The key difference between analog and digital technologies is that the first records waveforms as they are, while the second converts analog waveforms into sets of numbers, recording the numbers instead. When played back, the numbers are converted into a voltage stream that approximates the original wave.
Analog technology brought us Chuck Berry, Elvis, and The Beatles on vinyl records, 8-tracks, and cassettes. Using today’s digital devices, original studio recordings can be cleaned up, re-mastered, and distributed as digital files that sound better than those long playing records (LPs) ever did. While tapes and LPs wear out with use, a digital recording sounds exactly the same no matter how many times it’s played. It’s also easily copied and moved between storage devices.
It might seem counter-intuitive that a technology that converts an analog waveform to numbers would sound better than one that records the waveform as it is, but digital technology accomplishes this feat through sampling. When a waveform like music is recorded with a digital recorder, the music is sampled several thousand times per second. For a CD-quality recording, the average sampling rate is 44,000 times per second. That’s 44,000 numbers stored for each second of music. The higher the sampling rate, the more accurate the recording, though there comes a point of diminishing returns considering the file grows larger while the human ear ceases to be able to hear a difference past a certain point. When the device plays the digital file back, the waveform is reconstructed, one bit at a time at lightening speed.
You might compare digital technology to drawing a cartoon on the bottom edge of a notepad, slightly changing the drawing on each successive page. If you repeat the drawing all the way through the pad, then flip the pages, the figure appears to be moving smoothly in whatever way you drew it. It might walk across the page, sneeze, bend over, or run. In the same way, the digital device plays back the numbers so quickly that the samplings combine to “redraw” the analog waveform in its original form.
When buying digital music online, some people choose a lower sampling rate for smaller files. When playing MP3 music on a handheld device or an inexpensive portable player, it might be hard to tell the difference between music sampled at 44,000 times per second and music sampled at lower rates. However, when playing the files on a decent car stereo, home stereo, or surround sound system, the loss of quality will be more noticeable.