How is Sound Transmitted Through Wires?
- Ji Sung Lee
- Jun 7, 2025
- 3 min read
You get on a public bus. Luckily, you can find a seat to sit on, because you have a one-hour trip in front of you. The sound of the running engine of the bus disturbs you, so you pull your earphones out from your bag. You put them on, and click your playlist, and sound flows into your ears. If earphones didn’t exist, you would have had to sit on the bus without any music, but just the sound of a noisy bunch of people and the engine’s sound.
Earphones have revolutionized how people consume music and sound from their electronic devices. In public places, they also serve as a necessity for maintaining etiquette. They have become a necessity when travelling distances. From the touch of a button, sound travels from the phone up to the eardrums. Speakers have also facilitated the spread of information and public demonstrations, allowing a single individual’s voice to be heard as far as hundreds of meters away. Speaking into a microphone allows amplified sound through the speakers. All of these devices make these functions possible with a few copper wires. However, in all of these devices, sound itself does not travel through the copper strands under the silicon wrappings of wires. Then, how is sound transmitted through them?
Sound and its relation to electrical signals
To start this article, an important concept of sound has to be established before going into the depths: what is sound? In simple terms, sounds are vibrations caused by moving objects. These vibrations reach our ears, and our brains interpret them, letting us hear sound.
To be carried through a wire up to a speaker or an earphone, they must be transmitted as electrical signals beforehand. In speakers and earphones, a device called a diaphragm vibrates (mechanical energy) to create corresponding electrical currents that correspond to the sound wave’s characteristics, such as its amplitude and frequency. For example, a microphone has a diaphragm drive inside its cone-shaped seal, vibrating whenever sound contacts it. This transformation of vibrations to electrical signals is called transduction, done by transducers like microphones.
Transducers
Transducers, by definition, are devices that transform one form of energy into another. For our purposes, transducers transform mechanical energy into electrical energy, or vice versa, to transmit sound into electrical signals. Most of the transducers in microphones use either an electromagnetic or electrostatic technique to convert sound waves into electrical signals.
An electromagnetic technique is used in dynamic microphones. When the diaphragm vibrates, a small magnet oscillates inside a coil attached to the diaphragm. The magnet and coil create an electrical signal by magnetic induction. The dynamic microphone has good linearity, the ability to produce sound accurately over all frequencies, which makes it suitable for high-quality musical reproduction.
Electrical signals travelling through wires
In essence, sound waves hit the diaphragm, which oscillates the coil inside. The magnet inside the coil then creates electrical signals. Then, the next question becomes this: how do these converted electrical signals eventually go through those wires?
Electrical signals travel through wires via the movement of electrons, or a “stream” of electrons. The voltage, provided by the cord that the microphone or speaker is plugged in, provides the push that moves the electrons along the wire. This is what is called an electric current.
The electrical signal reaches the output, translates into vibrations for the diaphragm, and produces sound again, amplified if the output is a speaker.
Conclusion
It’s fascinating how mechanical waves can be transformed into electrical signals and how those signals then reach a bouncing driver and deliver sound to our ears. Next time you pull out your earphones to listen to some music, say thank you to the little magnet that oscillates to provide you an upbeat mood.
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