At best you'd think, “My TV doesn't display UV or IR so it won't make any difference since I can't see those frequencies anyway.” At worst you'd be concerned about getting a sunburn or a heat rash.
Now imagine I said, “You should listen to my special audio version of Miles Davis's Kind of Blue because I re-encoded it from the masters with special ultrasonic data and that totally makes it sound better!”
At best you'd think, “My amplifier filters out inaudible sounds so it won't make any difference.” At worst you might even worry what pumping all this extra audio data into your speakers could do to them.
The thing is, this second example isn't hypothetical. What I've described above is happening right now as companies like Neil Young's Pono are telling people that audio files encoded at a bit-depth of 24-bits or a sample rate of 192kHz sound better than the 16-bit, 44.1kHz versions of the same audio on playback (recording is different, and we'll get to that later).
This difference between 16-bit/44.1kHz audio and anything greater than that has been tested (a lot… in double-blind tests) and we have yet to find any human that can reliably notice that difference. Bit depths greater than 16 bits and sample rates above 44.1kHz simply don't matter as long as the data is converted properly (and the industry's ability to do that conversion has improved substantially since those very first CDs were released at the dawn of the digital music era, though most of us at home don't have the skill or setup to convert and downsample properly).
Bit Depth and Sample Rate Explained
A digital audio file's bit depth determines its dynamic range (the difference between the softest portion and the loudest portion). 16 bits gives us 96 decibels (dB) of range. 24 bits give us 144dB. As per the aforementioned double-blind testing that's been done no human can hear that difference.
The sample rate of an audio file determines the frequency range that can be reproduced. Nyquist-Shannon sampling theorem informs us that perfect fidelity reproduction is possible with a sample rate equal to twice the maximum frequency we wish to reproduce. This means a 44.1kHz sample rate can reproduce frequencies up to 22.05kHz. Most human children can hear from about 20Hz up to about 20kHz. As we age the high end of that number narrows very quickly. Again, double-blind testing confirms all of this.
Science Prevails Over Emotion
There's a lot of science behind what we're discussing here. Nyquist's theorem has been proven by others many times over (hence the reason that many others' names are often attached to it). If this article instills in you the need to reconfirm all of this on your own (and you'd be in the good company of this author and several recording-industry professionals if it does) the only way to do it is to utilize a tool that allows you to perform your own double-blind testing (ABXtester, available for free for both iOS and Mac, works great). Without double-blind testing you (and I!) are quite subject to confirmation bias. Our minds are not objective when we have too much information.
There's also a ton of pseudoscience here. Earlier this month at CES I had Bruce Botnick, the producer of The Doors' LA Woman, tell me that after listening to a 24-bit album he feels better than he does after listening to the same album at 16-bit. That's great for him, folks, but doesn't mean much to rest of us. Also, Bruce is busy working with Neil Young to convince us all to buy their 24-bit Pono player, and I'm sure Bruce feels better after each Pono pre-order, too.
The truth is there is the potential to store more data in a 24-bit/192kHz file than in a 16-bit/44.1kHz file. You can see it if you just compare the two – the former will be many times larger than the latter. If you were playing this to a dog, for example, that creature might well be able to tell the difference (because dogs can typically hear higher frequencies than humans, so it makes sense to use a higher sample rate for music targeted towards audiophile dogs). If you're like me and will be playing your music for humans, though, we haven't yet evolved our ears where anything above 16-bit/44.1kHz matters upon playback. That's why it was standardized for compact discs at the beginning of the digital audio era, and that's why it still works today.
Music is Emotional, and That's a Good Thing
Music isn't just a listening experience. Music is also very much an emotional experience. If you believe your speakers are better than your friend's speakers, you're going to be happier listening to music at home. There's nothing wrong with that. I might like the band Weather Report (I do); my wife might hate them (she does). It's simply personal preference and we're both right.
Similarly, if you've convinced yourself that 24-bit or 192kHz (or both) sound better you are quite likely to believe you hear a difference when listening to music in that format. There's nothing inherently wrong with doing something solely because it makes you happy to do it. Just don't confuse that for science; and please don't try to convince others with pseudoscience. That's the last thing we, as a people, need.
