More or less we all listen to songs. When we play a song, sound come out from speakers, it may be a Loudspeaker of a woofer, Monitor speakers, cell phone speakers, and speaker of headphones or may be a tweeter. We can hear the voice of human and many other instrumental sounds through it which is recorded and playing in a music player device. Speaker is a device which creates physical sound waves from a digital sound files. But how does it do that? How can a mp3 file saved in a machine become a real voice that we can hear?
How does speaker work?
Basically speakers convert electricity to sound waves. Music players send electric pulses of different amplitudes and frequencies rhythmically to the speakers through the wire that is connecting the speaker and the music player device. That electric pulses become sound waves and audible to us.
We know sounds come out when two things bombard with each others. Actually when two things bombard with each other, the surface of those two things get kinetic energies and start moving back and forth i.e. it starts vibrating. And sounds come from vibration as a vibration creates wave in the air and that waves strike our ear drum and let us experience a sound in our brain. Sound of a Guitar comes when we tweak the string of it and make it vibrate, sounds come from a drum when we strike the skin of the drum and the skin start vibrating. Similarly sound comes from a speaker when the paper layer on it(Diaphragm) start vibrating.
What makes the diaphragm vibrate?
To know this in details let’s look out what are the parts there in a speaker.
- A permanent Magnet: Every speaker has a round shaped permanent magnet.
- Two metal plates: Two sides of the magnet are covered by metal plates. The plate presents at the outer side of the magnet called bottom plate and it contains a metallic cylindrical pole which is inserted in the middle hole of the magnet called pole piece. And the plate present at the inner side of the magnet is called Top Plate.
- Voice coil: A copper wire coil is made around the gap between the pole piece and the wall of the magnet. Its two terminals are brought out and placed in the basket part for connection.
- Diaphragm: It’s the conical shaped strong paper material which one is vibrate to create sounds. Generally it is black in colour. It’s center is connected with the voice coil and the basket.
- Basket: It’s a metal frame around the speaker, starts from the top plate and holds the diaphragm in a conical shape
- Spider: It’s a soft and flexible suspension holds the voice coil. If we push the middle part of the diaphragm where the coil is located with our finger, the diaphragm will come back or will be restored to its position again. The spider suspension does that. It helps the coil to bring back when it goes down to the pole piece.
- Dust cap: A dome shape is present at the center portion of the diaphragm and over the voice coil. It protects the voice coil from dust.
According to Fleming’s law: If a current carrying conductor is placed in a magnetic field, there will be a force acting on the conductor. Voice coil of the speaker is placed around the pole piece which is surrounded by the permanent magnet. So the coil is place inside a magnetic field. And when we connect the two terminal of the coil with a Stereo device, that device send electric signals to the coil and the coil becomes a current carrying conductor.
In another way, when current flows through the coil, the coil becomes an electro magnet, and due to the polarity concept of magnet (Same pole of two magnets repel each other and opposite poles attract each other) the permanent magnet either pulls or repel the electromagnet (The voice coil). The permanent magnet is fixed, so the voice coil moves back and forth when magnetic force experienced. And the center of the diaphragm of the speaker is fixed with the voice coil. So when coil moves, the diaphragm also moves and vibration gets created in it. Due to this vibrations sounds come out.
When current with high Amplitudes or bigger pulses of electricity flows to the coil, the diaphragm moves more and creates sounds of higher volumes. If the electric pulses will be smaller, then the volume of the sound comes out of the speaker will also be lower.
Now in market very advanced speakers are available which are sensitive, powerful and more efficient. Power of a Speaker is measured by a unit Watt. And the sensitivity of the speaker is how much output one speaker can give with unit inputs.
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