What is the difference between digital and analog audio?
In: Technology
I think it’s useful to understand the context of why you are asking, as there’s something that I think the other answers, which are technically correct, miss. The sound you HEAR is a waveform, always. The device producing the sound waves is “Analog” depending on your specific definition of the word and the context.
Most of the time this stems from some argument or need to figure which is “best” digital or Analog.
If we accept that sound waves can be represented by a 2d graph that plots the sound pressure exerted on your eardrum, this is an anlog of that sound wave. If we are talking recording formats, the term Analog has a more literal meaning as well especially in the bygone age of physical media.
A vinyl record, like an LP, is a literal, physical analog of the original sound wave. In the groove there are tiny peaks and troughs that that match what the sound wave looks like on that 2d graph of the pressure exerted on your ear drum. It’s reproduced by a needle tracing over the physical groove. An amplifier takes the signal from the needle and increases the sound pressure, amplifying the signal. It’s possible to do this on purely mechanical level, I.E gramophones, or using electricity. In an electrical system of amplification, the needle is connected to a device that creates a very small voltage when you move it up and down. A speaker that you hear sound from typically requires a great deal more voltage than the needle devices generates, so the amplifiers job in this case is to increase the voltage of the signal from the needle. A speaker is usually considered “Analog because of the kind of device it is. It is an arrangement of electromagnets that moves the core based on the input voltage. The cone of the speaker is attached to the core of the magnet and produces a sound wave by the cone moving air. The input signal is a constantly variable electrical signal that is faithfully and directly reproduced by the movement of the core. This wave is always sinusoidal in nature.
What you hear from the speaker is a sound wave that closely resembles the wave that the records physical “Analog” was originated from. In the case of an electrical system like I just described, if you measured the voltage over time at the needle using an oscilloscope you’d see a weak electrical signal, but it would be very similar to the peaks and troughs as the original record. If you then measured the same voltage over time at speaker, it’s again a very similar wave as the needle one, and the record one, u this time with a much higher voltage.
All sounds simple right? The reason I said SIMILAR wave and not SAME wave is that at each point in the process, noise is introduced. When the record was made, some noise is inherent in the process of doing that. When the needle devices changes the up down movement to voltage there is noise induced into the signal. When the amplifier takes the sound and increases the voltage, more noise is introduced.
I’m going to skip over tapes a medium, but the brief story there is that a tape is an analogue of an original wave that uses magnetisim rather than a physical representation as found in a vinyl record.
So then along comes “digital” processing. Digital equipment doesn’t deal with variable state. This is because it’s what is known as solid state. Different voltages mean very little to solid state devices. It knows only ON or OFF Not going into that here, but that’s where this term come from. In operation, you know the device is either on or off. Speakers are really the opposite of “solid state”, in operation they might be any almost infinitely variable. They need a voltage that is constantly variable, to produce a reproduction of the original recording.
If you store something digitally, at a fundamental level it is all just 1 or 0 in terms of value. The difficulty is, if you want to store a signal that is a constantly variable wave and then reproduce it on a speaker that needs a sinusoidal wave to produce sound, with devices that only know 1 and 0.
Well, let’s deal with storing the wave first. A microphone is basically like the needle on the record but in reverse. It’s a diaphragm attached to a similar device that when you speak to it, it creates voltage. This gives you the original, electrical Analog of the sound wave you want to store. What you do with your digital device is sample the voltage value of the wave produced by the microphone at specific, repeatable points in time. This is referred to as sampling rate. When you do this, you can imagine you don’t get a smooth sinusoidal curve, you actually get something resembling a load of steps, but if you trace a line through the centre of each step, you get something that approximates the original wave. The more samples you have, the smaller the steps are and the closer you’ll be to the original. The disadvantage of higher sampling rates is the much higher volume of numbers you need to store. You might be familiar with the files that store sound waves this way this way. They are called .WAV files, and they usually take up a lot of disc space on your devices. The devices that perform this conversion are called Analog to Digital converters.
Now you want to take your stored wave and play it back on your speakers. You need to take this wave approximation, that is basically what voltage the speaker needs to see at a specific point in time to produce the wave, and convert into the actual voltage the speakers need to work. This is done by a digital to analog converter.
In a typical digital music storage system, there’s usually an intermediate format, whare the wave is stored in a more compressed format, that introduces some loss of the original wave, with the benefit being that the file takes up less space on disc. This would be an MP3 file or similar. Now with streaming media what’s more important is how long that file takes to download to your device. No streaming service will give you WAV files directly, or even the more modern FLAC format which typically requires less space but doesn’t lose any of the wave. Your getting an AIFF, an MP3 or an OGG. The specifics of this are not so important, but the reality is that by converting from a WAV or FLAC some of the original wave is lost. This happens if you use a streaming service, or if you are dinosaur that still does MP3 files.
Let’s break down where some of the perceived issues occur in this set of transactions that make up a digital music system. There is both loss of original fidelity and noise in recording the sound picked up by the microphone when it is stored. When it it becomes compressed so that it can actually be used, either for streaming or stored on a device for playback, you lose yet more of the original wave. When you playback the file, there will be noise and sometimes further loss induced by the DAC.
So,
If you been following along, you might be thinking, Analog is surely best then, less steps, closer to the original wave” this is not always true.
All Analog systems are susceptible to noise. This can have a serious impact on how good both the recording and the reproduction sound. Many billions have been spent trying too eliminate noise from these systems. It continues, as you must still have a microphone and a speaker to record and reproduce sound. (I’ll use reproduce, as you can to some extent eliminate the mic with modern music production where a great deal of the sounds you hear might be generated digitally.)
Digital systems don’t have an issue with noise. And the “loss” of fidelity induced by compression doesn’t really have an impact on how you experience the sound. All sound waves have elements that the ear can’t actually hear, but when you record the wave, it is stored anyway. Formats like MP3 and ogg are extremely good at getting rid of the bits of the wave that your ear wouldn’t be able to hear, even the system reproduced it effectively. There is also the advantage of digital signal processing, which is a process of eliminating noise, and dinner times effects that make the sound better using software. It’s only possible to do this in a digital system. It’s cheaper and more effective than what is possible in Analog systems.
It’s also worth considering transmission of an audio signal, A digital signal, whether it’s DAB radio transmission, Bluetooth or the HDMI signal from your games console won’t get noise induced into it. It’ll work, or it won’t. It won’t be better some days than others or deafen you cos you put your phone too close to it, or because you’ve got a bad connection or anything else. You don’t have to eliminate noise to repeat it between multiple locations. It can even self heal if something does go wrong during transmission using a technique known as error correction.
Because the difference isn’t really important. Both are a part of a system. What you hear is “Analog”. You can’t avoid that. These days it’s almost impossible to consume audio without some kind of digital technology, somewhere in the process, and that’s overall a good thing that has made the experience better, not worse.
Latest Answers