Don’t be fooled. 24-bit will not fix computer audio

Record producer Jimmy Iovine now chairman of Interscope and CEO of Beats by Dr Dre, says there are huge quality problems in the music industry. I listened to his talk during HP’s launch event for its TouchPad tablet and new smartphones.

“We’re trying to fix the degradation of music that the digital revolution has caused,” says Iovine. “Quality is being destroyed on a massive scale”.

So what has gone wrong? Iovine’s speech is short on technical detail, but he identifies several issues. First, he implies that 24-bit digital audio is necessary for good sound:

We record our music in 24-bit. The record industry downgrades that to 16-bit. Why? I don’t know. It’s not because they’re geniuses.

Second, he says that “the PC has become the de facto home stereo for young people” but that sound is an afterthought for most computer manufacturers. “No-one cares about sound”.

Finally, he says that HP working with, no surprise, his own company Beats by Dr Dre, has fixed the problem:

We have a million laptops with Beats audio in with HP … HP’s laptops, the Envy and the Pavilion, actually feel the way the music feels in the studio. I can tell you, that is the only PC in the world that can do that.

Beats Audio is in the Touchpad as well, hence Iovine’s appearance. “The Touchpad is a musical instrument” says Iovine.

I am a music and audio enthusiast and part of me wants to agree with Iovine. Part of me though finds the whole speech disgraceful.

Let’s start with the positive. It is true that the digital revolution has had mixed results for audio quality in the home. In general, convenience has won out over sound quality, and iPod docks are the new home stereo, compromised by little loudspeakers in plastic cabinets, usually with lossy-compressed audio files as the source.

Why then is Iovine’s speech disgraceful? Simply because it is disconnected from technical reality for no other reason than to market his product.

Iovine says he does not know why 24-bit files are downgraded to 16-bit. That is implausible. The first reason is historical. 16-bit audio was chosen for the CD format back in the eighties. The second reason is that there is an advantage in reducing the size of audio data, whether that is to fit more on a CD, or to reduce download time, bandwidth and storage on a PC or portable player.

But how much is the sound degraded when converted from 24-bit to 16-bit? PCM audio has a sampling rate as well as a bit-depth. CD or Redbook quality is 16-bit sampled at 44,100 Hz, usually abbreviated to 16/44. High resolution audio is usually 24/96 or even 24/192.

The question then: what are the limitations of 16/44 audio? We can be precise about this. Nyquist’s Theorem says that the 44,100 Hz sampling rate is enough to perfectly recapture a band-limited audio signal where the highest frequency is 22,500 Hz. Human hearing may extends to 20,000 Hz in ideal conditions, but few can hear much above 18,000 Hz and this diminishes with age.

Redbook audio also limits the dynamic range (difference between quietest and loudest passages) to 96dB.

In theory then it seems that 16/44 should be good enough for the limits of human hearing. Still, there are other factors which mean that what is achieved falls short of what is theoretically possible. Higher resolution formats might therefore sound better. But do they? See here for a previous article on the subject; I has also done a more recent test of my own. It is difficult to be definitive; but my view is that in ideal conditions the difference is subtle at best.

Now think of a PC or Tablet computer. The conditions are far from ideal. There is no room for a powerful amplifier, and any built-in speakers are tiny. Headphones partly solve this problem for personal listening, even more so when they are powered headphones such as the high-end ones marketed by Beats, but that has nothing to do with what is in the PC or tablet.

I am sure it is true that sound quality is a low priority for most laptop or PC vendors, but one of the reasons is that the technology behind digital audio converters is mature and even the cheap audio chipsets built into mass-market motherboards are unlikely to be the weak link in most computer audio setups.

The speakers built into a portable computer are most likely a bit hopeless – and it may well be that HPs are better than most – but that is easily overcome by plugging in powered speakers, or using an external digital to analog converter (DAC). Some of these use USB connections so that you can use them with any USB-equipped device.

Nevertheless, Iovine is correct that the industry has degraded audio. The reason is not 24-bit vs 16-bit, but poor sound engineering, especially the reduced dynamic range inflicted on us by the loudness wars.

The culprits: not the PC manufacturers as Iovine claims, but rather the record industry. Note that Iovine is chairman of a record company.

It breaks my heart to hear the obvious distortion in the loud passages during a magnificent performance such as Johnny Cash’s version of Trent Reznor’s Hurt. That is an engineering failure.

