1. Sound

2. The origin of sound All sound are produced by the vibrations of material objects. Our voice results from the vibration of our vocal chords. Sound travels as a longitudinal wave. We call our impression of the frequency as pitch. High pitch sound has a high frequency Low pitch sound has a low frequency We can hear pitches to frequencies form 20 to 20000 Hz. As we get older, this range shrinks Sound waves under 20 Hz are called infrasonic Sound waves above 20000 Hz are called ultrasonic.

3. The nature of sound in air Condensation: a pulse of compressed air Rarefaction: a disturbance that causes a zone of lower- pressure air. Sound_Waves.asf The speed of sound At 20  C, sound travels at about 340m/s Speed of sound depends on medium and temperature. Sound cannot travel through a vacuum. The_Speed_of_Sound.asf

4. Natural Frequency When an object composed of an elastic material is disturbed, it will vibrate at its own special set of frequencies. Resonance Occurs when an object is forced to vibrate at its natural frequency. When the frequency of forced vibrations on an object matches the object’s natural frequency, a dramatic increase in amplitude occurs. http://www.hep.uiuc.edu/home/mats/WCIA/wcia_0304 30_2.wmv http://www.hep.uiuc.edu/home/mats/WCIA/wcia_0304 30_2.wmv YouTube - breaking a wine glass using resonance

5. Resonance is not restricted to wave motion. The Tacoma Bridge disaster in 1940 was caused by wind- generated resonance. YouTube - Tacoma Bridge Interference Read p376 Beats Periodic variation in the loudness of sound Occurs when two tones of slightly different frequencies sound together. Read p377.

6. Ultrasound Imaging_Technology___Ultrasound.asf Using sound to remove kidney stones http://www.stmary.ws/highschool/physics/home/vide os/waves/kidresnc.mov http://www.stmary.ws/highschool/physics/home/vide os/waves/kidresnc.mov

7. Sound