differences between one sound and another. The differences are in loudness, pitch, and tonal quality.
Loudness of a sound depends both on the distance of the vibrating object from your ear and on the distance the vibrating body moves its to-and-fro motion. The greater this movement is, the louder the sound will be.
The highness or lowness of a sound is its pitch. This depends upon the speed of vibration (the frequency) of the sounding object. The tonal quality depends upon the number and strength of the “overtones” which are present in the sound. This happens when there are higher sounds at the same as lower ones, and they blend.
We cannot hear until a sound wave passes into our ear canal to the eardrum. The eardrum acts like a drum membrane and causes three tiny bones in the middle ear to move in the rhythm of the sound. This causes a fluid in the inner ear to start moving. The sound waves move the fluid, and this makes tiny hair cells in the fluid move.
These hair cells change the movement into nerve impulses. They are carried to the brain, and the brain interprets them as sound. But it is the different kinds of sound waves that produce different motions in our ear, and different nerve impulses to the brain—and so we hear different sounds!
What Type Of Wave Is Sound?
Sound waves fall into three categories: longitudinal waves, mechanical waves, and pressure waves.