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Thread: Is the dynamic range of CD sufficient?

  1. #21
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    While a discussion of math is all good, I also think it would be good to support robust investigations of how 16 bit, 44.1k compares to higher resolution music in actual controlled listening environments. While many are critical of the Meyer & Moran study, the best way to respond to it is with a study at least as robust.

    Mark Waldrep appears to be trying to organize such a test per comments here: http://www.realhd-audio.com/?p=2147

    Supporting Mark's efforts to conduct a robust test (financially, equipment loans, ears, etc) seems like a good thing to clarify under what conditions 16 bit 44.1k playback sounds better/the same/worse than higher resolution music (if that's his goal if I read his comments accurately). I think everyone wins if such a robust test is conducted because we all learn something from it, regardless of where people stand without such a test.

  2. #22
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    Quote Originally Posted by Sonus View Post
    Well, first my room has a 24db noise floor. I know people with 20DB noise floor rooms.
    A live Symphony can cross 120db easily for short period of times (in big venus).

    120db-20db=100db vs the 96DB of a CD.

    BTW:
    The dynamic range of human hearing is roughly 140 dB, in my opinion this is the DR value we should strive for.
    It seemed by the Ken Rockwell quote above, the de facto range of CD is about 100db...? Plus, the key is what is the recording venue noisefloor...with an orchestra of 80 people, I doubt its 20db.
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  3. #23
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    Just some empirical data from a 24 bit digital recording. Done with a small number of microphones, and minimal processing. 88 khz/24 bit.

    I found a quiet passage without music. Not a digital zero, and may have been only electronics other than mikes feeding it for that period. Though I doubt it.

    Grabbing 100,000 samples at this quietest point, L 388 samples and R 585 samples below -120 db. I doubt anyone can put together a real system more than that at the speakers. L 4235 samples and R 8209 samples below -96 db. L 8900 samples and R 18,008 samples below -90 db. This really is not much out of 100,000 samples. Peak levels were in the mid -50 db range with the average around -68 or -69 db.

    Same recording, in a quieter portion with music, in this case solo cello I grabbed 350,000 samples. L 35 samples and R 30 samples below -120 db. L 580 samples and R 473 samples below -96 db. Or about 1.5 samples below -96 db every 1000 samples. None of these samples were contiguous. Would you hear that differently if all samples below -96db were dithered and brought up to -96 db ? I don't know, but I find it doubtful. I also would think the difference even if audible is going to be really, really small.

    I also grabbed an area with several instruments playing, but among the quietest areas with that. Out of 100,000 samples 2 in each channel were right at -120 db. and L 20 samples R 26 samples were below -96 db.

    In one of the more energetic regions I grabbed 200,000 samples. None were as low as -120 db. L 26 samples and R 15 samples were below -96 db. Peak levels were L -5.6 db and R -6.2db. And this a recording of acoustic instruments in a quiet hall, not a rock recording by any means. Only about 1 sample in every 10,000 would test the limits of redbook CD. If dithered to 16 bit levels, seems unlikely you would notice enough difference to quibble over or worry about.

  4. #24
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    Quote Originally Posted by amirm View Post
    I actually wrote an article on this very topic . Here it is: http://www.madronadigital.com/Librar...amicRange.html

    Quick message is that ambient noise measurements are not correct basis for the lower floor. We need to perform a spectrum analysis and match it to our hearing.
    Hi Amir,

    thank you very much for that article of yours, I found it very elucidating. It certainly will lead anyone who reads it (everyone here should) to rethink the subject of noise floor. Yet I have a few issues with the observations.

    Quoting Fielder, you cite measurements of 130 dB for live music peaks. Yet Fielder leaves out the frequency distributions that are at these peaks. If he analyzes frequencies for noise floor, he needs to do the same for peaks, in order to be scientifically rigorous and coherent in his argumentation. Certainly, measuring this would be much more difficult than measurements of the noise floor, but it should be done nonetheless. I am wondering, for example, which frequencies are the ones contributing the most to the maximum of 118 dB orchestral peaks. As the Galen Audio website states (I cannot verify, but it is an interesting point): "One-third of the total power of a 75-piece orchestra comes from the bass drum."

    If the bass frequencies are contributing to SPL the most at orchestral peaks (my intuition tells me no, but it really would have to be measured), then the higher noise floor at low frequencies from Fielder's analysis comes into play.

    Furthermore, when you quote 130 dB for live music peaks from Fielder's study, this is misleading since it leaves out important details.

    (Fielder's study can be found here:
    http://www.zainea.com/Dynamic%20range.htm)

    The highest peaks of 129 dB in Fielder's study were from rock/pop concerts. But this is amplification through usually bad-sounding PA systems, and thus irrelevant for purposes of discussing high-end sound reproduction. When it comes to jazz, peaks were at 127 dB. But such loud levels are reasonably possible only in small clubs and at really close distance, and the audience present in such a small venue will ensure that even a noise floor of 40 dB is virtually impossible. More realistically, the noise floor will be around 50-60 dB minimum. This would leave a dynamic range of maximum 80 dB. And when it comes to home reproduction of such music, who in their right mind would be so crazy to shower themselves with such insane, and ear-damaging, SPL in the absence of a live audience atmosphere? Classical percussion at 122 dB as measured by Fielder is probably bass rich, which would again play into a high SPL background of low frequencies.

