Have you ever seen this displayed on a CD or a vinyl record?
“This is a pure digital recording”
Well let’s stop right there. First you must realize that a digital recording can be converted to analog for playback on vinyl, and that an analog recording can be converted to digital so it can be played back on a CD.
There is a lot of conversion from analog to digital and digital to analog that can occur in the process of recording and playback. So it really depends on where you begin the process as to whether it qualifies as a pure digital recording. This is because the instruments generating the sound are still analog instruments, the transmittal of the sound from the instrument to the microphone still travels through the air in vibrations (air pressure pulses), and the microphone itself still “hears” analog vibrations which it converts into an analog electrical impulse.
The digital process begins at the point where the electrical impulses generated by the microphone are encoded onto a recording device. In the case of digital encoding, the first thing that must happen is to convert the analog electrical impulse into a digital code that represents the analog signal. It is from this point, called the “Analog to Digital Conversion”, that the basic underlying debate really begins.
In order to “digitize” an analog signal, engineers developed a method of describing a sound wave’s attributes (frequency, loudness, waveform, etc) into a numerical code, a unique code for each particular “sample” taken. Keep in mind that the description is done for a particular moment in time, so if you have sufficient samples per second, and if your description is highly accurate then when played back this string of samples will sound very much like the original analog sound that it attempts to represent.
A good analogy always helps to visualize this process…
When you look at a picture on a TV you see a picture which looks a lot like the original. But when you put your nose right up to the display you see the pixels that collectively represent the picture.
The more pixels used, the more accurate the description is. In the case of a moving subject, the more frames per second, the more realistic and accurate the movement looks. In the audio digital world this is analogous to the sample size and the sample rate. As you can understand, the more accurate the descriptions are, and the more of these descriptions per second that are provided yield an image that will more closely represent the original analog signal, but it can never fully represent the analog signal because you can always improve on either the description or its frequency.
So why is digital so compelling if it cannot quite achieve 100% accuracy? The answer is that once a sound is digitized, the remaining process can be largely free of the problems that accompany analog recording and playback.