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25 thoughts on “Don’t be fooled. 24-bit will not fix computer audio

  1. Michael Grafl

    I agree with everything you say in your article, except calling the distortion in the recording of “Hurt” performed by Johnny Cash an engineering failure. I think it was an intentional artistic choice, and I’m fine with that, even if I would have done it differently. I do believe however that there’s a strangely wide gap nowadays between audiophiles and “normal” consumers who listen on their iPods that could be narrower. I think many people have no idea how good recorded music can sound, therefore there’s no interest in investing more than 30 bucks in a pair of cans.

  2. nancy

    Hello,

    It seems what HP includes in their computer implies more than just the 24bit thing. You can have a look in here:

    http://www.precentral.net/what-beats-audio

    Also, it seems the speakers included with their laptops do not often makes the difference, the difference is when you plug any audio device into the input jack.

  3. Tim Post author

    @nancy thanks for the link.

    The video does not even mention 24-bit which makes Iovine’s comments even more curious.

    Tim

  4. Foo

    > Nyquist’s Theorem says that the 44,100 Hz sampling rate is enough to perfectly recapture a band-limited audio signal where the highest frequency is 22,500 Hz.

    Um. No.

    Nyquist’s Theorem says that the largest frequency that can be represented, if poorly, by a sampling rate of N Hz is one of N/2 Hz. It does not say it can be represented well, nor does it say that any signal of frequency less than N/2 can be “perfectly recaptured”. Try “perfectly capturing” a sine wave of frequency 22,499.99 Hz on a CD some time.

      1. Alex Zuzin

        DACs aren’t functions, and have inherent limitations having to do with not being infinite. Treat yourself to a good review of downsampling, dithering and other basics of audio mastering, e.g. here: http://www.amazon.com/Mastering-Audio-Second-science-Book/dp/0240808371/ref=sr_1_1?ie=UTF8&qid=1298920935&sr=8-1.

        The difference between 24-bit/96Khz and 16-bit/44.1Khz is very clearly audible even on a poorly set up pair of near-field monitors in a very boomy room like my living room, and I’ve been playing in bands for some years (read: upper range hearing probably impaired a little bit :).

        1. Tim Post author

          Alex

          The difference between 24-bit/96Khz and 16-bit/44.1Khz is very clearly audible even on a poorly set up pair of near-field monitors in a very boomy room like my living room, and I’ve been playing in bands for some years (read: upper range hearing probably impaired a little bit)

          I don’t presume to say what you can and cannot hear; but the evidence as far as I am aware is that under controlled test conditions and with normal music signals the difference is hard (not necessarily impossible) to hear. Certainly that is what I have found from my own experiments, and I have worked long and hard at this.

          If you have some samples that show this “very clearly audible” difference please do post them and I will try them. I have active monitors; I have high-end headphones; I have a very respectable home audio system. I will find out if I can hear the difference when someone else is switching, or on a computer using ABX, and I will test with others in case my hearing is defective.

          I have done this with the samples here, for example, which are from a high-res advocate:

          http://soundkeeperrecordings.com/format.htm

          and not yet come up with a positive result.

          Nevertheless I do not argue that nobody can hear the difference. But where is the evidence that most people can, or that the difference is anything but subtle?

          Tim

  5. Martin Cohen

    I currently rip my CDs (legally bought) as 256k mp3s, the same as Amazon. Sounds good to me through my Sennheiser headphones. Don’t see any need for lossless. Then again, I’m over 50 and can’t hear much over 12,000 Hz.

  6. Innocent Bystander

    The Nyquist argument for CD perfection was debunked years ago. Here are some of the most obvious flaws in its logic.

    1. It assumes there is no signal above twice the sampling rate. Note I said “no signal”. It doesn’t matter if the hearer can hear the signal or not. If there is signal above 2*SR then the higher frequencies are aliased into the lower frequencies as strange unexpected sounds. To overcome this, you have to filter out the high frequencies. Unfortunately doing this means you have to start filtering well below the Nyquist frequency. So, basically, you lose high frequency detail.

    2. It assumes that the samples are infinite precision and error-free. Of course CD samples are only 16 bit and are not error-free. With 16 bits they have to compress the dynamic range to avoid obvious artifacts in the sound and you again lose detail.

