Analog audio

Analog recording (Greek, ana is "according to" and logos "relationship") is a technique used for the recording of analog signals which, among many possibilities, allows analog audio and analog video for later playback.

Analog recording methods store signals as a continuous signal in or on the media. The signal may be stored as a physical texture on a phonograph record, or a fluctuation in the field strength of a magnetic recording. This is different from digital recording which digital signals are represented as discrete numbers.

The Phonograph was the first machine used to capture analog sound, and was invented by the well-known inventor Thomas Edison in 1877. Edison incorporated various elements into his Phonograph that would become staples that can be found in recording devices to this day.

For a sound to be recorded by the Phonograph, it has to go through three distinct steps. First, the sound enters a cone-shaped component of the device, called the microphone diaphragm. That sound causes the microphone diaphragm, which is connected to a small metal needle, to vibrate. The needle then vibrates in the same way, causing its sharp tip to etch a distinctive groove into a cylinder, which was made out of tinfoil.

In order to playback the sound recorded on one of the tinfoil cylinders, the recording process is essentially reversed. As the cylinder spins, the needle follows the groove created by the previous recording session. This causes the needle to vibrate, and then the diaphragm. This vibration comes out of the diaphragm, which is now functioning as a sort of sound amplification device, much like the bell on any wind instrument. The result is an audible reproduction of the originally recorded sound.

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Wikipedia