Sound Waves

Sound is a vibration.

Compression: where air molecules are forced closer. Rarefaction: where density and air pressure becomes lower than normal because air molecules are forced to spread out.

Sound = vibrations are parallel to wave motion. (longitudinal wave) When graphed: crests = compressions troughs = rarefactions.

Frequency = # of cycles per sec Audible Sound = 20 - 20,000 Hz <20 Hz = infrasonic waves >20,000 Hz = ultrasonic waves.

Tone Test http://homerecording.about.com/od/homestudiobasics/a/test_tones.htm

When frequency , so does the pitch. Pitch is how high or low it sounds.

Speed of waves depends on the medium and temperature. Sound waves travel fastest in solids and slowest in gases due to the spacing of the molecules. As temperature increases, particles collide more frequently which makes sound travel faster.

Doppler Effect – a frequency shift that is the result of relative motion between the source of waves and an observer.