What is the difference between digital and analog audio?

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What is the difference between digital and analog audio?

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Anonymous 0 Comments

Analog is wavy air, and can be stored as wavy grooves. Digital is 1s and 0s. When you want to listen to digital audio, it gets turned into wavy air again first so you can hear it.

Anonymous 0 Comments

Analog audio is a continous wave, digital it’s like taking little pictures of the wave, that make it discrete. But there is too much pictures so in most cases you can barely notice the difference.

Anonymous 0 Comments

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.*

Anonymous 0 Comments

I guess you mean analog and digital recording of audio.

Sound is vibration of air (or any medium it travels through). Its properties are frequency (how many oscilations it makes in a second, i.e. how high the tone is) and amplitude (how ‘big’ are those oscilations, i.e. how loud it is).

So, how to record that? In essence, there are three ways: vinyl records, magnetic tapes and digital.

Vinyl is the simplest one. Imagine a big membrane that is in the way of those vibration. From the air, the vibrating transfers to the membrane. Now connect a sharp needle to it so it vibrates too. And while vibrating, that needle leaves the marks on a rotating dics. Then you can go reverse and the needle follows the grooves on the record, vibrate, transfer vibrations to the membrane and then to the air so we hear the recorded sound. Sure, this is oversimplified but it shows the important part.

Tapes work similarly, but the membrane is not connected to a needle but to an electromagnet. Magnets and elecrticity have a love relationship. When a magnet moves near the wire coil it creates electricity in in. And vice versa, if there is electricity in a coil, the magnet will move. So, as the magnet vibrates it creates a small amount of electric current that magnetizes the small particles of iron oxide on a moving tape. What was a wiggly scratch on a vinyl is now a series of variating little magnets of different strengths. You play the tape by reverting the process: tiny magnets on tape create the electricity in the electromagnet in the tape-player head, which moves the magnet connected to the membrane which creates the sound.

Both these systems transfer physical properties of sound into some other physical properties – depth and width of scratch mark on the vinyl or strength of magnets on tape.

Now the digital recording… which also goes from the membrane and into electromagnet to transform the vibration into electric current but then that current get measured and stored as a number.

As the sound is vibration that changes many times a second (it goes from 16 to 20000 oscilations per second) it has to do quite a lot of these measurements and store a number for each one. For CD it is 44.1 thousand per second, film standard is 48000 and, more often than not, initial recording in profesional environment is 96000 times per second.

Difference between this and the previous two ways is that now we don’t have one physical property transfered into other but into a series of descrete numbers somewhere in memory of the computer.

To store them permanently, you can enrave them into silver foil (CDs and DVDs) or use magnetic disks (hard drives).

Magnetic disks use the same mechanism as the audio tapes but they don’t record the vibrations directly but the numbers created according to those vibrations. So what’s the benefit?

(edited this paragraph as it was badly formulated) Magnetic tapes and disks are losing a tiny portion of quality with every reading/listening. Here is the important difference. If you copy analog data from the tape, there will be more and more shhhhhh noise introduced in every new generation of a copy as the electricity makes noise. But the copying of a digital recording is immune to that as each new reading and copying gives the same series of numbers as the original even if the recording is faded or partly damaged. That is because even as the magnetic material wears off, reading of the numbers is the same and when you deal with numbers you have safety mechanisms to check if your reading is ok or even to recalculate a part that is missing (see checksums for more info on this). But eventually the hard disk will fail.

Anonymous 0 Comments

OK, here’s a really ELI5:

Sound travels in waves. Tie a jump rope to a fence and wave it up and down; the shape of the rope will resemble a sound wave. Now imagine you could freeze time, and you wanted to build a copy of the rope’s shape, but you only had bricks.

So, you take your bricks, and start to stack them up under the rope. Some times you’ll only need a couple of bricks; sometimes you may need to pile them up 10 or 12 high to touch the rope. After a while, if you step back a bit from your work, you can see how the piles of bricks look *very much*, but not exactly, the shape of the rope.

The rope is the “analog” wave form, while the bricks are the “digital representation”. The analog wave is *continuous* – the rope’s height above the ground can have any value between, say 2 inches and 4 feet. The digital representation is *discrete* – it can only be 1, 2, 3, 4, etc. number of bricks. It can’t be 3.867 bricks.

Analog systems capture the continuous wave. The groove in a record – do 5 year olds even know what those are anymore? – is a long continuous wiggle that copies the original sound wave. This is actually fairly simple to do – the first records were made of wax, with the platter rotating while a needle, driven by a microphone, made the groove on the surface. This is an analog to analog process.

Digital systems try to recreate the original wave by using standard sized pieces to fill in the space beneath the wave, just as we did with the rope. But how wide, and how tall, should each of these pieces be?

This is beyond ELI5, but there was a smart guy named Nyquist who figured out that to completely capture all the information in the original wave, it needs to be sampled at twice its highest frequency. This tells us how “wide” the bricks need to be. For example, if the highest frequency in the wave was 4000 cycles per second, then we would need 8000 samples, so our ‘bricks’ have to be 1/8000 of a second wide.

