All music is beautiful
~Billy Strayhorn

I apologize to everyone who looked for my article earlier today. I was delayed in writing it last night. I think I need to start working ahead and building a buffer.

sunstreetreviews asks

Audiophile friends tell me that vinyl records have a much richer sound than MP3 files. Is that really the case, and if so, why?

In principle, there’s no reason a digital file should produce lower-quality sound than a vinyl record. In reality, tests are inconclusive. Why this is the case has to do with how sound works, and how sound is stored on a computer file.

Some Sound About Sound

Sound is a wave of pressure in the air. The frequency of the wave determines the pitch. Let’s unpack this statement. Imagine that I hold a string between my two hands, and I move my hands so that the string wiggles. This is very analogous to sound. In fact, the wiggling of strings on string instruments is what causes the sound they make. The more wiggles on the string, the higher the pitch of the “note.”

As more complicated sound is made (for instance if I speak), the strength of the pressure changes to control the volume and make a pattern (like a word). The result looks something like this:

The combination waves like this is called beating. In a real song, there will be many notes at once, and the note will change as the song goes on, so the change of the higher-frequency wiggles will change.

Sampling

Now that we understand a little bit about how sound works, we can talk about how it’s stored on a computer. Because the computer can only hold a finite amount of information, some of the waveform is necessarily lost. The computer keeps track of the strength of the pressure at evenly spaced points in time. The computer also doesn’t have perfect ability to keep track of the strength of the pressure of the wave at any given time. It estimates the pressure. How good the estimation is is called the resolution. The number of times the computer measures the strength of the pressure wave is the sampling rate.

Vinyl Records

Sound is recorded on a vinyl record by copying the shape of the sound wave onto a groove on the record. The shape of the groove mimics the shape of the pressure wave, just like the plots I’ve shown you above. The resolution is given by the recording device’s precision when it cuts the groove. Our machines aren’t perfect and our recording devices aren’t perfectly precise. Similarly, the sampling rate is determined by the width of the needle that cuts the groove. The needle tip cuts a groove the same width as the tip, and we lose all information about how things change under the needle. So, the wider the needle, the  lower the sampling rate. (I am glossing over some details, many of which I don’t understand.)

This is a bit surprising. We don’t usually think of our world as “discrete” or “digital” in the same way that computer information is. Whether or not space itself has this property is open to debate. However, on a larger scale our world is made of atoms, and these are the “pixels” of the universe.

The Comparison

A vinyl record has a very good resolution and a very high sampling rate. It would take up a lot of computer memory to get the same sound quality. However, we ourselves can only hear so well. Once the sampling rate is high enough, and the resolution good enough, we can’t tell the difference if the sampling rate is higher or the resolution is better.

Furthermore, the human ear hears some notes better than others. By not recording those notes, we can reduce the size of an audio file without any obvious change in audio quality.

“Lossless” audio formats, like .wav, use a high enough sampling rate and a good enough resolution, that we can’t tell the difference from a vinyl record. However, to conserve space on hard drives, we often compromise between audio quality and memory usage. “Lossy” audio formats, like .mp3 use various tricks, like the one described above, to reduce the file size. In the end, whether or not a digital file has a lower-quality sound than a vinyl record depends on the person who produced the file. For more information, see Gregor Robinson’s comment below. Thanks for the correction, Gregor.

Further Reading

Skeptoid has an article discussing the comparison between vinyl records and digital files.