How do headphones work? (As in how does electricity get turned into sound)
In: Technology
I don’t know the specifics, but there’s an magnet of some sort that vibrates in response to current. You might notice when you plug them in you get a characteristic humming noise. When you play a song, the magnets are excited and the vibrations cause sound
A trip to an used book store to find the books that used to teach kids to build from scratch radios, speakers and microphones is useful.
It’s really hard to think that there is anything but magic when you have not built from scratch something that turns motion into electricity or vice versa.
YouTube is a great place to watch others doing it, but few channels actually show people building from scratch, because sponsored links are part of how science YouTubers make money.
“Cigar Box Microphone/speaker” might yield some useful results, but some of this is just too old school to have ever been digitized.
ELI5 about basic science is often just better thought of as what experiments can a young person do, and doing them. Even the thermodynamics question about entropy yields to growing seeds or even just crystal under the influence of electric current. Because once you realize that energy input matters, thermodynamics makes a lot more sense, because it aligns with day to day experience.
This has lots of pictures:
https://www.electronics-tutorials.ws/io/io_8.html
A speaker is a kind of transducer which has an electromagnetic diaphragm that makes sound waves by wiggling when signal is applied to the two leads (some voltage and amperage). Alternatively, due to its electro mechanical design can be used as a. Microphone depending on if the two leads have an output signal.
Little wiggles = high pitched sounds
Big wiggles = low bass sounds
Headphones are just speakers writ small, so let’s discuss speakers.
A speaker, fundamentally, is a cone of some sort of material, attached to something called a “voice coil.” The voice coil is essentially just a coil of wire wound around a frame. Electromagnetic theory tells us that driving an electric current through a wire makes a magnetic field that varies with the voltage.
There’s also a permanent magnet attached to the frame of the speaker; when a magnetic current arises around the voice coil, it vibrates because of magnetic attraction and repulsion. This vibration causes the speaker cone to vibrate, and that causes the air to vibrate, which is what sound is.
A pair of headphones is just a really small speaker right next to your ear.
How exactly does a posi trac rear end on a Plymouth work? It just does!
I have a decent understanding of the principles of how speakers work, but the fact that they work as well as they do is still magical to me.
And it’s way more magical when you consider early recording, where it’s basically and anti-speaker (microphone) turning sound into electricity, which then gets written to a wax plate, which can then be mass reproduced using inexpensive vinyl blanks, which can then be played back at nearly the same fidelity as the original sound using a relatively inexpensive machine.
There are three key physical parts to a speaker. A permanent magnet, an electromagnet or “voice coil” (which is only magnetic when a current is being passed through it) and a diaphragm. It works like a [wave machine](https://media.giphy.com/media/fnEofBYPhcBBBxvieO/giphy.gif) except it makes waves in the air instead of water. The shorter the space inbetween the waves (frequency), the higher pitched the sound will be. The bigger the waves are (amplitude), the louder the sound will be.
In order to make a wave, an electrical pulse is sent through the electromagnet, which pushes/pulls it away/towards the permanent magnet. The diaphragm, [which is what you see when you think of a speaker](http://ffden-2.phys.uaf.edu/webproj/212_spring_2017/Jesse_Drick/Jesse_Drick/giphy.gif), is attached to this and is pushed/pulled along with the electromagnet. The large area of the diaphragm creates the waves in the air which are the sounds you hear. The opposite happens in your ear. Your ear drum takes these waves in the air, transmits them to your inner ear as vibrations, which your cochlea converts into electrical signals that are sent to your brain.
If you are asking how electricity gets turned into sound from a perspective of how does say a sound file morph into actual music you can hear, there are specialized circuits (we used to just call them ‘sound cards’ but they aren’t discrete cards anymore, just sections of circuit boards) which can take a binary input and output signals a speaker can understand using a standard jack. It is one of the first things computer guys wanted to sort out before PCs became really popular. I remember updating firmware for ‘soundblaster’ cards so I could listen to realistic engine noises in Microsoft Flight Simulator.
Some really nice 3D animated infographics by Jacob O’Neal on how speakers make sound: https://animagraffs.com/loudspeaker/
There’s quite a few interesting takes, but definitely not ELI5. Alot of assumptions are being forced on a 5 year old, from EM theory, difference between current, electric current and voltage. That all sounds are basically just vibrations in the air, hence why sound is muffled in water and even moreso in space.
I think an appropriate ELI 5 to start is that sounds are caused by air vibrating/shaking. That’s why snapping your fingers make that sound, doing so vibrates the particles to make a sound.
Then magnets. We all know magnets can attract and repel. Without getting too into electromagnetism, it turns out some materials can be made into magnets when passing electricity through it- hence electro+magnet.
Now, using electricity we can make an electromagnet be either repulsive or attractive (remember the North/South poles?). These electromagnets would interact with normal, non-electromagnetic, magnets causing some vibration inside your headphones.
Headphones, and anything that produces electrical based audio, would have these electromagnets that would vibrate back and forth from being attractive and repulsive, these vibrations inside your headphone produce the sounds in your headphones.
So to *recap*:
•Sound is vibration.
•Electromagnets are naturally non-metallic objects made magnetic using electricity.
•Magnets can be attractive or repulsive depending on their polarity (North/South Poles).
•Electromagnets can alternate between attractive or repulsive by changing electrical current.
•There’s a normal, non-electromagnetic, naturally magnetic in the headphones.
•Electromagnet would constantly alternate between attracting and repulsing the normal magnet. This causes vibrations.
•Vibrations made create the sound in our headphones
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