Yes, the High-Res Difference Is Audible

Would you like to feed your audio system with signals equivalent to what the artist, producer, and mixing engineer heard in the studio? For most people, this is a no-brainer. Why would you not want to hear what the pros heard? And on that basis, a new generation of music players, USB DACs, and other high-resolution audio products is now on the market, seeking open ears and open minds. You'd think this would be cause for celebration. But a small cadre of rigid ideologues are not celebrating. They're insisting that there is no audible difference between CD-quality audio and high-res audio. They bought Perfect Sound Forever, the ancient Compact Disc marketing slogan, hook, line and sinker. Infinitely condescending, the Perfect Sound Foreverists claim to have science on their side and dismiss any other point of view. But the latest science flatly contradicts their long-held dogma.

For non-techies who just wandered into this war of ideologies, CD audio is a 16-bit, 44.1 kHz format. That means a string of 16 zeroes and ones is transmitted 44,100 times per second. High-res audio is generally meant to refer to 24-bit, 88.2 kHz (and up) formats. The theory is that a longer string of bits, transmitted at a higher rate, translates into higher quality. In practice, to my ears, sometimes the difference is audible and sometimes it's not. A lot depends on the character of the original content, the resolution of the files used for mastering, and the quality of the mastering job. But I've heard enough great-sounding high-res audio—some demos staged by manufacturers, some by myself at home—to be pretty certain this new world is worth exploring. So it would be a shame if the Perfect Sound Foreverists succeeded in undermining high-res audio just as it's reaching a new generation of potential audiophiles.

And that is just what they are trying, perversely, to do. I once published a blog asserting that CD Quality Is Not High-Res Audio. A typical Perfect Sound Foreverist responded: "This is the assumption of all too many audio dilettantes who do not understand the engineering and physics supporting digital audio in general and the CD Redbook specification in particular. In fact, the evidence does not support the contention that there is an audible difference between CD and the so-called 'high resolution' audio formats, which differ from CD by using longer word sizes and sampling rates than CD."

The evidence cited over and over in favor of the Perfect Sound Foreverist viewpoint is a study by E. Brad Meyer and David R. Moran presented to the Audio Engineering Society in 2007. The title is Audibility of a CD-Standard A/DA/A Loop Inserted into High-Resolution Audio Playback. The abstract says: "Claims both published and anecdotal are regularly made for audibly superior sound quality for two-channel audio encoded with longer word lengths and/or at higher sampling rates than the 16-bit/44.1-kHz CD standard. The authors report on a series of double-blind tests comparing the analog output of high-resolution players playing high-resolution recordings with the same signal passed through a 16-bit/44.1-kHz 'bottleneck.' The tests were conducted for over a year using different systems and a variety of subjects. The systems included expensive professional monitors and one high-end system with electrostatic loudspeakers and expensive components and cables. The subjects included professional recording engineers, students in a university recording program, and dedicated audiophiles. The test results show that the CD-quality A/D/A loop was undetectable at normal-to-loud listening levels, by any of the subjects, on any of the playback systems. The noise of the CD-quality loop was audible only at very elevated levels." While access to the study is paywalled for non-AES members, you can buy it for $20 here.

Seven years later, a new study was submitted to AES by Helen M. Jackson, Michael D. Capp, and J. Robert Stuart, all of whom are associated with Meridian Audio Ltd. in the U.K. The title is The Audibility of Typical Digital Audio Filters in a High-Fidelity Playback System. The abstract says: "This paper describes listening tests investigating the audibility of various filters applied in high-resolution wideband digital playback systems. Discrimination between filtered and unfiltered signals was compared directly in the same subjects using a double-blind psychophysical test. Filter responses tested were representative of anti-alias filters used in A/D (analog-to-digital) converters or mastering processes. Further tests probed the audibility of 16-bit quantization with or without a rectangular dither. Results suggest that listeners are sensitive to the small signal alterations introduced by these filters and quantization. Two main conclusions are offered: first, there exist audible signals that cannot be encoded transparently by a standard CD; and second, an audio chain used for such experiments must be capable of high-fidelity reproduction." (Emphasis added.) Twenty bucks will get you a look at the study here.

So here are two studies undertaken with double-blind methodology, which the Perfect Sound Foreverists (and objectivists in general) insist is the scientific gold standard. They say a double-blind study is always right; they slam anything else as "pseudo-science." What could go wrong? Yet these two double-blind studies contradict one another. Only one of them can be right. But which one?

We might drill deeper into the details and discuss the different hardware, content, listeners, and testing practices. One aspect of the newer study that I find interesting is the Training section. I probably can't quote the paywalled material at length but I'll summarize. Jackson, Capp, and Stuart believed, based on preliminary data and feedback, that listeners needed time to prepare themselves for the task. So they implemented a three-phase training program that allowed listeners to familiarize themselves with the 200-second piece of music used for comparison, the filtering used in the test to distinguish CD-quality audio from high-res audio, and the test conditions. Only when listeners had prepared themselves in this manner did the actual testing move forward.

