Course:PHYS341/2022/Physics of Vinyl Records
Introduction and History
Vinyl records are some of the earliest techniques we have been documenting and playing back sound. They are a storage medium of sound waves imprinted with a needle onto a wax or polyvinyl chloride [PVC or more commonly ‘vinyl’] material. The earliest occurrences of this technology emerge from famous inventor and engineer Thomas Edison, Edison, who using the basic physics principles of how sound travels across a particular medium, developed a way to imprint or record the waves so that they could be played back or turned back into sound using a second needle - through what he called a 'phonograph'.1
The word phonograph essentially means sound-writer; the etymology is ‘phono’ [of or relating to sound or the voice; acoustic] - ‘graph’ [one who writes, delineates, or describes’]2. Essentially, the phonograph recorded and stored sound mechanically by etching the electrical signal of the sound waves with a needle, onto a tinfoil cylinder. Today, that technology has radically evolved from the gramophone, which shifted the medium to the more commonly recognized flat spinning disk which then set the path for electrically complex record players and vinyl manufacturing processes which are more focused on sound quality, frequency, balance, and output levels.
Record Players
Vinyl record players are electromagnetic devices that change sound vibrations into electrical signals. When a record spins, it creates sound vibrations that get converted into electrical signals - this is what can be called analogue [signals or data: represented by a continuously variable physical quantity, such as voltage, spatial position, etc.] recording of soundwaves. The phonograph, thought of as the grandfather of record players, had a brass cylinder wrapped in tinfoil, which rotated and moved lengthwise when turned by a hand crank. On one side was a diaphragm [a very thin membrane], connected to a needle; When sound waves were forced into the receiving end, it caused the membrane to vibrate and the needle to etch a groove into the foil as the cylinder was being turned by the crank, thus recording sound. A second needle and an amplifier were on the other side; When the cylinder was set to the beginning and the needle placed in the grooves, the original sound was reproduced as the vibrations were amplified.3 However, whilst the design of the gramophone and the recording process continued to evolve, the core elements from Edison of the 'needle in a groove' remained the same.
Today, A typical record player consists of a turntable, has a type of needle called a stylus, a cartridge, and an amplifier or speaker. All of these elements create a Transducer. A transducer is what changes mechanical energy into electrical energy and changes electrical energy into mechanical energy. The stylus, a tiny crystal of sapphire or diamond mounted at the very end of a lightweight metal bar like a needle, fits onto the end of an electromagnetic device called a cartridge, these may vary in function and style, but most significantly impact frequency response, channel separation, channel balance and output level.4 In an electrical cartridge, the metal bar presses against the crystal and each time it moves, it wobbles the crystal slightly, generating an electrical signal. These signals are fed out to the amplifier, which are the sounds you then hear. Some [cartridges] have tiny electrical coils and a magnet inside them so, when the stylus moves, it pushes the magnet up and down past the coil, generating electrical signals that are fed to the amplifier to create sound through your speakers - this model is closer to that of the original phonograph.
Vinyl Records
Records also called 'vinyl' or 'disks' are flat disks between 7-12 inches in diameter, each size plays at specific revolutions per minute [rpm], and each record has the unique imprint of the recorded material in the "grooves". The physical grooves on a classical vinyl record provide several cues about the audio track they contain. They "indicate where a track starts and ends, as the grooves in the lead-in and lead-out areas (before and after the track) are spaced much more loosely Additionally, grooves in louder parts of the track are larger and need more spacing than those in quiet parts; These features can be used to visually estimate the track’s structure" [check figure 3]5 The depths of each groove in a record represent the shape of the sound wave - the inverse of these grooves - ridges - are what is used to create a stamper. This is a metal sheet that is a ‘negative’ copy of the recorded material in order fashion records pressed onto soft polyvinyl chloride - this is what the consumer buys. Under an electron microscope, we can more clearly identify the shape of each groove, therefore sound wave - therefore the images of the waves seen in figures 1 and 2 are actually versions of grooves just in digital form.
Sometimes when listening to records, sounds that are not part of the music can occur and this 'crackling' phenomenon is “some of the sound distortions include collateral noise, crackle, and a muffled hum. This noise of the wax cylinder is the voice of the medium itself, audible media-archeological information (about the physically real event).” This anomaly is noticeable in the sound waves as shown in figure 4.4
Conclusion and Citations
Overall, Vinyl as a medium is important because of the significance of the material culture it leaves behind, but perhaps more importantly the way it physically represents and exhibits sound waves as material, malleable, and as ENERGY. We see how Vinyl allows us to map sound waves onto a material and then using a very similar process, reproduce the same sounds by transforming the energy of the waves.
1. Koenigsberg, Allen. Edison Cylinder Records, 1889-1912. New York: Stellar Productions, 1969. 2. Oxford English Dictionary 3. Roland Gelatt, The Fabulous Phonograph: From Tin Foil to High Fidelity. New York: Lippincott, 1955 4. Camlot, Jason. Phonopoetics: The Making of Early Literary Recordings. 1st ed., Stanford University Press, 2019. 5. Heller, Florian & Borchers, Jan. (2012). DiskPlay: In-track navigation on turntables.