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Thread: Audible Jitter/amirm vs Ethan Winer

  1. #121
    [WBF Founding Member] Moderator RBFC's Avatar
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    Ron,

    All tones generate subharmonics as well, which in the case of 40kHz, would be back in the audible range.

    Lee
    Lee Aldridge

    I post my own opinions except when posting as a moderator in green.

  2. #122
    [WBF Founding Member] Ron Party's Avatar
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    Oops, I know. I had intended to quote more of Marty's post than just that one sentence, so I'll try to do it this time:

    Quote Originally Posted by marty View Post
    Ethan's key argument that jitter, if it is 100dB below the signal, must by definition be inaudible, reminds me of the old argument that an amplifier's performance at 40KHz must be irrelevant since we can only hear up to ~20KHz. We now know that not to be the case as the harmonics of signals at 40KHz may be heard in the audible range. The main reason I think jitter is likely audible is the recent work of some vehement anti-jitterholics such as Ed Meitner, whose recent effort , the XDS1, greatly impressed me.
    Now I will reask Marty this question: how do we know that? How do we connect those 2 sentences? Where is the proof of audibility?
    Peace.

    Ron Party

  3. #123
    Member Sponsor [Technical Expert] DonH50's Avatar
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    A question: Are the subharmonics generated in the ear? It takes a nonlinearity to generate subharmonic (mixing) products, and I am curious if the ear (or ear/brain system) does this. I do not know.

    Curious - Don
    Don Herman
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  4. #124
    WBF Technical Expert (Speakers & Audio Equipment)/Member Sponsor [Technical Expert] garylkoh's Avatar
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    Quote Originally Posted by DonH50 View Post
    A question: Are the subharmonics generated in the ear? It takes a nonlinearity to generate subharmonic (mixing) products, and I am curious if the ear (or ear/brain system) does this. I do not know.

    Curious - Don
    I'm sure that you will like this one:
    http://lab.rockefeller.edu/hudspeth/...pf_bifurcation

    The ear is a non-linear system with the inner hair cells operating near dynamic instability. The threshold of hearing (4dB at 1kHz is commonly accepted in scientific circles) corresponds to air vibrations on the order of a tenth of an atomic diameter. This means that without the non-linear system of the ear, just the Brownian movement of the air molecules adjacent to the ear-drum would drive all of us batty.

    The ear also produces sound in a non-linear function to form distinguishing interference to help improve sensitivity to micro-dynamic information way above the threshold of hearing.
    http://emedicine.medscape.com/article/835943-overview

    So to answer your question, yes and yes.
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  5. #125
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    There is also a bit more information here: http://en.wikipedia.org/wiki/Ultrasonic_hearing

  6. #126
    WBF Technical Expert (Speakers & Audio Equipment)/Member Sponsor [Technical Expert] garylkoh's Avatar
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    Thanks. There's also information on the lower frequencies: http://en.wikipedia.org/wiki/Infrasound

    Frequencies below 20Hz result in feelings of awe - which may be why full range loudspeakers are more impressive??
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  7. #127
    [WBF Founding Member] Ron Party's Avatar
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    Quote Originally Posted by amirm View Post
    There is also a bit more information here: http://en.wikipedia.org/wiki/Ultrasonic_hearing
    We've had a tiny bit of discussion about the claims made by Oohashi et al., and there has been a ton of discussion about those claims at AVS and hydrogenaudio. Suffice to say, the purported results of their testing and thus their claim of audibility have never been successfully repeated. To the contrary, there are more credible explanations of their results. If JJ was participating in this thread, he'd tear Oohashi and the true believers a new one.
    Peace.

    Ron Party

  8. #128
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    I did not put that link up there as proof of anything but rather, answering Don's question about some sources on the topic. Wiki articles that are short are always a red signal to me and that one was no objection. If JJ has something to say about the topic, he would do well to go and edit that article.

    Personally, I like to go 20% or so above 20Khz for two reasons:

    1. There is some evidence of people hearing above 20 Khz and the modulation effects thereof. See below.

    2. It gets rid of a lot of arguments that way .

    Going beyond 24-25Khz doesn't get my vote as I worry who can verify what the equipment is doing in that region.

    The best read along these lines is from Bob Stewart of Meridian fame. His writing is rather pragmatic and nice middle of the road like mine. http://www.meridian-audio.com/w_paper/Coding2.PDF

    "PSYCHOACOUSTIC DATA ON HIGH-FREQUENCY HEARING

    There is very little hard evidence to suggest that it is important to reproduce sounds above 25kHz.
    Instead there tends to be a general impression that a wider bandwidth can give rise to fewer in-band
    problems. However, there are a few points to raise before dismissing audible content above 20kHz as
    unimportant.

    The frequency response of the outer and middle ear has a fast cut-off rate due to combined roll-off in the
    acoustics of the meata and in mechanical transmission. There also appears to be an auditory filter cutoff
    in the cochlea itself.

    The cochlea operates ‘top-down’, so the first auditory filter is the highest in frequency. This filter
    centres on approximately 15kHz, and extrapolation from known data suggests that it should have a
    noise bandwidth of approximately 3kHz. Middle-ear transmission loss seems to prevent the cochlea
    from being excited efficiently above 20kHz.

    Bone-conduction tests using ultrasonics have shown that supersonic excitation ends up in this first ‘bin’.
    Any supersonic information arriving at above 15kHz therefore ends up here, and its energy will
    accumulate towards detection. It is possible that in some ears a stimulus of moderate intensity but of
    wide bandwidth may modify perception or detection in this band, so that the effective noise bandwidth
    could be wider than 3kHz.

    The late Michael Gerzon surmised that any in-air content above 20–25kHz derived its significance from
    non-linearity in the hearing transmission, and that combinations of otherwise inaudible components
    could be detected through any resulting in-band intermodulation products.

    There is a powerful caution against this. As far as the author knows, music spectra that have measured
    content above 20kHz always exhibit that content at such a low spl that it is unlikely that the (presumed)
    lower spl difference distortion products would be detectable and not masked by the main content."

  9. #129
    [WBF Founding Member] Ron Party's Avatar
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    Thumbs up

    Quote Originally Posted by amirm View Post
    Personally, I like to go 20% or so above 20Khz for two reasons:

    1. There is some evidence of people hearing above 20 Khz and the modulation effects thereof. See below.

    2. It gets rid of a lot of arguments that way ."[/i]
    I'm 100 [ or should I say 120? ;-) ] percent in agreement with you on number 1. Actually, I like your number 2 as well.
    Peace.

    Ron Party

  10. #130
    WBF Technical Expert (Speakers & Audio Equipment)/Member Sponsor [Technical Expert] garylkoh's Avatar
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    There's still no definitive answer to whether frequencies about 20kHz are needed. However, this study shows that with a crash cymbal, 40% of the total sound energy is above 20kHz.
    http://www.its.caltech.edu/~boyk/spectra/spectra.htm

    I've tried some experiments with recording jangling keys (68% of energy above 20kHz), sampling at 96kHz and I can always tell if I put in a filter at 30kHz. However, that may be because of my badly implemented filter, or my lousy recording technique.
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