Hello People, With SACD and DVD-A out, I've thought a bit about the senseless overkill these standards promote. In the process, I have acknowledged that there may be a few people in the world who truly do hear over 20 kHz (1 in 1000? Anyone got any stats on this?). So the 44.1 kHz of CD may not quite get it if you account for things like the antialiasing filter rolloff. So if we were to up the sample rate, where should we put it? And what about resolution? Should it change as well? Here's what I've come up with (at least on the back of a napkin): 64 kHz sample rate, 32-bit data. This should allow for more than ample overhead in spectrum width and resolution without going completely crazy (as in, e.g., 192 kHz). It just seems to have a really nice symmetry about it and utility to it. The SHARC already has 32-bit fixed-point processing capability, and I can see future DSPs geared toward audio having that same width. If you can hear about 30 kHz, you're not human. So this oughta cover it, right??? Just pipe dreaming, but was wondering what the group thinks. Comments? -- % Randy Yates % "...the answer lies within your soul %% Fuquay-Varina, NC % 'cause no one knows which side %%% 919-577-9882 % the coin will fall." %%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO http://home.earthlink.net/~yatescr
New Digital Audio Standard?
Started by ●December 22, 2003
Reply by ●December 22, 20032003-12-22
Hi Randy, Isn't the reason that the sampling frequency has increased, that auditorial perception goes beyond 20kHz? For pure tone signals 20 Khz is the limit, but for transients and/or harmonic components the human is sensitive for higher frequencies? Cheers Thomas S "Randy Yates" <yates@ieee.org> wrote in message news:36DFb.9119$wL6.871@newsread1.news.atl.earthlink.net...> Hello People, > > With SACD and DVD-A out, I've thought a bit about the senseless overkill > these standards promote. In the process, I have acknowledged that there > may be a few people in the world who truly do hear over 20 kHz (1 in 1000? > Anyone got any stats on this?). So the 44.1 kHz of CD may not quite get it > if you account for things like the antialiasing filter rolloff. > > So if we were to up the sample rate, where should we put it? And whatabout> resolution? Should it change as well? > > Here's what I've come up with (at least on the back of a napkin): 64 kHz > sample rate, 32-bit data. This should allow for more than ample overhead > in spectrum width and resolution without going completely crazy (as in, > e.g., 192 kHz). It just seems to have a really nice symmetry about it and > utility to it. The SHARC already has 32-bit fixed-point processingcapability,> and I can see future DSPs geared toward audio having that same width. If > you can hear about 30 kHz, you're not human. So this oughta cover it,right???> > Just pipe dreaming, but was wondering what the group thinks. Comments? > -- > % Randy Yates % "...the answer lies within your soul > %% Fuquay-Varina, NC % 'cause no one knows which side > %%% 919-577-9882 % the coin will fall." > %%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO > http://home.earthlink.net/~yatescr
Reply by ●December 22, 20032003-12-22
Heureka wrote:> Hi Randy, > > Isn't the reason that the sampling frequency has increased, that auditorial > perception goes beyond 20kHz? For pure tone signals 20 Khz is the limit, but > for transients and/or harmonic components the human is sensitive for higher > frequencies?Hi Heureka, I don't remember ever hearing that. In fact, I've heard the opposite, but in general. That is, generally, a tone is easier to detect than anything else. I don't see why it would make a difference whether it's above or below 20 kHz. Do you have a reference? --Randy> > Cheers > Thomas S > > > "Randy Yates" <yates@ieee.org> wrote in message > news:36DFb.9119$wL6.871@newsread1.news.atl.earthlink.net... > >>Hello People, >> >>With SACD and DVD-A out, I've thought a bit about the senseless overkill >>these standards promote. In the process, I have acknowledged that there >>may be a few people in the world who truly do hear over 20 kHz (1 in 1000? >>Anyone got any stats on this?). So the 44.1 kHz of CD may not quite get it >>if you account for things like the antialiasing filter rolloff. >> >>So if we were to up the sample rate, where should we put it? And what > > about > >>resolution? Should it change as well? >> >>Here's what I've come up with (at least on the