Next, head to page 2 where we address the recording process, mastering, why Pono is great, iTunes and more.
Page 2 – The Recording Process
Now that we've addressed playback, I want to speak quite positively about using 24-bit during the recording process. When capturing music, especially music that's going to be mixed and mastered and produced after-the-fact, it makes good sense to record far more data than you will need in the end. The reason is that the mixing process very deliberately removes data. If you want to hear more guitar the reality is there is no more guitar than what you recorded, so you're therefore going to remove some of everything else to make the guitar more prominent. At this point it's great to have more data than you'll need because you can take out plenty and still be left with a very high-quality sample. Record at 24-bit, mix at 24-bit and then convert your final mix to 16-bit with good quality digital signal processors (DSP) and all will be well.
Mastering Matters
The Pono player isn't the first time we've seen higher-resolution-than-needed audio peddled to the public as having better sound. The failed SACD movement was based on this despite the fact that a lot of those SACDs did sound better than their predecessors. This was not because they were released at higher resolution, rather it was because the music was remastered and reconverted when making those SACDs. Even a minor volume increase will be near-universally received as “sounding better,” and a lot of that remastering involved boosting the overall levels.
There was more to it than that, though. We came from a vinyl-targeted world, where the higher frequncies needed to be boosted to sound good on most consumer-grade record players. When we took those same masters and simply burned them to CD, they sounded different (I'll leave the subjective good vs. bad out of it).
It took the industry time to learn what works best in a digital world and then to develop the DSPs and other techniques and technology required to bring it to fruition. Then as soon as they did everyone started compressing music down to 128kbps MP3s and none of it mattered, at least not for a while.
Thank Goodness for Pono
While it's true the Pono folks are doing audiophiles and consumers a disservice using pseudoscience to sell their player, Pono is based on a great mission: let's all start caring about high-quality music again. Pono does a lot of things right, including being sure to play back digital files with no modifications. Even though the Pono player is capable of 24-bit playback, it plays back 16-bit files with no upsampling. Pono's mission of “playing music as the artist intended it” is noble. Maybe they should re-focus their marketing on that.
Mastered for iTunes
Apple is doing something interesting with their “Mastered for iTunes” program, but even more interesting than that is Apple requires everyone to send in 24-bit files for conversion to AAC. This means Apple is stockpiling music at the highest level. Again, this is very smart: when you know you're going to have to throw out data, it's good to start with more than you need in the end.
This also means that if Apple were ever to decide that all iTunes songs should be released as Apple Lossless files (which, unsurprisingly, Apple sets at 16-bit/44.1kHz), they have a lot of that data on-hand, ready to convert and release. That's smart, too. (For some “between the lines” reading, take a look at Apple's Mastered for iTunes PDF. They're clearly prepared for the future here).
Here again it's worth doing some double-blind testing just to hear the differences (or lack thereof) between lossless to the current form of compressed audio. Take a file that you've ripped from CD at Apple Lossless and then convert that to 256kbps AAC and test yourself. I have yet to find a track where I can reliably hear the difference on any audio gear I have. That includes testing classical and jazz recordings where the subtleties really come through. I'm certain there are differences there, I just can't hear them on anything I have tested (though it's quite noticeable at 128kbps and below).
In The End, It's What You Prefer
My advice to casual listeners and even audiophiles is to set up a listening environment that sounds good to you (speakers, amplifiers, DAC, headphones). From there as long as you're playing AAC 256kbps files (or better), you're likely to be quite happy if you can get over the math. There will possibly be some tracks where you can hear a difference between AAC 256kbps and lossless, but the way most music is produced it probably won't matter much.
For anyone who cares: Other than the A/B testing of digital tracks, this entire article was written while listening to vinyl. All my records are in good shape, and I have a new belt and needle on my Technics SL-B210 turntable in my office, but it still sounds a lot worse than even the worst CD I can find. Pops, crackles and wow & flutter mean I'd have to spend many thousands of dollars to upgrade my hardware (and likely vinyl) to get anywhere close to CD quality. But it is fun flipping records and reading liner notes.