1. Waves / Sound Physics

2. Waves Wave motion is the means of transferring energy through a medium without the material itself moving along with the energy. Mechanical Waves require a physical disturbance in an elastic medium. Sound Electromagnetic waves involve electric and magnetic disturbances and do not require any medium. Light, radio waves, heat

3. Classifying waves Transverse waves transfer energy in such manner to cause the material to vibrate perpendicular to the direction of wave motion. Longitudinal waves transfer energy in such a manner to cause the material to vibrate parallel to the direction of wave motion.

4. Wave Words Wave terminology trough crest amplitude wavelength (l) * for a longitudinal wave the crest is called a compression and the trough is called a rarefaction

5. ELECTROMAGNETIC RADIATION AN OSCILLATION OF ELECTRICAL AND MAGNETIC FIELDS SOME COMMON CHARACTERITICS SPEED: WAVELIKE IN NATURE E F L I E C L T D R I C LOW FREQUENCY (  ) HIGH FREQUENCY  = m  = s -1 OR Hz A -A

6. Speed of Sound The speed (v) of sound through a material depends on the elasticity and the density of the material. More elastic  restoring forces  speed More dense  resistance to motion  speed

7. Periodic Wave Motion Wavelength (λ) is the distance between two adjacent particles that are in phase. Frequency ( f ) is the number of waves (or cycles) per unit of time. It is commonly measured in hertz (1 Hz = 1 cycle /second). Period ( T )is the time per cycle, the reciprocal of the frequency. v = λf f λ T

8. Wave interference Superposition principle states that when two or more waves exist simultaneously in the same medium,the result is the algebraic sum of each wave. Constructive interference produces a resulting wave of greater amplitude. Destructive interference produces a wave of lesser amplitude.

9. Sensory effects (Perception) of sound Physical property intensity frequency waveform Perception loudness pitch quality

10. Sound intensity Intensity is the measure of power per unit of area. For a point source, the effective area would be a sphere with a radius equal to the distance from the source. Intensity levels compare the level of sound to the hearing threshold. The ratio is described in decibels. db = 10 log ( I / 10 -12 W/m 2 )

11. Sound frequency Infrasonic frequencies less than 20 Hz Audible sound frequencies between 20 Hz and 20,000 Hz Ultrasonic frequencies greater than 20,000 Hz

12. Doppler effect A change in the observed frequency as a source of sound moves relative to the observer. f o = f s x v + v o v - v s f o = frequency heard by the observer f s = frequency from the source v = speed of sound (740 mi/hr or 330 m/s) v o = spped of the observer v s = speed of the source