SOUND

SOUND

1. vibrations

   • rarefactions
     • region of low density
   • compressions
     • region of high density and pressure

2. Characteristics

   • longitudinal wave
     • travels in the direction of vibrations
   • catagories
     • audible
       • 20Hz - 20kHz
     • infra sonic
       • frequency lower than 20Hz
     • ultra sonic
       • frequency higher than 20kHz ultrasound possible: sound waves partially reflected when incident on a boundary between 2 materials with different densities. 
       • formula assumes: 1) wave direction perpendicular to boundary 2) speed of sound is approximately same in 2 materials

3. SPEED

   • fluids
     • depends on compressibility and inertia
       • v = sqrt(B/p)