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Thread: 16 vs 24 bit converters and HA Audio quality,

  1. Default 16 vs 24 bit converters and HA Audio quality,

    I think the subject of 16 vs 24 bit HA sound, and music sound quality in general deserves a separate thread, so here goes:

    This subject will be of interest mostly to those who's hearing is good enough that it can be corrected to "reasonably" normal with respect to listening to music. At present, I fortunately fall in that category. With good headphones and a wide range equalizer, recorded music sounds quite good.

    I'm fairly new to HA's, and music through my HA's don't sound very good when compared to the equalized headphones. The HA's work well for voice, but I'm still in the initial stages of getting them set up properly to work well with music. Not there yet, but I'm still hopeful!


    A link was recently posted claiming no advantage in changing from 16 bit conversion to higher, typically 24 bit.

    See: http://www.head-fi.org/t/415361/24bi...-myth-exploded

    The author passionately defends 16 bit sound, perhaps too much so in my opinion. Although knowledgeable, he may be missing a significant point concerning the dynamic range of music. I have seen "experts" defend both viewpoints, 16 bit and 24 bit.

    A good example in favor of 24 bit conversion is found here:

    http://www.homestudiocorner.com/24-bit-vs-16-bit/

    and here:

    http://www.hearingreview.com/2013/03...ations-part-1/

    The differences of opinion seem to center around the maximum intensity of recorded music. In each case, the above authors state a value for the dynamic range, but give no reference as to where they got this value. Without listing the source and details, it is impossible to determine who is correct. There are also very likely additional factors involved, when it gets to actually putting into practice the basic principles being discussed.

    A second problem is that none of these individuals seems to be directly involved with the actual detailed design of the conversion circuitry. I personally would tend to doubt anyone who does not have such experience. Working "in the field" doesn't count in my book. Such subjects are much too complex to be debated with "true conviction" by people who are not actually doing the work!

    It will be interesting to see how this plays out!
    Last edited by bob h; 02-22-2017 at 03:34 PM.
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    You seem to have posted the same link twice, maybe by error?

    I think the 144dB for 24-bit and 96dB for 16-bit dynamic range is well established. You just gotta google more if you want to understand the technical details on this. Both the sources you cited above used the same value, right? So there's no conflicting information there.

    And I also think both sources are also in agreement that 24-bit gives more headroom (against the noise floor), so it's better to record using 24-bits vs 16-bits because you don't need to record super hot to minimize the noise floor if you use 24-bit. They're both in agreement there, too.

    The head-fi.org paper simply states that if you playback something recorded in 16 bit, and the same thing recorded in 24 bit, you most likely won't be able to tell the quality difference between them. If you have an exceptionally high noise floor, you may hear a little more noise on the playback of a 16 bit recording vs a 24-bit recording, that is if the recording material has enough of very quiet passages to enable you to detect this. But the overall quality between the 2 recordings (except for the noise floor) is not really discernable by the human ear.

    The homestudiocorner paper doesn't disagree with the head-fi.org statement either. It simply didn't address the issue of whether one can tell the difference between the quality of the 24-bit vs 16-bit recording or not, on the playback end. It simply said that it's better to record in 24-bit, but make your final master (the playback) 16-bit if you want. By this, it reaffirms what the head-fi.org paper said, that the 24-bit has the advantage for the recoding/mixing process. But on the playback, most people wouldn't be able to tell the quality between the 2 bit-dept recordings.

    So I don't see any inconsistency or disagreement between the 2 papers.
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    Doc Jake, Sorry to wake you, go back to sleep!

    Sorry, I copied the same link twice. Correct second one is:

    http://www.hearingreview.com/2013/03...ations-part-1/

    Actually I think they do disagree, most obviously on some of the basic assumptions. The "scientific principals" they do agree on, however they don't agree on the assumptions that go with these principals to answer the real world question of how to get the best sound.

    The 16 bit guy claims 60dB is enough. For one of the authors I could not spot the actual claimed level, and the other listed it as "peak values have been reported as high as 117 and 120 dB SPL.12,13 ", with references. There may also be an apples to oranges difference here, clouding the issue further.

    A third reference ( http://www.audiologyonline.com/artic...istening-12915)
    claims music to require higher levels: "even quiet music can reach levels of 105 dBA, with peaks in excess of 120 dBA". Although references are cited, they are not specifically referenced, so I have no idea where these numbers came from. (I'm not ambitious enough to search!)