back of a napkin): 64 kHz >>sample rate, 32-bit data. This should allow for more than ample overhead >>in spectrum width and resolution without going completely crazy (as in, >>e.g., 192 kHz). It just seems to have a really nice symmetry about it and >>utility to it. The SHARC already has 32-bit fixed-point processing > > capability, > >>and I can see future DSPs geared toward audio having that same width. If >>you can hear about 30 kHz, you're not human. So this oughta cover it, > > right??? > >>Just pipe dreaming, but was wondering what the group thinks. Comments? >>-- >>% Randy Yates % "...the answer lies within your soul >>%% Fuquay-Varina, NC % 'cause no one knows which side >>%%% 919-577-9882 % the coin will fall." >>%%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO >>http://home.earthlink.net/~yatescr > > >-- % Randy Yates % "...the answer lies within your soul %% Fuquay-Varina, NC % 'cause no one knows which side %%% 919-577-9882 % the coin will fall." %%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO http://home.earthlink.net/~yatescr
Reply by ●December 22, 20032003-12-22
Randy Yates wrote:> With SACD and DVD-A out, I've thought a bit about the senseless > overkill these standards promote. In the process, I have acknowledged > that there may be a few people in the world who truly do hear over 20 > kHz (1 in 1000? Anyone got any stats on this?). So the 44.1 kHz of CD > may not quite get it if you account for things like the antialiasing > filter rolloff.As well as the obvious reasons ("people will spend the money", "my dog likes to listen too", and anything beginning with "it's more complicated than that")... Isn't part of the reason to compensate for incompetent engineers doing a bad job within the limitations imposed on them by the format? Children playing too close to the road, if you will. Moving things out an extra few kHz isn't going to save them; you have to give them so much space they can't possibly hurt themselves (or the consumer).
Reply by ●December 22, 20032003-12-22
Heureka wrote:> Isn't the reason that the sampling frequency has increased, that auditorial > perception goes beyond 20kHz? For pure tone signals 20 Khz is the limit, but > for transients and/or harmonic components the human is sensitive for higher > frequencies?Randy Yates wrote:> I don't remember ever hearing that. In fact, I've heard the opposite, but > in general. That is, generally, a tone is easier to detect than anything > else. I don't see why it would make a difference whether it's above or > below 20 kHz.If you'll excuse me for talking all airy-fairy, pseudo-scientific, metaphysical, and without references for just a moment... It is a possibility that even if your brain doesn't say "there is a tone at 21kHz, 30 degrees to your right", it may still consider that information in relation to other frequencies as part of its complex analysis and modelling of the world around you. That tone on its own is more likely an internal hardware fault than anything created in the natural world, something which your brain will automatically discard or rationalise. So, you may not be able to consciously say that there is or is not a tone at some frequency above 20kHz, but that tone could still affect your perception of other sound below 20kHz. Proving or disproving the effect would be very difficult, because you're not simply looking for yes/no answers but changes in perception... perhaps only slight changes in perception in practiced listeners.
Reply by ●December 23, 20032003-12-23
In article FXNFb.5578$IM3.144@newsread3.news.atl.earthlink.net, Randy Yates at yates@ieee.org wrote on 12/22/2003 21:41:> Heureka wrote: > >> Isn't the reason that the sampling frequency has increased, that auditorial >> perception goes beyond 20kHz? For pure tone signals 20 Khz is the limit, but >> for transients and/or harmonic components the human is sensitive for higher >> frequencies? > > I don't remember ever hearing that. In fact, I've heard the opposite, but > in general. That is, generally, a tone is easier to detect than anything > else. I don't see why it would make a difference whether it's above or > below 20 kHz. > > Do you have a reference?i don't really have a reference (maybe http://www.mytekdigital.com/DSDvsPCMdebate.txt ), but years ago we were debating on some mailing list or another the merits of DSD (what became SACD) vs. PCM . one experiment that some of us were gonna try (and i think that