I’ve always wondered how exactly speakers and headphones work. To me, it’s incredibly fascinating how something manages to turn electrical signals into sound, and now that we have evolved from the days of 8-bit music, how those electrical signals can correlate to audio systems playing people’s voices, instruments, and other things with such accuracy. What I found was that it really is quite simple.
As we know, sound waves are generated by vibrations, which due to the back-and-forth nature of the vibration of an object making noise, is a longitudinal wave. These waves have a specific frequency to them, with higher-pitched sounds having higher frequencies and lower-pitched sounds having lower frequencies. Those frequencies, when held for some time and placed one after another, combine to create sounds and/or music as we know it. Those frequencies are encoded via computers or other devices as electrical signals, and these signals are stored or recorded on hardware(such as CDs and cassette tapes) or as software files(like MP3). The speakers themselves are connected to some sort of receiving device, whether that be a computer, phone, DVD player, or even just a standard receiver. This receiving device is capable of reading the file format or piece of hardware that the sound frequencies are encoded on, and wired or wirelessly, they decode and transmit the electrical signals to the speaker or speakers.
Just like with the head of a drum or the string on a guitar, something has to actually vibrate in order to produce the sound. This is where the speaker drivers come in, or the “naked speaker”, so to speak – essentially what you see when you take the speaker grilles off. The vibrations within the driver are cause by a voice coil, essentially an electromagnet. This is attached to a standard magnet that is fixed in place, and as the different electrical signals pass through, the direction of the magnetic field rapidly goes back and forth. This causes the somewhat mobile voice coil to vibrate, and the frequency of those vibrations determines the nature of the sound that is produced.
The voice coil itself, as can be seen above, is connected to the driver cone or the driver dome. Often made of paper or plastic, this is essentially the speaker equivalent of the drum head or guitar string. While the voice coil produces the vibrations themselves, it is the cone that creates the changes in air pressure that causes sound waves to form at various frequencies. It is important to note, however, that most speakers don’t have one driver that covers all frequency ranges, they have three specialized ones: the tweeter driver, which covers higher frequencies(2000+ Hz), the midrange driver, which, as the name implies, takes care of the middle range(200-2000 Hz), and finally, the woofer driver, which operates in the lowest areas of speakers sound(200 Hz and below). When all these various components are put together, they are capable of replicating any sound that can be recorded, from Rick Astley to R. Kelly and everything in between.
I should add that I find it quite interesting how similar the speaker is to our own human diaphragm, with the vibrating membrane and electrical signals. It’s rather funny how human innovation may or may not have taken inspiration from the human body in an indirect way to create such revolutionary devices. I guess in learning how a speaker works, I learned a bit more than I bargained for!