How Record Players Work: The Science Behind That Beautiful Sound, Simplified
The eighth wonder of the world is sitting down in the evening with a cup of whiskey on the rocks with the strum and yodel of ol' Hank Williams crackling through the record player. It's the closest I could come to experiencing what it would be like listening to him on the radio.
If you don't like Hank or country music, imagine the serenading sounds of Sinatra, Beethoven, Anne-Margret, Ben E. King, or Franki Valli crackling through the speaker. No matter who you pick, it's going to be a delicious sound with just the right amount of noise, music, and feedback to transport you back to the mid-20th century.
After recently watching The Current War (featuring Dr. Strange and Spiderman before they were Dr. Strange and Spiderman), I did some light research on Edison and his phonograph and asked the question, "Cool, but how?" That led me down a rabbit hole of trying to understand how sound gets recorded on a vinyl disk and then how it can somehow play back at the exact right frequencies and pitch at a volume loud enough to be heard by our delicate little ears. The results of questioning, studying, and following that rabbit hole gave birth to this article. I'm happy I understand how it works and delighted to share my discovery. Let's begin.
In reality, a record player is pretty simple:
- A record has grooves
- A needle follows the grooves and makes a sound
- That sound is amplified
- Boom - you have a record player
But that wasn't good enough for me, which was unfortunate because that is what most of the articles said, in some form or another.
I still had many questions:
- Where does a record player come from?
- How does the sound get recorded into the record?
- How does the needle actually make the sound?
- How does the sound travel from the needle to the amplifier, which is seemingly hidden away?
Before I could begin to truly understand how a record player works, I first had to get down and dirty with the science of sound and, more specifically, what are sound waves and how do they work?
First, the science of sound
Sound is a wave that disrupts the air or other medium it's traveling across. When you talk, the particles in the medium vibrate back and forth and carry the sound wave. That wave rides the vibration of that medium into your ear and vibrates the ear drums which tell your brain, 'Hey! Something's going on over here, pay attention.'
Since the sound wave rides the medium, if there is no medium, there can be no sound. This is why there is no sound in space. There is virtually no air in space and, therefore, nothing to carry the sound that's made. So I guess that answers the question, if a tree falls in the middle of space and no one is around to hear it, does it make a sound?
Sound waves have three characteristics:
If you have a high frequency sound vibrating the particles in the air, the particles move back and forth really, really fast. When you have a low frequency sound, the particles in the air vibrate much slower. The wavelength, frequency, and amplitude can be thought of as "data" which carries the information about what the noise sounds like. Your eardrums are able to read that "data" and tell you what something sounds like. So if someone starts talking in a higher pitched voice, the wavelength will get higher thus telling your ears, "This noise is a higher frequency."
To recap this section:
- Sound is a wave that vibrates the particles in the medium it’s heard through.
- The sound wave rides the medium into your ear, vibrating the eardrums.
- The movement of the particles match the wavelength, frequency, and amplitude of the original vibration, which allows you to hear different things.
Now that we understand what sound is, we can dive into the history of record players and understand how a vinyl disc contains the lovely notes of Frank Sinatra and Anne Margaret.
The history of that lovely sound machine
Recording human sound was only possible after one understood what sound is and how we hear it, both of which we just learned. But in the 1850s, this information wasn't as available. But lucky for us, a printer named Edouard-Leon Scott de Martinville came across a biology book that piqued his interest in understanding how sound works. He saw from the textbook that sound traveled through the ear and vibrated the eardrum. Scott had also published a book on the history of shorthand writing, which at the time, was how voices were "recorded." But Scott would change that. Kinda.
As he combined his newfound interest in human anatomy and shorthand writing, he wondered whether or not a machine could write the sound waves instead of a person. Pretty neat idea if I do say so myself. So, in 1857, twenty years before Edison and his phonograph would come out, Scott was awarded a patent for a machine that recorded sound. He called this machine "the phonautograph."