    Overall, my point is that "experts" disagree on whether higher bit depths than 16 are necessary and/or useful, and we shall see how it plays out!
    Last edited by bob h; 02-22-2017 at 04:32 PM.
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  5. #5
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    Isn't all that a bit moot when your single driver receiver can only reproduce an effective bandwidth of about 10KHz with an effective dynamic range of about 90dB in the middle and around 60dB at the ends. The whole signal is going to be demodulated to its physical performance.
    Same applies at the input. Your realistic noise floor is around 20dB due to Brownian motion. Sounds greater than 110-115 dB don't require sampling as you hear them directly whether they saturate the hearing aid response or not. 96dB ought to be adequate.
    That's before you consider the personal needs of the wearer and the compression the aid uses to deal with their reduced dynamic range.
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    "Overall, my point is that "experts" disagree on whether higher bit depths than 16 are necessary and/or useful, and we shall see how it plays out!"

    When the output goes to a 1/8" diameter speaker, that all seems academic (if you expect hi fidelity music). I think I agree with the doc.
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    Yeah, been a slow day!

    I am actually surprised they can do as well as they do with small speakers, still, there's no physical reason I know of that prevents good sound out of small ones.
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    I like this third paper/link (written by Widex people) that you shared a lot. That's because it addresses the dynamic range issue specific to the HAs. But it's interesting to note that they talk about shifting the operating range of their 16-bit A/D converter and not really using the obvious solution of just going to a 24-bit A/D converter. But that's probably due to their platform/design limitations and they're stuck with finding workarounds for the 16-bit design. Other HAs like the Oticon OPN has 24-bit processing and is able to get 114 dB SPL on the input side without having to do any kind of workaround like operating range shifting.

    But again, I still don't see any conflict between all 3 papers. This Widex paper focuses the dynamic range advantage to avoid distortion at the INPUT stage of the HAs due to very loud sounds, like at a live music environment. That's just another angle and another advantage of having 24-bit A/D converter and processing. But that's a different issue entirely than saying that 16-bit processing is not good enough for music compared to 24-bit and human can tell the difference.

    What I'm trying to say is that the headroom issues that a 24-bit system solves (more noise, distortion at high input level, speech in noise due to distortion, etc), while real, does not make 16-bit processed sound have a discernible lower sound quality than 24-bit processed sound that a normal person can tell. For most normal hearing situations, they'll sound the same, quality wise. If you play music from your sound system or watch TV at a reasonable listening level, I don't think you can tell the difference between 16-bit and 24-bit HAs.

    Now if you go to a concert or listen to live music, then 24-bit HAs will sound better for sure because they can take in the higher dynamic range at the input to handle louder volumes and attacks of the live instruments and don't get distorted or suffer from input dynamic compression. But even the Widex 16-bit system they talk about in the 3rd paper can manage loud inputs after they shift its operating range. So if you wear that 16-bit Widex HA at a live music concert, you can probably enjoy the live music pretty well, too, even though it's only 16 bits. It just goes to show that headroom/dynamic range and sound quality, while inter-related, are different attributes and shouldn't be combined and generalized together in a definitive way.
    Last edited by Volusiano; 02-22-2017 at 05:55 PM.
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    Actually, I pretty much agree. 16 bit should be adequate, and I also have my suspicions that 24 bit may be as much of a marketing point as an engineering essential. There are likely other areas that are more important to good quality sound out of HA's.

    I am puzzled though by the number of posters who are convinced that their digital HA's aren't very good at music. Is there some specific weak link, or have they just not spent enough time on this? From the technology, it seems like that should be easy with digital.

    My own experience so far has been great for speech, less than satisfactory for music, but as I said below, I'm still hopefull! (they're 16 bit devices, but I doubt that's significant!)
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  10. #10
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    I don't have a good enough understanding to explain it adequately, but I think it has to do with compression. Soft sounds are amplified much more than loud sounds and the amplification varies depending on the frequency. It's beneficial for understanding speech, but not for enjoying music. Better is likely a good set of headphones. There are others who can do a much better job of explaining.

    Quote Originally Posted by bob h View Post
    Actually, I pretty much agree. 16 bit should be adequate, and I also have my suspicions that 24 bit may be as much of a marketing point as an engineering essential. There are likely other areas that are more important to good quality sound out of HA's.

    I am puzzled though by the number of posters who are convinced that their digital HA's aren't very good at music. Is there some specific weak link, or have they just not spent enough time on this? From the technology, it seems like that should be easy with digital.

    My own experience so far has been great for speech, less than satisfactory for music, but as I said below, I'm still hopefull! (they're 16 bit devices, but I doubt that's significant!)
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