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

  1. #11

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    Quote Originally Posted by MDB View Post
    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.
    I think you hit the nail on the head there, MDB. As mentioned in the Widex paper (the 3rd link that Bob shared), dynamic compression of the input of 16-bit system is an easy/cheap way to prevent clipping/distortion when subjected to loud sound. It's kinda like somebody holding the input volume knob and if the sound gets too loud, he turns the volume knob down to avoid distortion, and when the sound gets softer, he turns the input volume knob back up. If you hear very expressive music that changes volume very frequently and quickly, the effect of cranking the volume knob down and up and down and up will start making the music sound funny and not natural anymore. That's what they call the pumping effect. And dynamic compression may very well be set differently at different frequencies as well, making it sound even more weird.

    For speech it's not as bad because speech tends to be more monotonous and doesn't fluctuate as much in volume. But if you add speech with loud noise then it starts to get worse because the dynamic compression to cut down on the noise level negatively suppress the volume of the speech as well.
    HA wearer since the 1990's > Rexton Insite+ CIC (2011-2016) > Oticon OPN RITE (2016)

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  2. #12

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    Absolutely. Analog aids merely amplified, thus, no weird artifacts from compression and fancy software algorithm manipulations. Of course, analog aids just plain clipped and distorted when you hit their limits, but until that point, they did music better than digital.

    Quote Originally Posted by Volusiano View Post
    I think you hit the nail on the head there, MDB. As mentioned in the Widex paper (the 3rd link that Bob shared), dynamic compression of the input of 16-bit system is an easy/cheap way to prevent clipping/distortion when subjected to loud sound. It's kinda like somebody holding the input volume knob and if the sound gets too loud, he turns the volume knob down to avoid distortion, and when the sound gets softer, he turns the input volume knob back up. If you hear very expressive music that changes volume very frequently and quickly, the effect of cranking the volume knob down and up and down and up will start making the music sound funny and not natural anymore. That's what they call the pumping effect. And dynamic compression may very well be set differently at different frequencies as well, making it sound even more weird.

    For speech it's not as bad because speech tends to be more monotonous and doesn't fluctuate as much in volume. But if you add speech with loud noise then it starts to get worse because the dynamic compression to cut down on the noise level negatively suppress the volume of the speech as well.
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  3. Default

    Is there some technical reason for the poor reputation digitals seem to have for music? It seems like it should be simple to make them at least as good. Or is it just lack of acceptance. Some people swear by their old analog stereo, even though double blind tests don't seem to support their claims!
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  4. #14

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    Not necessarily technical but H/A are geared toward speech and not music as that is what the developers think that we need.

  5. #15

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    My new Widex Unique music mode is pretty good. It shuts off most (not all) processing and turns off compression filters. It can be done, it's just hasn't been done very well to date.

    Quote Originally Posted by bob h View Post
    Is there some technical reason for the poor reputation digitals seem to have for music? It seems like it should be simple to make them at least as good. Or is it just lack of acceptance. Some people swear by their old analog stereo, even though double blind tests don't seem to support their claims!
    ..250..500..1000..2000..4000..8000
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    R: no hearing

  6. #16

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    I think usually good music reproduction is synonymous with being able to reproduce good bass, which is a critical (but not only) attribute for a lot of contemporary music genres. The HA receiver just doesn't have the physical construction to enable this. There's only 1 tiny little receiver that has to be optimized for the whole frequency range, which is no match for a speaker system with bass and mid range speakers and tweeter speakers all separate.

    The other aspect is what we've discussed earlier in the thread, the lack of sufficient dynamic range on the input mic, as well as the A/D converter, to handle the loudness of musical instruments live. Digital tricks used to avoid distortions like dynamic compression also cause pumping which makes music more unnatural at times.

    Then there's also limitation on the HA mics themselves. Due to their tiny construction, I'm sure they're no match compared to professional mics that are 100 times bigger in size and with much better pick up materials.

    One of the things that is essential in HAs is feedback control. One of the way to minimize feedback is to run the feedback test throughout all the frequency channels and reduce the gain of the resonant frequencies that cause feedback. First off, the obvious trade-off here is the reduction in headroom of the frequency bands where gain reduction is necessary for feedback control. Secondly, the effect is worse for HAs with less number of frequency bands (like 8 or 16) because the gain reduction may be more widespread than it needs to be. HAs with more frequency bands like 24 of 48 channels suffer less of the headroom reduction effect because of the ability to fine tune the gain reduction to a much smaller frequency bandwidth the higher the number of channels there is.

    Thirdly, like JustEd was saying, if the HA is running a program geared toward speech, then things done to promote speech like noise reduction and directional beam forming, sometimes increasing the gain on the frequency bands where speech resides, or reducing reverb or echos in an open room, can ruin the quality of the music. That's why most HAs have a music program which essentially removes all of the processing geared toward speech so that you can hear the music sound unadultrated. But some of the modern HAs now may have auto listening environment detection and auto program transition, which may not necessarily be smart enough to know what is music and what is just a lot of noise, so there may be a good chance for the wrong (non-music) program to be selected when music is being played.

    Listening to music in a noisy environment (like while driving a car) is another challenge. How would the HA be smart enough to know what is music and what is noise. If you switch to a music program then you'll have to deal with the noise because most likely music programs don't have noise reduction. If you switch to a car noise program then the noise reduction designed for it will stifle the music.

    But direct streaming is one area where you can eliminate a lot of the variables that are limitations, like mic construction/sensitivity/dynamic range, digital processing geared toward speech, management of noise, etc. That's why direct streaming should sound pretty darn good if you have the good source content and quality, and the right expectation about the limitation of the tiny little receiver that's tasked to reproduce the sound in your ear.
    Last edited by Volusiano; 02-23-2017 at 03:08 PM.
    HA wearer since the 1990's > Rexton Insite+ CIC (2011-2016) > Oticon OPN RITE (2016)

    KHz 0.25...0.5...0.75...1.0...1.5...2.0...3.0...4.0... 6.0...8.0

    Left ...10...10....10.....30.....70....75....80....95.. ..90....80
    Right .25...30....40.....55.....75....85....90....90...1 00...100

  7. #17
    Join Date
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    Somewhere on the forum somebody gave an excellent explanation. The problem is dynamic range. With normal hearing, one has the equivalent of a blimp's worth of dynamic range (from very quiet sounds to very loud--perhaps 100-120dB of range) For hearing impaired, it's crammed into a bicycle inner tube--the dynamic range might only be 40dB or less(80-120db)

    Quote Originally Posted by bob h View Post
    Is there some technical reason for the poor reputation digitals seem to have for music? It seems like it should be simple to make them at least as good. Or is it just lack of acceptance. Some people swear by their old analog stereo, even though double blind tests don't seem to support their claims!
    .25 .5 1 1.5 2 3.0 4.0 6.0 8.0

    15 15 20 30 30 55 75 90 NR ​KS7
    10 10 20 15 25 35 65 85 95 WRS 100/92@45/40

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