High Resolution Audio

Digital audio keeps getting better. So they say. Standard 16bit/44.1kHz audio is just barely good enough. And it is just good enough to cover a bandwidth from single digit frequencies to 22 kilohertz with a 96 decibel dynamic range. 16/44.1 exceeds the frequency range of unsullied young ears, and although short on the ear’s dynamic range, it’s plenty more than enough for the most dynamic music, which spans about 60 dB from softest to loudest. Even during the softest passages the music is at least 36 dB over the noise floor. High resolution formats go well beyond that by a good margin—20 bit adds another 24 dB of dynamic range, 24 bit takes it to 144 dB, more than the ear can handle. A 192 kHz sampling rate extends the frequency range out to 96 thousand cycles per second, more than two octaves above hearing range.

This begs the question of the purpose high resolution formats serve. The answer is interesting. At the end you’ll find a link to a long and thorough article on the subject. I’d suggest reading it when you have ample time to give it your full attention from start to finish and to allow some extra time to stop, contemplate, or reread a paragraph here and there. Until then, I’ll give you a few highlights.

The author, Monty, starts with a recap of how human hearing works.

“Thus, 20Hz – 20kHz is a generous range. It thoroughly covers the audible spectrum, an assertion backed by nearly a century of experimental data.”

This is an important place to start. Studies have not shown any need to playback frequencies beyond the range of audibility for realistic sound. He continues with some comments about “golden ears.” Then to the effects of ultrasonic frequencies on audio equipment.

“Neither audio transducers nor power amplifiers are free of distortion, and distortion tends to increase rapidly at the lowest and highest frequencies. If the same transducer reproduces ultrasonics along with audible content, any nonlinearity will shift some of the ultrasonic content down into the audible range as an uncontrolled spray of intermodulation distortion products covering the entire audible spectrum. Nonlinearity in a power amplifier will produce the same effect. The effect is very slight, but listening tests have confirmed that both effects can be audible.”

Most good amplifiers should be able to handle up to 50 kHz without much trouble, but most speaker transducers run into problems when fed very high frequencies. Either way, the speaker or the amp, inaudible ultrasonics can have a deleterious effect in the audible range.

“Sampling theory is often unintuitive without a signal processing background. It’s not surprising most people, even brilliant PhDs in other fields, routinely misunderstand it. It’s also not surprising many people don’t even realize they have it wrong.”

You want to start some heated arguments, just mention the Nyquist Theorem. The fact is you can’t hear digital sound, you never have and never will. The digital/analog converter takes the binary code and reconstructs a smooth analog waveform identical to the input that was sampled and converter into 1s and 0s.

“It might appear that a sampled signal represents higher frequency analog waveforms badly. Or, that as audio frequency increases, the sampled quality falls and frequency response falls off, or becomes sensitive to input phase. Looks are deceiving.

Sampling rates over 48kHz are irrelevant to high fidelity audio data, but they are internally essential to several modern digital audio techniques.”

It’s very important to distinguish between recording/processing/mastering side of digital and its playback. High sample rates are required for the former, not for the latter. Monty provides details.

“Understanding is where theory and reality meet. A matter is settled only when the two agree. Empirical evidence from listening tests backs up the assertion that 44.1kHz/16 bit provides highest-possible fidelity playback. There are numerous controlled tests confirming this.”

He cites one of the tests and provides links. Endless disputes about this issue will go on ad infinitum. Everyone’s entitled to their own opinion, but not their own facts. Nevertheless, fact denial persists.

“Not all papers agree completely with these results (and a few disagree in large part), so it’s easy to find minority opinions that appear to vindicate every imaginable conclusion. Regardless, the papers and links above are representative of the vast weight and breadth of the experimental record. No peer-reviewed paper that has stood the test of time disagrees substantially with these results. Controversy exists only within the consumer and enthusiast audiophile communities.”

This is how science works, and without science, you wouldn’t be reading this. Monty also carefully discusses the difficulties of testing procedures, confirmation bias and brain/sensory processing.

“The human brain is designed to notice patterns and differences, even where none exist. This tendency can’t just be turned off when a person is asked to make objective decisions; it’s completely subconscious. Nor can a bias be defeated by mere skepticism. Controlled experimentation shows that awareness of confirmation bias can increase rather than decreases the effect! A test that doesn’t carefully eliminate confirmation bias is worthless.”

Hence, double blind test protocol.

“I’ve run across a few articles and blog posts that declare the virtues of 24 bit or 96/192kHz by comparing a CD to an audio DVD (or SACD) of the ‘same’ recording. This comparison is invalid; the masters are usually different.”

Too often audiophiles are comparing apples to oranges. Sometimes they are hearing a real difference, but it has a cause other than the one they suppose. Redundancy makes a message more robust. They may be hearing a real difference. The cause, though, may not be the one they suppose.

“The point is enjoying the music, right? Modern playback fidelity is incomprehensibly better than the already excellent analog systems available a generation ago. . . .but bad mixes and encodings do bother me; they distract me from the music, and I’m probably not alone.”

Yes, yes, and yes you are not alone.

“Why push back against 24/192? Because it’s a solution to a problem that doesn’t exist, a business model based on willful ignorance and scamming people. The more that pseudoscience goes unchecked in the world at large, the harder it is for truth to overcome truthiness. . . even if this is a small and relatively insignificant example.”

Thanks, Monty. Here’s the link : [24/192 Music Downloads . . .and why they make no sense]