The conclusions? Listeners could hear the difference between 16/44.1 and 24/192. The filters and quantization used to downsample high-res masters for CD release can have a "deleterious effect." However, not all music reveals this loss of transparency. It is more audible with music having prominent echoes. This is roughly consistent with my considerably less scientific high-res listening experience: Sometimes I can hear the difference, sometimes I can't. Jackson, Capp, and Stuart also caution that, to ensure meaningful results, psychophysical tests should "minimise cognitive load," which presumably was the intent of their training procedure.

The new study is a win for high-res audiophiles. But it probably won't silence toxic ideologies. Nor will it be sufficient in itself to ensure the success of high-res content and equipment. The future of high-res audio is in the hands of artists, recording engineers, product designers, marketers, and enthusiasts. It's great that they now have a more compelling story to counter the rigidity, dogmatism, bitterness, and condescension of the Perfect Sound Foreverists. But they will also have to produce both compelling high-res content and the gear necessary to make it sing. And then current and future audiophiles will have to decide for themselves whether high-res audio is worth the investment. In the end, this battle is not about science. It's about music. Anything that brings you closer to music is a good thing. And having a virtual seat in the recording studio, hearing what the artist intended, is a great place to start.

Audio Editor Mark Fleischmann is the author of Practical Home Theater: A Guide to Video and Audio Systems. It is now in its 14th print edition and first Kindle edition.

mastemaybe's picture

I suppose 4k being "sometimes visually superior to 1080 on 50" TV's @ 12 feet" is next?

Sony says so (actually, lol, Sony already recognizes and has stipulated the very real limits of 4k resolution)...but I digress.

So a company that constructs $100,000 loudspeakers and $20,000 DVD players is involved/connected with a "study" that indicates higher resolution media is "sometimes" audibly superior to a CD? Shocker, there. Further humor: there's just ONE double-blind asserting the contrary? Maybe one in the last 3 months, anyway.

All on a site with no less than 23 advertisements for gear on their home page with a vested interest in it selling.

Guess I'll remain one of the dunderheads who has simply failed to discern the difference- not sometimes, but ALL the time- and has ignorantly left more cash in my wallet for the purchase of innately inferior media.

So then there's an upside, lol.

Ladyfingers's picture

The study, as you describe it, confirms the audibility of certain filters, not the innate audibility of different sample rates/bit depth.

hk2000's picture

I'm sorry, Even if it were to be true, The price of admission into that club is just too steep and not worth the reward. People with the means to invest in it will probably do whether they can hear the difference or not. If given the choice to listen to a CD recorded w/o any compression at 16/44.1 on a $1000 system or a commercially produced copy of the same CD with compression and processing at the production stage in 24/192 on a $100,000 system, I would choose the first w/o hesitation. Its all in the source media. As an EE, I KNOW there is no audible difference, as a philosopher, I admit there is a real and undisputed difference in the perception of the listener who spent a fortune on audio equipment BELIEVING it will sound better.

Rich67's picture

In this test I agree that the filters were tested and not the sampling rate. The more cogent issue is that most of the benefits claimed by the High Res literature is elimination of artifacts that are outside of the human range of hearing or so far below the noise floor as to be inaudible. Nothing electronic will ever give you the feeling of live music. Save your money on buying overhyped electronics and use the money to buy tickets to live concerts or go to many of the small clubs featuring your local musicians. Support the musicians rather than electronics manufacturers.

Old Ben's picture

In theory, I could see hi-res audio making a difference. Even if some frequencies that are capturable in hi-res are not audible to the human ear, sounds in such frequencies could interact with other frequencies (audible or inaudible) to produce audible sounds.
For me the issue is cost of admission. How much money do I have to spend to maybe hear a difference. I have a PS3, a Dolby HD/DTS-MA receiver, but a relatively inexpensive 5.1 surround setup. I honestly don't know that I can tell the difference between audio of a DVD vs. the audio for a Blu Ray. I suspect that if I spent a grand or two on better speakers, I would perhaps hear a difference, but that's a big expense for a maybe. The same thing goes with hi-res audio. It's a lot of money (expensive player, expensive speakers/headphones, and relatively expensive media) for something that MAY sound better.
I think that for hi-res to really take off, the demonstration opportunities need to improve. Stores like Best Buy need to have A/B tests set up where people can hear the difference between CD sound and hi-res sound. It needs to be easier to try different media players, different headphones, different speakers, etc.

mwelters's picture

I'm willing to allow that a difference is noticeable given the right equipment and a well-trained ear. For the vast majority of music listeners, listening on lower price-point home stereo or theater equipment, or on portable players, the increase in quality will be lost. Hi-res audio will remain a niche market. It increases neither convenience nor, in any clear way to average listeners in real world situations, quality.

Otherwise, I agree with the other commentators. Its not clear that this second study disproves the first.

