7.2.4 Loudspeakers HT

In this lesson, we will explore how moving-coil loudspeakers and headphones work, focusing on their mechanism and the conversionThe act of changing someone's religion. of electrical signals into pressure variations in sound waves.

The Motor Effect in Loudspeakers and Headphones

Loudspeakers and headphones are devices that use the motor effect to convert variations in current in electrical circuits to the pressure variations in sound waves. These devices rely on the motor effect, where the interaction between a magnetic field and a current-carrying coil produces mechanical motion.

Moving-Coil Loudspeakers

Moving-coil loudspeakers are the most common type of loudspeakers used in audio systems. They consist of a permanent magnet, a coil of wire (voice coil), and a diaphragm.

• The voice coil is attached to the diaphragm, which is typically a cone-shaped or dome-shaped membrane.
• When an audio signal passes through the voice coil, it creates a varying current that interacts with the permanent magnet's magnetic field.
• According to the motor effect, the force on the voice coil causes it to move back and forth, thereby vibrating the diaphragm and generating sound waves.

Headphones

Headphones operate on a similar principle to loudspeakers but on a smaller scale, delivering sound directly to the ears of the listener.

• They consist of miniature moving-coil loudspeakers located within each earcup.
• The voice coil in each earcup interacts with the permanent magnet to produce sound waves.
• When an audio signal is applied to the voice coil, it vibrates the diaphragm within the earcup, generating sound waves that can be heard by the listener.

Conversion of Electrical Signals to Sound Waves

• In both loudspeakers and headphones, the electrical signal from an audio source causes variations in the current flowing through the voice coil.
• These current variations interact with the magnetic field, resulting in the motion of the voice coil and the subsequent movement of the diaphragm.
• The diaphragm's vibrations create pressure variations in the surrounding air, producing sound waves that are perceived as sound by our ears.

Conclusion

Loudspeakers and headphones rely on the motor effect to convert electrical signals into pressure variations in sound waves. Moving-coil loudspeakers and headphones utilise the interaction between a magnetic field and a current-carrying coil to generate mechanical motion and vibrate a diaphragm, producing sound waves.