    For the dynamic range of CD this probably leaves as the only realistic problem orchestral music, with peaks at maximum 118 dB. Yet that was the highest measured value, and in others studies cited in Fielder's paper the values were lower. Again, these must be complete exceptions, usually it does not get that loud. I once measured a live concert of a pretty loud piece (Bartok, Concerto for Orchestra) and I was 'disappointed' that my SPL meter peaked at 92 dB. I sat in the fourth row from the stage, thus pretty close -- granted, perhaps too close since a lot of the sound may literally have washed over my head and further back it might have been somewhat louder, but nonetheless. On other occasions in other venues it did become subjectively louder, but I am sure it cannot have been that much louder (I cannot imagine more than 110 dB, which would be really a heck of a lot louder!).

    Yet even if we take 118 dB as the most extreme peaks, there is still the issue of noise floor:

    Quote Originally Posted by LL21 View Post
    It seemed by the Ken Rockwell quote above, the de facto range of CD is about 100db...? Plus, the key is what is the recording venue noisefloor...with an orchestra of 80 people, I doubt its 20db.
    LL21 makes an excellent observation here, and the noise floor caused by the presence of the musicians even in an otherwise empty concert hall will not be restricted to just low frequencies. So the real dynamic range required for this can barely be more than 90-95 dB either.

    Furthermore, who would want to listen at home at levels more than 100 dB anyway? As a routine listening level this would be ear-damaging and thus definitely not recommended. As I mentioned in my opening post, I never listen above 95-97 dB, and even at that level only in rare cases, and for short periods (I follow NIOSH recommendations). After 2 minutes of the final brass chorale of Bruckner's Fifth Symphony at that level, reproduced without appreciable distortion, I already feel pressure in my ears. And in case I listen to it, it is then always the piece that I end my listening session of the day with, since I do not want to unduly stress my ears further.

    As Tim puts it well:

    Quote Originally Posted by Phelonious Ponk View Post
    Well the range of a CD is from lower than I can hear above the noise in the quietest room in my house, to louder than I'd ever care to listen so, of course it is sufficient.

    Tim
    So yes, while I might somewhat agree that the dynamic range of CD is "on the edge" for exceptional cases, in 99.8 % or more of all real-world cases it is sufficient -- and safely so.

    Yet you seem to imply that the dynamic range of CD is insufficient on a routine basis when you say:
    "So it turns out we need high resolution audio (i.e. > 16 bits) after all if we want to make sure our distribution channel, i.e. recorded digital samples, does not add more noise than the rest of the chain. No cassette decks may apply."

    In this case, I would disagree.

    Al
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  5. #25
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    Quote Originally Posted by esldude View Post
    Just some empirical data from a 24 bit digital recording. Done with a small number of microphones, and minimal processing. 88 khz/24 bit.

    [...]

    Only about 1 sample in every 10,000 would test the limits of redbook CD. If dithered to 16 bit levels, seems unlikely you would notice enough difference to quibble over or worry about.
    Thanks, very interesting.
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  6. #26
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    Quote Originally Posted by esldude View Post
    Just some empirical data from a 24 bit digital recording. Done with a small number of microphones....
    Same recording, in a quieter portion with music, in this case solo cello I grabbed 350,000 samples. L 35 samples and R 30 samples below -120 db. L 580 samples and R 473 samples below -96 db. Or about 1.5 samples below -96 db every 1000 samples. None of these samples were contiguous. Would you hear that differently if all samples below -96db were dithered and brought up to -96 db ? I don't know, but I find it doubtful. I also would think the difference even if audible is going to be really, really small.

    I also grabbed an area with several instruments playing, but among the quietest areas with that. Out of 100,000 samples 2 in each channel were right at -120 db. and L 20 samples R 26 samples were below -96 db.

    In one of the more energetic regions I grabbed 200,000 samples. None were as low as -120 db. L 26 samples and R 15 samples were below -96 db. Peak levels were L -5.6 db and R -6.2db. And this a recording of acoustic instruments in a quiet hall, not a rock recording by any means. Only about 1 sample in every 10,000 would test the limits of redbook CD. If dithered to 16 bit levels, seems unlikely you would notice enough difference to quibble over or worry about.
    Agree with Al M. Very very interesting and helpful. Thank you!
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  7. #27
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    Quote Originally Posted by Ken Newton View Post
    Any exploration of this question should include the reading the below linked study on the topic, authored by Bob Stuart of Meridian. It was published some number of years ago, I don't recall exactly how many.

    https://www.meridian-audio.com/ara/coding2.pdf
    Thanks for that. Figures 7 and 10 assume 120 dB and a super-quiet noise floor. For this, see my post above.
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  8. #28
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    Quote Originally Posted by dallasjustice View Post
    In theory, digitally recorded red book is hi resolution.
    I am glad you would agree to that. Alas, not all in the high-end community do.
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  9. #29
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    Quote Originally Posted by LL21 View Post
    It seemed by the Ken Rockwell quote above, the de facto range of CD is about 100db...? Plus, the key is what is the recording venue noisefloor...with an orchestra of 80 people, I doubt its 20db.
    Recording venue noise-floor is been handled by the microphone(s) placement and type.
    The way the recording eng does it will capture the sound coming from the instrument and a different microphone captures the venue's 'hall sound'. This will give you very low noise floor.
    At least this is what explained to me when I did a tour in a recording studio long time ago.
    System photos here.

  10. #30
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    Sufficient for what?

    I like this forum but this thread is so subjective, that there is no right answer and often ignite spurious comments that, in the end, are so empirical, theoretical,and meaningless. Which has often lead to insulting, personal attacks, questioning members personal biases with the end result being the thread being closed.

    IMHO, a waste of bandwidth and intellectual, speculative babbling.

    Of course, the answer (sufficient dynamic range) is in the myriad of details. Pretty simple.

    GG

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