Propagation of sound

• Propagation of sound


  1. Sound moves through a medium from the point of generation to the listener

  2. When an object vibrates, it sets the particles of the medium around it vibrating

  3. The particles do not travel all the way from the vibrating object to the ear

  4. A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position

  5. It then exerts a force on the adjacent particle

  6. This process continues in the medium till the sound reaches your ear
• The disturbance created by a source of sound in the medium travels through the medium and not the particles of the medium.
• A wave is a disturbance that moves through a medium when the particles of the medium set neighbouring particles into motion
• The particles of the medium do not move forward themselves, but the disturbance is carried forward
• This is what happens during propagation of sound in a medium, hence sound can be visualised as a wave
• Sound waves

  Mechanical waves characterised by the motion of particles in the medium
• Air is the most common medium through which sound travels
• Propagation of sound in air

  1. Vibrating object moves forward, pushing and compressing air in front of it creating a region of high pressure (compression)

  2. Vibrating object moves backwards, creating a region of low pressure (rarefaction)

  3. As object moves back and forth rapidly, a series of compressions and rarefactions is created in the air

  4. These make the sound wave that propagates through the medium
• Compression


  Region of high pressure
• Rarefaction


  Region of low pressure
• Pressure is related to the number of particles of a medium in a given volume
• More density of the particles in the medium gives more pressure and vice versa
• Propagation of sound can be visualised as propagation of density variations or pressure variations in the medium