I was always fascinated by how earphones work. What's there in such a tiny device which beautifully produces mechanical output from electrical pulses. But when I finally opened one, I found there's nothing astonishing but the fundamental of propagation of sound wave- medium- sound waves travel in a medium (air). The earphones move the air present inside according to the highs and lows of the electrical pulses and the compression and rarefaction of air produces sound.( We already know that!) So, here's how it does.
1 Teacher Note
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Tools Needed
Dismantling an earphone is quite easy. You would just need:-
2). Paper Cutter
Step 2: Dismantle Process
It would be easy if you would cut the earbuds and the jack to separate them first.
Then, using a cutter, start cutting the seal of the earbud. You don't have to go around it, just cut persistently at a single spot long enough to break the seal. The whole front case would pop out automatically. Now, you can take the diaphragm, coil and the magnet apart.
The microphone can also be dismantled in the same way as the earbud.
The most interesting part of earphones (for me) is the audio jack. I wanted to see how the connections are made. So, I peeled off the plastic around the jack. It's not easy and I would recommend adult supervision if you're young, 'cause there are two layers. One is the rubber which you can easily remove using a cutter. And another one is hard plastic. For this, I used a candle to heat up my cutter and sliced the plastic cover. It takes time and though it looks clumsy, but it's clear enough to understand the connections.
Step 3: Parts Inside
1). External case
2). Front case
3). Diaphragm (plastic sheet)
4). Coil- also called 'voice coil'- attached to the diaphragm (forms the winding of electromagnet)
5). Neodymium magnet (smaller circular piece)
6). Core of electromagnet (larger circular piece)
Step 4: Working- 1). Earbuds
First of all, earphones/ headphones are of two types:-
a). Closed-back- The front casing of earphones would, obviously, have holes. But if the external back casing doesn't have any holes, than such earphones are closed-back ones. These prevent the external noise from interfering and no sound escapes from it.
b). Open-back- The external back casing has holes. These are more preferred as they sound better, but has the drawback of sound escaping outside and the external noise penetrating inside.
The earphones are miniature loudspeakers, literally the only difference between the two is 'size'. The permanent magnet inside the earphones is the only stationary part. While the electromagnet (i.e. coil + iron core) is moving. The electric signals received from a system are sent to the electromagnet which is either repelled or attracted by the permanent magnet according to the magnetic field induced. So, the electromagnet moves back and forth which also makes the diaphragm, attached to it, to move accordingly. If you remove the magnet too from the earbud, you would see a pole piece. This is used to concentrate the field generated by the electromagnet.
Step 5: Working- 2). Audio Jack
An audio jack comes in various lengths, sizes and configuration. Mine is a 3.5mm TRRS jack. An audio jack can have 2,3,4 or 5- conductors (TS, TRS, TRRS, TRRRS). TRS stand for Tip Ring Sleeve.
In my jack, the tip is connected to the left earbud, first ring to the right earbud, second ring to the mic and the sleeve is used for ground connection. As you can see in the above picture, two wires(one from each earbud) are connected to the ground, one runs to the tip and the other to the first ring. This configuration can vary for different companies. However, you can check it using a multimeter. For more info, visit: https://en.wikipedia.org/wiki/Phone_connector_(aud...
In many audio jacks, the only difference is the position of mic and ground. They are usually reversed.
Using a TRS connector for TRRS socket or vice versa can damage your device. So, please be careful in choosing an appropriate earphones.