Many audio aficionados split into two camps, those supporting modern digital audio, and those supporting vinyl records.

by Brian Dunning

Filed under General Science

Skeptoid Podcast #303

March 27, 2012

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https://skeptoid.com/audio/skeptoid-4303.mp3

For as long as there have been competing standards — horses versus steam, paper versus parchment, Android versus iPhones, Whigs versus Tories — fanatics have taken sides and promoted them as superior with nearly religious passion. The comparison of sound quality between vinyl records and digital recordings stands tall among these platform debates. Nearly all audio enthusiasts take one side or the other, some openly and with zeal, most with subtlety and qualifying their preference through acknowledgements of the pros and cons of each. Either way, one basic question supersedes either preference: Does it make any detectable difference?

Again, those full of zeal, on both sides, assert that the difference is detectable, implying that they would be able to tell. In a few moments we'll take a look at some of the testing that has been done to study this claim. But first, a quick overview of the salient technical points.

The principal difference is the nature of the storage medium, which is either analog or digital; a smooth-flowing waveform as cut into the grooves of a vinyl record, or digital representation of the recorded sound with numeric amplitudes sampled at a high frequency. There's an exquisite elegance to the way that a stereo signal — two discreet, simultaneous channels of music — can be encoded into a single groove that one needle follows. As the groove moves side to side, a single channel is produced, with its frequency determined by the speed at which the needle is pushed left and right, and its amplitude determined by how far it's pushed. To add a second channel, we bring in a second axis of movement: vertical in addition to horizontal. Tip them both over at 45°, and we have a groove that varies in depth as well as in its horizontal axis. How fast and how far the needle vibrates down to the left describes the signal in the left channel; how fast and how far the needle vibrates down to the right describes the signal in the right channel. Adding the two signals together produces the instructions for how the groove is to be cut; at every instant, there is one smoothly flowing waveform describing the left channel, and a second describing the right channel. It's a beautiful system.

A digital audio recording is defined by two basic parameters: the sample rate, which is how many times per second the height of the waveform is sampled; and the resolution, which is the number of possible levels that can be measured at each sample. For a compact disc, this resolution is 16-bit, when means that the height of the waveform is measured, at each step, on a scale of 0 to 65,535, which is very precise. This measurement is performed at a sample rate of 44,100 times per second. This number is chosen because it's just over twice the highest frequency that the best human ears can hear, which is around 20,000 Hertz. A formula called the Nyquist rate shows that this is the minimum sample rate needed to produce the full range of human hearing. Lay each word of sixteen zeros or ones end to end, double it because there is a separate measurement for each stereo channel, stream them past at 44,100 measurements per second, and the speed at which those bits go by is called the bit rate. The higher your bit rate, the higher resolution and sample rate can be used. If this stream is to be recorded on a compact disc, it goes through another conversion to change it into a completely different series of ones and zeros that can be more accurately read by the laser. If it's stored on a computer, it can be algorithmically compressed via any of a number of different schemes, producing tradeoffs between file size and preservation of data.

So there our battle lines are drawn. There are myriad things one could say in addition to each. Vinyl and digital both have good points and bad points. But here's the reason why the entire debate is stupid: whether the music is stored on vinyl or a CD is just not that important a part of the overall system. It's like deciding which of two different cars is best by comparing their spark plug wires. There are many, many variables in the process of playing recorded music that noticeably affect the sound, from the microphones, to the mixing, to the mastering, to the quality of the playback hardware, the amplifier, and (far and away most important) the quality of the speakers and characteristics of the listening room; whether the recording was vinyl or CD is simply not one of these important variables, with apologies to the zealots. Both methods are easily far superior to any differences the human ear might hope to distinguish.

A lot of vinyl proponents say that the difference is subjective, for example that it sounds warmer or just better. Digital proponents tend to point out objective difference, such as the fact that a digital signal can accommodate a higher dynamic range, which is the difference in loudness between the quietest and loudest parts of the recording. But can they actually tell the difference under controlled conditions?

