Ch 13 Sound Sound Waves Longitudinal Waves Compression

Ch. 13 Sound

Sound Waves Longitudinal Waves Compression – region of high density and pressure Rarefaction – region of lower density and pressure

Sound Waves Audible sound – frequencies humans hear (20 Hz – 20, 000 Hz) Infrasonic waves – frequencies below 20 Hz Ultrasonic waves – frequencies above 20, 000 Hz

Sound Waves Pitch – the perceived highness or lowness of a sound Frequency determines pitch

Ultrasonic Waves Can produce images due to their short wavelengths Waves are partially reflected when they reach a boundary between materials with different densities Many medical uses Dolphin echolocation

Sound Waves The speed of sound depends on the medium Sounds travel fastest through solids Sounds travel slowest through gases The speed of sound also depends on the temperature of the medium Sounds travel faster as temperature increases

Sound Waves Sound waves travel in three dimensions Assume their shape is spherical Represented graphically by a series of circles

Sound Waves Each circle is a wave front (center of each compression)

Sound Waves Rays are perpendicular to wave fronts and show direction of wave motion

Doppler Effect Relative motion creates a change in frequency The frequency shift is called the Doppler Effect