What is the difference between digital and analog audio?
In: Technology
Analogue audio is stored in an analogue (continuous) medium such as vinyl or magnetic tape (audio cassette). Digital is stored in a discontinuous medium such as a CD or MP3.
Sound is a wave, so audio information just describes the shape of the wave. On vinyl there is a wavy groove which has that shape, on cassette there is a varying magnetisation of the tape which also has the shape.
~~On a CD the “height” of the wave at each moment in time is assigned a value from 0 to 255~~ *~~65535~~*~~. Then at the next timestep it has another value. So the true wave shape is approximated by a sort of stepped shape. See a comparison~~ [~~here~~](https://www.google.com/url?sa=i&url=https%3A%2F%2Fbeatlabacademy.com%2Funit%2Fmsd03-digital-analog-synthesizers%2Fasset-5-digitalanalog-waveform%2F&psig=AOvVaw3zWKdCV1GJ55rpplieYP3v&ust=1615291906233000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNj6-LjVoO8CFQAAAAAdAAAAABAD)~~.~~
*A digital signal on a CD stores the wave form as a series of values at moments in time, with those moments very close together. Think of a series of dots where if you squint you see the original curve. There are 65536 possible values, stored every 1/44100 seconds, which is all you need to replicate the original sound when you play it back.*
So long as there are enough values ~~and short enough timesteps~~ the digital shape is a close enough approximation to the true shape that no human can hear the difference. MP3 and other digital formats go further and compress the audio, so they sort of describe the shape rather than simply approximating it as outlined above. This can lead to distortions that humans can hear (or claim to).
You might think that analogue is therefore ‘perfect’ in a way that digital cannot be. This is sort of true, but any real analogue medium will have physical limitations which add their own distortions to the sound, potentially to a greater extent than good digital audio.
*Edit to add: yes I am aware that a digital signal perfectly replicates the waveform up to the desired frequency, thanks for all the reminders.*
*Edit 2: alright alright I get it. People have strong feelings about this analogy.*
*Edit 3: actually scrap that I stand by my statement that a digital audio signal is an approximation of the original. Sound is not band limited, and does not have finite bit depth.*
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