The height of the bricks are is a function of how many digital bits in each brick. If you use 8 bits, you can get 2^8 = 256 levels. If you use 16, you get 2^16 = 65,336 levels. If you use more bits, it makes the bricks less high, so you can squeeze the brick piles closer to the actual wave, and so sound more like the original.

Note the digital process requires an analog-to-digital conversion at the input, and then a digital-to-~~audio~~analog conversion at the output. There are some – Neil Young comes to mind – who believe that this distorts and ruins the original recording; others don’t notice it.

finally, and this is way beyond ELI5, digital techniques like Adaptive-predictive Pulse Code Modulation (ADPCM), use clever math and engineering tricks to get the sound even closer to the original, while using less bandwidth.

EDIT: Thanks for all the kind comments and awards. Thanks also to those who corrected the minor errors, and expanded on some of the stuff I left out.

EDIT EDIT: To all the longitudinal wave fans. yes, you’re right. So am I. A sound wave can be represented as a two-dimensional signal on an oscilloscope, and it was that representation I was referring to. I elided the silly scope reference because it’s ELI5.

Anonymous 0 Comments

The most essential difference is in the ability to copy it. Analog is like copying a drawn picture, at each copy it deteriorates a bit, but you can get (in theory) the most minuscule details in there. Digital is like copying a written text, an E stays an E, or it changes in something entirely different (like an F). You can keep making a copy of the written text with no loss of information, unlike a picture.

Anonymous 0 Comments

There are some incorrect explanations in the comments here. [A digital signal has the same resolution as the analog to digital converter originally encodes](https://youtu.be/pWjdWCePgvA?t=635). There is no data loss due to “stepping” or “discreteness” of the digital signal.

That video is somewhat technical but has an accurate explanation of the differences- and surprising similarities- between digital and analog signals.

Anonymous 0 Comments

Analog = Recorded by Physics (Analagous)

– Scratching sound waves into a record
– Recording sound impact on magnetic tape
– Real film photographs
– Can be done without electricity
– The recording happens by physics directly effecting a recording medium. The playback happens be the recorded medium effecting some kind of amplified replay device like a speaker. The record is an atomic level, mimicking shadow of a real event.

Digital = A recreation of physics through instructions. Usually numbers. (digits)

– CD, Youtube, MP3 audio
– Digital photos. Not vectors.
– Requires some kind of processor. Usually a micro chip. But can be other mechanics.
– Player pianos that use paper rolls or music boxes that use a music spindle.
– There are 2 processes: encoding and decoding. Encoding takes real world physics and records it to numbers. Decoding “plays back” the numbers to create physics.

Anonymous 0 Comments

Here is electronic music pioneer Wendy Carlos on the different between digital and analog audio:

” Digital, of course, is essentially computer data which accurately describes an audio signal. It’s easily manipulated and can be copied exactly — all those ones and zeros, you know. Analog is how we usually describe sound waves, a continuous change of pressure or an electrical signal, what a microphone produces, what we used to record on tape. It’s a much riskier way to handle audio, but historically was the method we first discovered.

Between the two, don’t look for deeper meaning or arbitrary differences. There is a cult of near-religious dogma that proclaims analog sound on LPs (“vinyl”) to be perfection (what a hoot that is for those of us who used to cut LPs for a living!). They think you have to use special wires and elaborate techniques they don’t even understand, and they claim that digital is in cahoots with Lucifer. It’s kind of pathetic, based on ignorance and flamboyant cheek. The simple answer for synthesizers or reproduction is: To the listener, it shouldn’t matter at all, as long as it sounds fine. If you’re a performer, it shouldn’t matter at all. If you have a very advanced analog synthesizer and then you have another that is all digital–and you get a lot out of both–fine, use them.

On the other hand, digital can, in principle, let you be more precise, with finer finesse and control. Analog runs out at five significant digits of accuracy (it doesn’t have infinite resolution), something like that, and there’s tape hiss to contend with. If you want to put the money and time into it, you can obsess with digital until you’re dead. It’s a potential that hasn’t often been tapped, but usually you reach a practical limit, there’s life for you. Microtonal tunings are a breeze with digital synthesizers, but very hard to do with analog.”

From: [http://www.wendycarlos.com/intvw01.html](http://www.wendycarlos.com/intvw01.html)

Anonymous 0 Comments

Analog stores the waves themselves, and converts waves on a vinyl record into waves of voltage/current to your speaker.

Digital stores waves as numbers (bits), where the height of the highest point on the highest wave is the biggest number, and the the total amount of numbers per second represents the highest frequency you record.

Then processors read the bits and convert it to voltage/current outputs to your speaker.

So the difference is in how you store it, as you get the same result from both (there are slight differences, and professionals might have to look at their requirements in detail)