But what Scott didn't add to his machine was a way to play that sound back. It seems obvious to us now, but Scott assumed that just as stenographers read symbols from shorthand writing, humans would be able to read the waves the machine recorded. Although that never happened, Scott took a giant leap forward in the history of recording sound and the central idea of his machine still lives on today in record players.
Record players are a close cousin to the gramophone, and the gramophone is a close cousin to the phonograph. Though the words are often used interchangeably, the devices are all slightly different. It's similar to the difference between a truck and a car. For the most part, they're the same, but the truck can do some things your average sedan can't.
A phonograph was a device used to record sounds and play the recorded sounds back. A horn was attached to a piece of rubber that allowed it to vibrate freely. On the other end of the horn was a needle that moved in tandem with the vibrations from the horn. Pressed against the needle was a piece of tinfoil wrapped around a metal cylinder. The metal cylinder was fixed to a hand crank which would rotate as the crank was manually turned.
When someone spoke into the horn, they produced sound waves in the air (remember how sound works?) These waves caused the horn to vibrate slightly. Those vibrations moved the needle in a corresponding fashion. As the hand crank turned, the tin-foil-wrapped cylinder rotated against the needle, allowing the needle's vibrations to etch a pattern into the tinfoil.
The hand crank is an important piece to this sound puzzle. If the crank wasn’t turned, the waves would be etched right on top of the previous wave. It’s like when you write something on paper, you need to move your hand. If you don’t, your letters will just be written over one another like the leaning tower of letters. Ha.
If you're a bit confused as to where the vibrations came from and how they correspond to the actual recording of the sound, don't worry because I was too. This is what held me up for a long time. But recall that all sound is, is vibrations. When you talk, you're vibrating the air in a certain pitch, tone, and frequency. When someone spoke into the horn, instead of those waves vibrating someone's ear canal, they vibrated the needle, matching the tone, pitch, and frequency that they were capturing.
Reminder: There was no electricity involved here. This was a purely analog piece of technology.
To play the sound back, the process is simply reversed. The needle turns the etched pattern back into vibrations, which run up the horn and plays back the sound. Pretty cool right?
Similar to the phonograph was the gramophone. The big difference between the two, though, is that the gramophone couldn't record sound. It only played recorded sound back. Thinking about it in terms of the phonograph, it was only the second half of the process. As you could imagine, a gramophone looked much closer to our modern day record players than the phonograph. A gramophone was a better listening device than the phonograph because it didn't have the added variable of the up-and-down movement while recording like the phonograph did, which often caused recording issues.
The "disks" first used in gramophones were metal or shellac, which are a different material than modern-day vinyl records. And this brings us to the difference between a gramophone and a record player. A record player is a more modern gramophone and plays vinyls while a gramophone plays metal or shellac records. Though I'm not a stickler for the exact definition of things like the "Don't you mean Frankenstein's monster" guy, I thought it would be helpful to break those down.
The most important thing to understand in this section is the phonograph and how it works because it answers some of the technical questions about how sound gets recorded onto a record and how modern day record players work.
Next, let's move on to understanding how a record gets the sound recorded on the vinyl for later playback.
How a vinyl record gets sound recorded on it
Similar to Edison's original phonograph, vinyl records get their sound etched in them by converting the electrical waveform of the music to an analog waveform that vibrates a needle. The electrical waveform carries data about the music, like its wavelengths, frequency, and velocity. Essentially, it's a digital vibration.
Regarding the actual process of recording the music, it's essentially a reverse record player. There is a master copy of the vinyl record on a turntable. That turntable has a needle which is connected to a machine. The machine contains the "digital vibration" of the music. The "digital vibration" of the music gets converted into an electrical current (more on how that works in the next section) and that current tells the needle how to vibrate, which etches the record with the grooves you're used to seeing on a vinyl record.
That record is usually stamped with an inverse record that gets an imprint of the master copy. They use that to stamp all the other records before they get shipped out for us to enjoy.
If you're confused here on how the science behind it works, just keep reading. I go into much more detail in the next section, but wanted to give you an idea of how sound gets on the record before we look at how sound gets out of the record.