    3. Strictly speaking the theorem only applies to signals that are repeated. However music is never exactly repeated so the theorem only applies approximately.

    Not to mention the problems with reconstitution of the signal etc.

    You also seem to be unaware why 16/44 was selected. This was the maximum sampling rate and precision that could fit on the CD technology of the time. Just like the horrible CGA screens of the original IBM PC were the best they could do for a reasonable price. In both cases, we can do much better now.

    1. Tim Post author

      @Innocent I don’t regard what you say as “debunking” but I certainly accept that what is theoretically possible is not achievable and said so in the piece above.

      However, you can easily supplement the theory with blind testing. Everyone is different, but in my own experiments I’ve found conversion of high-res signals to 16/44 pretty much transparent, ie the difference is inaudible as far as I can tell.

      Nevertheless, I certainly allow that there may be people and/or systems where this is not the case. My view though is that if there are audible differences they are subtle at normal home listening levels. Not something the average home listener needs to worry about.

      By contrast, differences in loudspeakers and room acoustics, for example, are very easy to hear. No argument about that.

      Tim

  7. Russ

    Nice piece Tim. But “The reason is not 24-bit vs 26-bit…” (3rd last par) should be “24-bit vs 16-bit”?

  8. Tom Davenport

    The article makes the right observations on how this is all coming from a headphone manufacturer. I wrote a similar article for Gizmodo last week, though I hasten to add my submitted headline referred to the marketing con rather than 24-bit being bad:

    http://gizmodo.com/#!5768446/why-24+bit-audio-will-be-bad-for-users

    In summary, 24-bit doesn’t matter to the majority consumers, which is why any forthcoming marketing campaign telling them it DOES matter will be a con. Forget whether you prefer 24-bit, or even have the money to build a room and system where it matters, this is about pointing out the marketing intentions. Maybe 24-bit marketplace will be a good thing for the industry, but for most consumers, it’s a con.

  9. Gary Gendel

    I’ve looked at what Beats Audio brings to the table. Although it is not up to audiophile standards it goes a long way to do things that should have been done a long time for consumer audio…

    1) It reduces EMI pickup into the analog path.
    2) It isolates the analog components from the digital ones reducing digital noise leaking into the audio.
    3) It adds a beefier amp with improved headroom.

    (1) and (2) significantly improve the SNR.
    (3) improves transient handling to prevent clipping.

    All of these can make a huge impact in the quality of the sound and are motherhood for any competent analog audio designer. It’s about time the industry put audio in seriously.

    As for 16 vs 24 bits, there are two factors at play here. They dynamic range and the level of change that can be detected by the human ear. Just because you find it doesn’t solve the first doesn’t mean it doesn’t solve the second.

    As for Nyquist, I agree with those that have already stated that theory doesn’t always get followed in reality. Frequencies above hearing can effect the sound in a number of ways. Filtering them out can cause significant phase shifts in the audible range. Even if you start a 3db/octave filtering at 100kHz there can still be a 1 degree phase shift introduced at 20kHz. In addition, there are harmonics caused by the interference of these that add richness to the sound that is lost if they are not faithfully reproduced. In the case of sampling at 44.1kHz, filtering is necessary because trying to reproduce them will cause all sorts of audible artifacts because they introduce high frequency content that did not exist in the original content.

    I worked as a developer of MPEG-1/2/4 video compression. What drives me crazy is that I can see compression artifacts that the average viewer doesn’t even notice until I point them out. The same is true for many trained ears in the audio field.

    I’m all for the work of HP and Apple to make things better. I don’t expect audiophile results with their devices because that’s not their market. However, having higher-quality captured means that I can actually enjoy this content in a high-fidelity setting without having to resort to “orphaned” technologies such as vinyl.

  10. Gislon

    Great discussion. Professionally I’ve helped introduce 320kbit streaming at BBC Radio 3 HD Sound (don’t worry I’ll get back to your main topic shortly). It’s only mp3 quality, but we’re suprised just how clear the difference is between 192 standard and 320 kbits ‘HD’. Most people could tell even on average headphones.

    For me, on my reasonable home sytem with dedicated PC sound card, the 16/44 v 24/192 differnce is just as clear and just as startling. Particuarly for classical music where ambience and timbre are an intrinsic part of the sound. The higher bit rate sounds more natural and relaxed – like real wood v veneer to get very silly about it.

