properties & detection of sound

• Sound waves are longitudinal, meaning they compress the medium through which they travel.
• A pressure oscillation that is transmitted through

  matter is a sound wave.

  Sound waves move through air because a vibrating

  source produces regular variations, or oscillations,

  in air pressure.
• The frequency of the wave is the number of

  oscillations in pressure each second.

  The wavelength is the distance between

  successive regions of high or low pressure.
• Sounds with a frequency of 20 Hz and lower are called

  infrasound

  Sounds with a frequency of 20 kHz and higher are

  referred to as ultrasound (or ultrasonic sound)
• The change in frequency of sound caused by the

  movement of either the source, the detector, or both is

  called the Doppler effect.