How the sound from the record gets played back
Now that you understand how the sound gets recorded onto the record, we can reverse-engineer that process to understand how it's played back with just a few more variables.
Exactly like the phonograph described before, the stylus is inserted into the grooves of the record, which hold the vibrations of the recorded sound (we learned this in the last section). As the record spins, the stylus "reads" the information stored in the grooves and vibrates according to the recorded frequency, pitch, and tone. So far, this is no different from how the phonograph played the sound from the tinfoil. Instead of taking vibrations from the horn and playing those back, it's taking the vibrations from the recorded sound on the record player and playing that back.
What got complicated, for me at least, was understanding how those vibrations moved up the tone arm, turned into an electrical signal, raced through the amplifier, and came out of the speakers.
To understand how that all works, we have to introduce a bit of physics, specifically Faraday's Law of Induction.
Inside the body or hidden end of the tone arm, opposite the stylus, are two important components, without which we would not be able to amplify the sound. Those are a magnet and a coil. These two components create an electric current.
To understand how they create an electric current, we have to understand Faraday's Laws of Induction, which state that:
- Whenever there is a change of force between a magnet and a coil, an electromotive force (emf) is created.
- The strength of the emf is directly proportional to how the magnet moved in relation to the coil. The faster the magnet moved, the stronger the signal and vice versa.
Faraday's Laws explain how an electrical current can be created by something that isn't electric. Pretty handy for what we need right about now, huh? If you recall, we need some way to turn the mechanical energy from the vibrations (audio waveform) to an electrical energy that can be sent to the amplifier and out the speaker.
As mentioned previously, record players have a coil and a magnet on the tone arm, opposite of the stylus. When the stylus moves, it moves the attached magnet, which moves relative to the coils, creating an electrical current (Faraday's first law) identical to the audio waveform (Faraday's second law).
That electrical signal is sent to the amplifier, which increases the strength of the current. That current is then sent to the speakers, which vibrate in accordance with the electrical current. If you've ever seen speakers play really loud, bass-filled music, you can see how they bounce back and forth. This mimics the vibrations caused by someone talking and displaces the surrounding air. The sound waves created by the speakers ride the medium into your eardrums and cue the brain to start working. The speakers know how much to vibrate because they are getting the instructions from the original vibrations that were recorded into the record and that the stylus is now reading.
The stylus, tone-arm, magnet, and coils are all parts of what the science community calls a "transducer." A transducer is just a $3 dollar word for describing something that converts energy from one form to another. In our case, it's converting the mechanical energy of the vibrations into electrical energy.
I have a record player and when researching for this article, I was listening to the record very closely and turning the volume up and down. I got to a point where it was so low that the amplifier wasn't on, so the speakers turned off, but the record player was still spinning. If I leaned in real close to the stylus, I could hear the raw vibrations caused by the stylus 'reading' the grooves of the record. I thought that was pretty fascinating! As I slowly turned the volume up, I could hear the speakers overtake the raw sound of the record and stylus doing their thing.
Putting it all together
Step 1: An artist records a track into a computer.
Step 2: That computer turns those "digital vibrations" into instructions. The instructions tell the needle how to vibrate. This is how a record gets sound recorded onto it.
Step 3: That record is placed on a record player. The needle from the record player vibrates exactly the same way the original digital file the artist recorded "vibrated.”
Step 4: Those vibrations (mechanical energy) are converted into an electrical current via the moving magnet and coil on the opposite end of the tone arm. This current matches the vibrations from the original file as well.
Step 5: That current is sent to the amplifier, which increases the amplitude of the electrical current and sends that amplified current as instructions to the speakers.
Step 6: The speakers displace the air in exactly the same way the artist originally displaced the air when they recorded the audio into the computer.
Step 7: Any species with ear drums enjoys that sweet sound.
If I'm not mistaken, that seems to answer all the previous questions about our record player and how everything works together. I'm truly amazed at this little device and had a joy understanding all the moving pieces, literally.