Sound Wave

Characteristic of Sound Wave

  1. Sound wave is a series of compression and rarefaction of layers of air molecules repeatedly through space.
  2. The forward and backward vibration of the air molecules in the direction of motion of a sound wave shows that sound is a longitudinal wave.

Propagation of Sound Wave

  1. Sound wave is a mechanical wave that requires a medium for its propagation. Therefore sound wave cannot propagate in vacuum.
  2. The medium for propagation can be solid, liquid or gas.
  3. Sound waves propagate fastest in solid and slowest in gas.

Type of Sound Wave

  1. Human ear is capable of hearing sound with frequency in the range of 20Hz – 20,000Hz, and the sound wave with frequency in this range is called an audio/Sonic wave.
  2. Sound wave with frequency lower than 20Hz is called an Infrasonic Wave.
  3. Sound wave with frequency higher than 20,000Hz is called an Ultrasonic wave.

 Infrasonic Audio/Sonic  Ultrasonic 
 <20Hz  20Hz – 20000Hz  >20 kHz

Speed of Sound Wave

  1. Speed of sound wave in solids is greater than in liquids, which is greater than in gases.
  2. Speed of sound in air is not affected by pressure, but is affected by the temperature.
  3. As temperature increases, speed of sound in air (and other gases) is also increases.
  4. Sound usually travels more slowly with greater altitude, due to reduced temperature.
  5. Speed of sound can be calculated by the equation