An analogy can be made with movies. Blu-ray is clearly superior than any streaming video I've seen, and uncompressed DTS-MA or Dolby TrueHD is amazing compared to Dolby Digital or Dolby Digital Plus on streaming videos. Nonetheless, the vast majority of viewers don't really see or care about the difference, hence how rare disc rental places have become (Redbox being a last refuge). There is a point beyond which the majority simply does not see a worthwhile improvement. With hi-res audio, the difference is much less obvious than it is in the streaming video analogy, so hi-res audio just doesn't stand a chance outside of a niche market. Indeed, I'm still coming to grips with the shift to streaming (which the studios seem to be promoting by allowing streaming weeks or months before it permits a movie to show up at Redbox; a good way to eliminate the physical market) and the loss of quality it (currently) entails.

Ladyfingers's picture

Even assuming there was a slight difference - audible only to expertly-trained listeners - is that really worth 10 times the space/bandwidth requirements of 16/44.1 and re-buying albums? I'd rather have albums remastered without brickwalled mastering than a higher resolution version of the same audio.

vqworks's picture

Mark, I actually share some of your obvious frustration with the "Perfect Sound Foreverists" and my own listening experience tells me that the 20Hz to 20 kHz audible range, as determined by the objective crowd, falls at least somewhat short. I agree with Old Ben about audible and inaudible frequencies intermodulating to create audible beat frequencies, which can alter the sense of timbre.

Unfortunately, the newest experiment doesn't give us ample support because it's done by affiliates of a manufacturer of high-end equipment. This raises more than a few eyebrows.

In fact, aside from the hard argument that the objective group makes about the audible frequency range, I think they have most things right. Over the years, to many rave reviews of audiophile products were not validated with published specs and measurements. So manufacturers can more freely make virtually any claim.

And, yes, the experiment was really more of an assessment of filtering.

Even more serious to me is the fact that we have a lot of new and re-issued source material that can't even allow us to experience any benefit of higher bit and sampling rates. I'm talking about source material that has been mastered with severe limiting or "remastered" old material that's been put through the same process. You certainly wouldn't hear the potential dynamic range of your system (or even on a Red Book CD) with that source material.

Forgetting about sampling rates for a moment, we now even have dynamically limited new material mastered digitally pressed on audiophile vinyl.

Even if you were listening to great source material on a high resolution system, you can only fully appreciate it if your listening room is as quiet as an isolation chamber.

While I know that you don't need to spend a fortune to be able to purchase a high-resolution system, most consumers simply don't care. With such a fragmented electronics market, there are too many different products competing for consumer dollars (phones, tablets, game consoles, etc.), so consumers choose cheap low-resolution downloads for audio played on their phones or tablets through cheap earbuds, Bluetooth speakers or docking stations. They don't watch Blu-rays like we do, either; they stream through Netflix, Hulu, or Amazon or just settle for DVDs. It is really, really sad but also really, really true. They don't care. In fact, they'll go out of their way for the lower end stuff.

Audiophiles make up a niche market.

Yuri Korzunov's picture

Difference between both bit-depths depend on not only bits number.

Correctly compare whole playback system:
audio player software + driver + DAC + speakers + listening room.

deckeda's picture

You say the difference is audible but cite a flawed manufacturer's study as evidence. That's odd, because if something is audible, it just "is" period, and no study or test can either prove nor disclaim it.

That knocks out anyone's assertions to the contrary. If I like something better, it IS better, for ME, end of story. By the same token, people who don't value better sound to the extent they won't pay the extra hard disk storage fee for example are placing THEIR values on me as they neatly sum up "for everyone" why it's not worth it. And I'm not interested in what anyone else thinks.

Except the EE above, who by nature of his profession (his words) knows what's audible or not, no listening actually necessary. Yeah, I really want to know more insights from that genius.

Yuri Korzunov's picture

High resolution important for restoring audio data in audible range.

Often Kotelnikov/Nyquist theorem interpreted without its restrictions. The theorem applied for infinite signals. Musical signals isn't infinite.

Of course, if no real advantages by high-res audio (as you say - for you), no sense use it in home applications. In music production workflow we can't without high-resolution today. It allow improve end-user 16bit/44kHz resolution quality.

High resolution audio is not only marketing product, but it next stage of progress in audio technologies.

Yuri Korzunov's picture

Sorry, my last post addressed to deckeda.

Lord_Oxford's picture

I listen though a Asus Xonar Essence ST (PCI card), a small T-amp and decent, small monitors at near and medium field, in a small-ish room.

The improved smoothness with hi-res on instruments like violin and small, muted brass is anything but subtle.

I hardly ever wince like I do with 16/44 transfers.

This has nothing to do with ultrasonic bandwidth and everything to do with time-domain coherent filtering that preserves timbre within the audio band, and anyone can hear it, even if their aural faculties don't work much above 8-10 KHz.

Unfortunately, the same luddites/zealots who used to assure us that lossy-encoded files were indistinghishable from the 16/44.1 PCM (this 10 or more years ago, when digital bandwidth and storage were actually relevant considerations) have moved on to claiming that hi-res is also indistinghisable from 16/44.1 PCM.

These tin-eared philistines infuriate me - THEY are the ones putting obstacles in the path of progress, not the "audiophiles" they sneeringly refer to.