Is high-resolution audio really as good as it sounds?
By Ian Paul, TechHiveApr 2, 2014 3:30 am PDT
Singer-songwriter Neil Young is on a crusade to save recorded music with a new digital audio player called Pono aimed at offering so-called high-resolution digital audio. PonoMusic, the company behind the player, recently started a Kickstarter campaign, with the promise that a finished version will start shipping in October.
Called the PonoPlayer, the device is supposed to feature high-quality digital-to-analog conversion technology. The device pairs with a digital music download store loaded with high-resolution audio files in the FLAC lossless format. This is no MP3 player: Pono promises better quality sound than what you get from the files you buy from iTunes and Amazon—and in some cases, even the few CDs left sitting on your shelf.
When Young first began talking about Pono publicly back in 2012, the recording legend told late night host David Letterman that Pono plays music that is “as close as digital can get to analog [sound].”
Analog recordings such as vinyl and tape have long been considered the “gold standard” for sound quality among audiophiles. High-resolution audio achieves this supposed high quality by offering music files encoded with 24-bit depth and a sample rate of 192 kHz (24/192) as well as other ranges including 24/96.
If you believe the hype, all that extra aural bandwidth means you will hear classic Springsteen, Dylan, and Fitzgerald as if they were playing on a classic hi-fi system.
What Pono promises
Many products and services have tried to popularize the notion of high-resolution audio. So far, none have been able to attract much more than a niche audience. Pono, however, may have an advantage over previous attempts, thanks to the star power of Neil Young and the Pono ecosystem that replicates the early iTunes-iPod experience.
“There’s never been music of this quality, with this level of convenience,” says John Hamm, PonoMusic CEO. “That’s really the Pono strategy.”
As of this writing, Pono’s Kickstarter campaign has raised more than $5 million from more than 15,000 backers.
But achieving that supposedly top-notch audio means more than just opting for Pono or another high-resolution audio source such as HDTracks.com; you’ll also need to buy all of your favorite recordings all over again in new high-resolution versions. And that will mean shelling out more money for new music files upgraded to high-res audio that, in the case of Pono at least, will cost between $15 and $25 per album. In contrast, a copy of the Frozen soundtrack costs $12 to download on iTunes; many of the other top-selling albums on iTunes cost $10 or less.
Overhauling your music library can be an expensive proposition. But at least the improved quality you’ll enjoy in return will be worth it, right?
Not really, says Christopher “Monty” Montgomery, a digital audio engineer who heads the non-profit Xiph.org Foundation that’s responsible for the Opus, Ogg Vorbis, and FLAC digital audio codecs. There may be problems with digital audio, Montgomery contends, but high-resolution 24/192 audio doesn’t solve any of them.
Instead, Montgomery says, when you buy into high-resolution audio, all you end up with is a healthy dose of pseudoscience and bigger hard drive requirements for storing files that can be up to six times larger than what you get on a CD.
The problem with high-resolution audio? To put it bluntly: you can’t hear the difference between high-resolution audio and a CD.
Sample rates, bit depth, and bit rates
The components of digital audio can be broken down into three basic categories—sample rates, bit depth, and bit rates. Let’s start with sample rates, which are measured in kilohertz (kHz). High-resolution audio’s sample rate is generally between 96 kHz and 192 kHz or higher whereas CDs are sampled at 44.1 kHz.
Imagine a sound wave continuously fluctuating through space. To turn that wave into a digital file, you have to grab parts, or samples, of that original wave and store them in digital form.
To capture the human audible sound wave—that is, the sound you and I can actually hear—all you have to do is make sure the sample rate is a little more than double the highest frequency in the original performance. This will accurately capture the entire audible sound wave in digital form, according to the Nyquist-Shannon sampling theorem, the basic principle governing how digital audio recording works.
The next consideration for digital music is depth, or the number of computer bits that you have to capture your audio. The more bits, the greater dynamic range of soft to loud sounds that your audio file can have. There are basically two audio depth measures in use today: 16 and 24 bit. CDs are traditionally produced as 16 bit, while 24 bit sound files are typically used by audio engineers during recording and production.
The final piece of the puzzle—bit rates—are the most widely quoted figure when talking about compressed audio files such as MP3s, AAC, and Ogg Vorbis. Apple, for example, touts its iTunes Match service for upgrading your music files to a bit rate of 256kbps. All this means is that to store one second of audio, a file uses 256 kilobits or 256,000 bits of data. The bigger the bit rate, the bigger the file—and, presumably, the better the sound quality.
But there’s one little snag in all of this talk of juiced-up audio: the human ear. The maximum frequency the human ear can perceive is widely accepted to be 20 kHz. Based on what we know about sample rates, that means to get your ear to perceive 20 kHz, you have to produce an audio file with a sample rate slightly greater than twice that amount.
And that’s where you hit problems, Montgomery says, since 192 kHz audio contains sound frequencies that are several times greater than our capacity to hear.
Dan Lavry, founder of Lavry Engineering, a company specializing in analog-to-digital and digital-to-analog converters, agrees. “The misconception about 192KHz is due to the intuition that more is better…There are many situations where more is better, but sampling [is not one of them],” he said.
In 2007, the Journal of the Audio Engineering Society published a study conducted by members of the Boston Audio Society which sought to determine if listeners could tell the difference between CD-quality and high-resolution recordings (DVD-A and SACD recordings, at the time). The study took 60 subjects and conducted 554 listening trials. During the trials people were asked to identify if they were hearing a CD or a high-resolution recording. In the end, the listeners were only able to identify the high-resolution recording 49.82 percent of the time, suggesting the subjects were guessing rather than making an informed choice.
Worth it or not?
So if distinguishing between high-resolution and regular CD recordings is difficult, is there value to purchasing a high- resolution recording? Hamm contends there is. “We’ve had hundreds and hundreds of people of all ages listen to music on Pono,” Hamm said. “We are absolutely comfortable that the vast majority of those people have a much more satisfying and gratifying experience by listening to music in 24/96 and 24/192.”
But Montgomery counters that even a properly encoded MP3 can satisfy most listeners. And while other audio experts we talked to wouldn’t go as far as Montgomery, many are dubious about the added quality of high-resolution audio.
Nevertheless, there could still be value to high-resolution audio, and the Boston Audio Society study offers a clue as to why. Toward the end of the paper, the authors suggest that sound engineers often put more care and attention into higher-resolution recordings than they do to mass market CD releases.
Dr. Sean Olive, President of the Audio Engineering Society and Director of Acoustic Research for Harman international, agrees. “I’ve heard some wonderful CDs, but I’ve also heard some wonderful 24/96 files,” Olive said. “I really think the difference is how well they’re recorded and mastered.”
So you may in fact get a higher quality experience from select high-resolution recordings. But that has more to do with how the master file was produced than anything else.
That’s not to say there aren’t problems with the current state of digital recordings, though. Poorly encoded MP3s, low-quality recording equipment, and the fight for pop music producers to create the loudest music possible—the so-called loudness war—can all play into a subpar listening experience.
As for your music files, FLAC recordings (whether 24/192 or CD quality 16/44.1) may well be worth it, and the Pono music store won’t require you to own a Pono device to purchase music.
But there’s no guarantee those high-priced digital tracks will be worth your time. Especially when you can often get the same quality at home by purchasing an audio CD and ripping it into a lossless format like the Apple Lossless Codec (ALAC) using iTunes.