    Try the comparison files here.

    I can’t find any rock and pop files to do a comparison with. But I’d guess the lack of real ambience on pop means you prob wouldn’t get much difference.

    1. Tim Post author

      @Gilson

      Did you try the comparison blind and carefully level matched? I know lots of people report high-res sounding better, but few controlled tests that confirm those reports. Which is odd.

      Tim

  11. George Bowles

    I do home recording, and when I switch over to 24-bit recording at 96khz, there’s definitely a noticeable difference, at least on sennheisers. less difference when playing, say, Autechre’s Oversteps in 24-bit style, through my laptop and into my mid-level receiver. but the difference is there, do the math. 3:2 bits, double the sampling rate. is there really any debate to be made? also computer processing and equipment will only continue to improve, so why not give the consumer the choice of mp3, flac, wav, or high definition audio.

    one good example would be to listen to how much better things sounds when watching a movie. the difference is there. it also depends on what type of music you are listening to and how it was captured, of course. acoustic sounds such as jazz will be most noticeable since they have more information to be captured.

  12. Tim Post author

    @George

    Thanks for the report. Did you test this with carefully level matched blind comparison? I like the Meyer-Moran idea of putting high-res output through 16-bit ADC – DAC and comparing it with the orginal.

    Of course for recording 24-bit absolutely makes sense because you may need to do some work on the recording before final output.

    Tim

  13. JFA

    My 2 pence about the sampling rate. Even if you can’t hear a pure tone over, says, 18kHz, the higher frequencies are useful for transient sounds: try on a square signal (OK it’s certainly not a sweet sound to hear), even if its fundamental frequency is low (1kHz or whatever), it carries very high frequencies due to its sharp edges, if you’re filtering it, its edges will be smoother… For a 1kHz square signal, 3 kHz “carries” ten time less power than the fundamental (-10dB) and at 9kHz 1 percent of the power… 96dB is 1/50 of the power…
    That said, I’m agree that the most significant impact on sound quality are due to by placement of loudspeaker in the room, room, quality of connections…

  14. Bill Henderson

    This is fascinating stuff. I read recently (can’t remember where) about a person who rips all their music to Apple Lossless knowing that they probably can’t tell the difference between that and 256kbps MP3 files. Their reasoning was weird, but I think I agree totally: Hard drive space is cheap and if you rip at the highest quality you are comfortable with – in this case, Apple Lossless – then you never worry about whether you have the BEST version to listen to. You can just enjoy the music, worry free. And isn’t that what it’s all about?

  15. Forestrial YopYow

    I find this discussion enlightening. However, this stemmed from talking about Beats Audio, and I still don’t know what is supposed to be so great about them. As far as I have been able to discern the only difference between a beats card and any other (hardware wise) would be the ferrite cores around the I/Os. I talked to HP’s techs for hours and could not get any further information about the bit depth/refresh rate of the cards themselves.

    If anyone has info regarding specs of Beats cards I would be very grateful.

  16. Edvin Karimi

    If you’re purchasing a laptop or tablet based on the internal speakers, then you should think about what it is you exactly want. Speakers truly are the last thing laptop developers think about because it’s a mobile device, not meant to be a Home Entertainment replacement. The cheapest desktop motherboard will have 24-bit / 96 audio hardware and drivers, if you need something better then you can go purchase an M-Audio 10/10 for $1,000 or an external M-box for $600, with the addition of expensive speakers and room acoustics.

    There is a HUGE difference between 16-bit and 24-bit, even in the ranges that you can not hear. My hearing falls off at 17khz (getting worse), however the difference between the two are still very noticeable. It’s like listening to an MP3 that was sampled at 192kbps against an MP3 that was sampled at 320+. It’s the clarity that makes the difference, not just the hearing range. However, this will not be noticeable when listening to any modern pop, rock, hip-hop or electronic music as they are so over compressed that clarity is lost in favor of the punch.

  17. the king

    Could be wrong but doesnt the ad da converters and the quality of the audio card itself contribute more to sound quality than the bit rate. Ive heard very expensiv e converters and they sound a world apart from other audio having thesame bit rate , if true its more logical to just have better quality digital processi g than worry about higher bit rate. Also 24 bit wont help much if the speakers are crap

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