Loudspeakers and Microphones

• Loudspeakers - take electrical signals and use the motor effect to convert them into vibrations, which then generate sound waves.

  
• Microphones - detect vibrations caused by sound waves and use the generator effect to convert them into electrical signals.

  
• Loudspeaker diagram:

  A) Magnet North

  B) Magnet south

  C) Coil

  D) Cone

  
• How a loudspeaker works:

  1. An alternating current flows through the wire and creates a magnetic field in the coil.
  2. magnetic field of the coil interacts with the magnetic field of the permanent magnet
  3. The interacting magnetic fields will exert a force on the coil causing it to move back or forth along the permanent magnet
  4. As the current is alternating, its magnetic field and the force it experiences will also alternate. This means that the coil of wire and cone rapidly move back and forth (vibrate)
  5. Vibration cause pressure variations in the air- which are sound waves.
• Microphone diagram

  A) North

  B) South

  C) Coil

  D) Diaphragm

  
• How Microphones work:

  1. Sound waves hit the diaphragm
  2.  diaphragm and coil of wire moves
  3. As the wire is moving within the magnetic field of the permanent magnet, it will generate a current
  4. The frequency and amplitude of the sound waves will determine how much the diaphragm vibrates, and therefore determine the frequency and amplitude of the current.