How+does+sound+change?

=How does sound change?=

Sound waves have many characteristics about them, all of which are easy to change or manipulate to do what humans want. Three major aspects of waves that if altered, change the sound, are pitch, speed, and volume. Sound also undergoes a change by an act called the Doppler Effect.

Pitch: Pitch is the sound perceived by our ears as the bones in our ear vibrate. Pitch is changed by changing the frequency(cycles/sec) of a sound wave. The video below shows two tuning forks that have different frequencies of vibration. Listen closely to hear the differences in pitch, or change in frequencies between the two different tuning forks.

media type="file" key="Pitch.mov" width="300" height="300"

Speed: (See Refraction) The speed of sound changes in two different ways. In air, the speed of sound can change due to temperature. Sound can also change speed as it moves through different mediums.
 * Substance || Speed of Sound (m/s) ||
 * Air (0degC) || 331 ||
 * Air (20degC) || 343 ||
 * Water(15degC) || 1500 ||
 * Wood || 3800 ||
 * Steel || 5800 ||

Volume: Volume is determined by the amplitude/intensity of a sound wave. The higher the amplitude of a wave, the more energy there is in the wave. The more energy there is in a wave, the higher its intensity, thus making the sound appear louder to the human ear. In the video below, the tuning fork (having the same frequency in both hits) hits the striker. The next time it hits the striker harder, transferring more energy into the tuning fork, making it louder. media type="file" key="Volume.mov" width="300" height="300"

Doppler Effect: (See Doppler Effect) The Doppler Effect is a change in frequency due to motion. This motion may come from the producer of the sound, the observer of the sound, both, or even motion of the medium. As the sound approaches, it has a higher frequency but as it recedes it has a lower frequency. In the picture below, the object is moving to the left. This makes the frequency in front of the object much higher than behind the object.

http://upload.wikimedia.org/wikipedia/commons/d/d3/Doppler_effect.jpg