Well, unfortunately, this is a bit like asking which race car driver is most talented if you put them into identical cars. That car would always suit one driver's style and preferred setup better than the other. Finding an identical recording on vinyl and on CD to compare doesn't really exist. In the early days of CDs, record companies sometimes didn't bother making new masters of the old recordings; they used the same masters that had been used to press the vinyl. The results were CDs that sounded tinny or thin. The master suited vinyl, not digital. Now mastering engineers will almost always make a new master designed for the intended medium. A master is a special mix designed by an engineer who knows who's going to be listening, how they're going to listen, what other music it needs to sound good against, and so on. The separate instrument tracks might be individually equalized, spread across the stereo spectrum, or have a dozen other parameters applied. Thus, a CD and a vinyl pressing of the exact same recorded performance are likely to be very different. If they're not, that means an inappropriate master was used for one or the other, and the test will be biased.

Moreover, the vinyl playback method includes giveaways: clicks and pops, hissing, and other noise produced by the mechanical playback experience. Indeed, much of what's often lauded about vinyl recordings — such as the "richer, warmer" sound — is not a result of accurate reproduction, so much as it is an artifact of the playback mechanism itself.

It's a hard science fact that digital is capable of reproducing higher frequencies than vinyl, above the range of what most people can hear. But, can people distinguish whether a piece of music contains those frequencies or not? According to research performed at Japan's NHK Laboratories in 2004, the answer seems to be no. They took 36 people and ran 20 tests with each. Only a single 18-year-old girl was able to beat random chance, and so they retested her separately, but the effect disappeared. Nevertheless, the researchers issued a somewhat qualified conclusion that they could "neither confirm nor deny the possibility that some subjects could discriminate between musical sounds with and without very high frequency components." Whether that recording is vinyl or digital, any frequencies it may or may not have above 20,000 Hz make no difference.

Controversy also exists between various digital formats, lending credibility to the whole format war concept. Two high end consumer digital formats, Super Audio CD and DVD Audio (technically Direct Stream Digital and Pulse Code Modulation), have been bantered back and forth by industry experts. But in 2004, a paper presented at the 116th Audio Engineering Society conference in Berlin found that:

...No significant differences could be heard between DSD and high-resolution PCM (24-bit / 176.4 kHz) even with the best equipment, under optimal listening conditions, and with test subjects who had varied listening experience and various ways of focusing on what they hear. Consequently it could be proposed that neither of these systems has a scientific basis for claiming audible superiority over the other. This reality should put a halt to the disputation being carried on by the various PR departments concerned.

In 2000, some excellent research was published in the Bulletin of the Council for Research in Music Education where subjects listened to digital and analog recordings of the same concert performance, recorded unequalized and unmixed especially for this test. They were able to switch back and forth between the two at will, and everything was blinded and well controlled. Overall, the digital version was preferred in all ten scoring areas. However the recording media for this test were compact disc and cassette tape, so it's not directly comparable to a vinyl record. The researchers concluded:

Results showed that music major listeners rated the digital versions of live concert recordings higher in quality than corresponding analog versions. Participants gave significantly higher ratings to the digital presentations in bass, treble, and overall quality, as well as separation of the instruments/voices. Higher rating means for the digital versions were generally consistent across loudspeaker and headphone listening conditions and the four types of performance media.

To summarize the science, digital is the superior reproduction format, but analog (particularly vinyl) offers a particular type of sound that some people prefer. I liken it to a Ferrari versus a Mustang. They may have different metrics, but the people who like them for what they are don't care so much about that.

The best argument in favor of vinyl recordings need not be bolstered by unsupported claims about the technical quality of the recording, and that's the physical, tangible experience. Lowering a needle onto a record engraved with an actual audio waveform is comparable to building your own hot rod with greasy hands and case hardened tools. Its performance compared to that of a factory produced BMW is simply not relevant. It's about an experience, not about metrics or tabulated results. More senses are involved: the smell of the album cover, the touch of lowering the tone arm into the groove, the sight of the stroboscope indicating the precise turntable speed. It's a full experience to which the listener must dedicate focused attention and time. Vinyl records are a hands-on, personal connection to the actual audio, and that's something no amount of digital perfection can replicate. You can debate the validity of that connection all you want, and you'll find that it's a metaphysical, philosophical issue. There is no logic or practical connection. But some things, these types of connections — those for which no practical, quantitative explanation exists — are sometimes the most important.



By Brian Dunning

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