chapter 12

• sound


  a longitudinal wave travelling created by a vibrating source

  a forward and backward vibration is passed on to the air particles

  • causes alternate regions of the air particles to be compressed and extended
  • the extended regions are called rarefactions while the compressed regions are called compressions

  since sound waves relies on the passing on of motion from a group of molecules to another group through collisions, it cannot propagate in vacuum space
• to human ears


  loudness of a sound is subjective
• loudnessand amplitude


  a device that gives an objective reading on the loudness is called a sound level meter

  the larger the amplitude, the louder the sound
• pitch and frequency


  the higher the frequency, the higher the pitch
• audible and inaudible sound


  human ears can hear sound from 20Hz to 20000Hz, known as the audible range

  frequencies below 20Hz are called infrasound

  frequencies above 20000Hz are called ultrasound
• reflected sound


  echo
• echolocation


  calculating of distance from the sound emitter to the reflecting surface
• ultrasound


  a sound frequency above the upper limit of human audibility range

  sonar technologies

  • sonar (sound navigation and ranging)
  • imaging internal organs
  • for breaking up kidney stones and cancer treatment