Sum It Up!
Sound waves are the result of mechanical vibration. All sounds originate from a vibrating object. The vibrating object causes the medium surrounding it (air or water, for example) to vibrate (move back and forth, or up and down).The ruler is an example of a vibrating sound source. When it is struck, a twanging sound is heard and the ruler can be observed to vibrate at a particular frequency (number of vibrations per second) as its free end moves up and down. As the length of the ruler increases, the frequency decreases.
The vibration of the ruler causes the air molecules around the ruler to move back and forth at the same frequency, creating areas of compression (where the molecules are pushed together) and rarefaction (where the molecules are spread apart). The movement of the air around the vibrating ruler transfers the sound energy through the air so that vibrating air enters your ear and hits against your eardrum, causing it to vibrate. In the inner ear, these vibrations are changed into electrical signals and sent to the brain. The frequency of the vibration of the eardrum is interpreted by your brain as a specific sound. As the frequency increases, the pitch (high or low property of sound) becomes higher. |
