Loudspeakers & Headphones

• How does a loudspeaker produce a sound wave?


  -The coil's magnetic field interacts with the magnetic field from the permanent magnet

  -These magnetic fields attract or repel. This produces a resultant force, the current moves

  -When the current switches direction, the direction of the force on the cone reverses. The cone moves in and out, generating sound waves
• Describe the picture

  -This is a moving coil loudspeaker

  -We find these in stereos, and much smaller ones in headphones

  -As you can see there is a cone, which has a coil of wire wrapped around one end

  -The coil of wire it attached to an AC electrical supply

  -We also have a permanent magnet that goes inside the coil of wire.

  
• What changes can we make to change the sound produced from a loud speaker?

  -Changing the frequency of the AC supply changes the frequency that the cone vibrates.

  -higher frequency produces a higher pitch sound

  -lower frequency produces a lower pitch sound

  -Changing the size of the current changes the size of the amplitude of the vibrations, smaller amplitude = quieter sound, larger amplitude= louder sound