Bob Katz did) was whether or not we could really hear above 20 kHz. i thought that the meaning of the question is synonymous with whether or not we could really hear the difference between some audio that is filtered with a virtual brick wall filter (at 20 kHz) and the same audio not filtered. we thought that the experiment needed some audio that is sampled at a very high sampling rate (96 or 192 kHz), has significant content above 20 kHz (so there is something to filter out), some well designed (flat, flat, flat below 20 kHz) linear phase FIR LPFs, and a good testing protocol (blind or double blind, AB or ABX). while discussing it, there was a lot of talk about that pre-echo issue (from pass-band ripples) and other transient stuff (that people thought might leave artifacts, but i dunno how you can talk about removing this stuff above 20K and not leave transients, that's what it's about!) so we decided on phase-linear FIR filters that were designed with MATLAB's firls() (instead of remez()), had damn flat passband (0.002 dB) up to somewhere around 20 kHz and the transition band between 20 and 22 kHz (so above 22.05 kHz it would be virtually totally wiped out spectrum and eligible for resampling at 44.1). i still got the lpf.m file (appended below). i think they got a good recording of castanets or something. and, because of the dithered quantization that happened in the FIR LPF, they added the same dither to and requantized the control (unfiltered) sound so we could compare apples to apples as much as possible. anyway, Bob Katz (digido.com, who was a bit predisposed that he *would* hear a difference) was gonna administer the test in his studio to other subjects and, to his surprise, *he* could not hear it. so he didn't even do the test! i don't know where he is now about DSD, SACD, etc. but i thought that was interesting. of course, what would be more interesting is if someone (say a school or similar institution) with a very modern Pro Tools setup would do that double-blind AB test with both golden eared and clay eared people (and everyone in between) as test subjects. they really should settle, at what frequency that everything above can be lost (resulting in whatever transients) and statistically no one can hear the difference. that should settle the PCM sample-rate issue once and for all (except for the Monster Cable disciples). r b-j % lpf.m % Basic Parks-McClellan (or Least Squares) Low-Pass Filter Design if exist('filename') ~= 1, filename = 'lpfcoefs.txt'; % filename for FIR coefs output end; % the input parameters are not changed if they already exist if exist('SR') ~= 1, SR = 192; % sampling rate end; if exist('PB') ~= 1, PB = 20; % top of passband region (where filter should be flat and 0 dB) end; if exist('PBR') ~= 1, PBR = 0.002; % max passband ripple in dB which is twice the max error in passband end; if exist('SB') ~= 1, % SB = SR/2 - PB; SB = 22.5; % bottom of stopband region (where filter should be flat and -inf dB) end; if exist('SBG') ~= 1, SBG = -150; % max stop band gain in dB end; R = (PB + SB)/SR; % Number of required FIR taps, from a formula in Oppenhiem & Schafer p. 480 % the more accurate MATLAB function remlpord() could be used instead. % for nicety, we always round up to the nearest odd number of FIR taps. % when N is odd, the delay (N-1)/2 is always an integer number of samples N = 2*ceil(0.0342416*SR*(-0.5*SBG - 10*log10(10^(0.5*PBR/20)-1) - ... 13)/(SB-PB) - 0.5) + 1 if 0 % set this to 1 if you wanna get coefficients for % windowed sinc LPF (for testing) h = zeros(1, N+1); % zero the whole thang t = linspace(-R*(N-1)/2, R*(N-1)/2, N); h = [0 (R*sinc(t)) .* kaiser(N, 0.1102*(-SBG-8.7))'] ; % kaiser windowed sinc() clear t; else W = ( (10^(0.5*PBR/20) - 1) )/( 10^(SBG/20) ) % linear stopband/passband weighting ratio f = [0 PB/(0.5*SR) SB/(0.5*SR) 1]; % Define passband and stopband regions m = [1 1 0 0]; % Define passband and stopband magnitudes w = [1 W ]; % Define passband and stopband error weights h = zeros(1, N+1); h = [0 firls(N-1, f, m, w)]; % Compute impulse response from Least Squares % h = [0 remez(N-1, f, m, w)]; % Compute impulse response from Parks-McClellan end % h(1) = 0 and h((N+1)/2) = max % symmetry: h((N+1)/2 + k) = h((N+1)/2 - k) % this should result in zero phase % in the frequency response. H = fft([h([(N+1)/2+1:N+1]) zeros(1, 3*(N+1)) h([1:(N+1)/2])]); % fft after zero-padding to extend length by factor of 4 freq = linspace(0, 1-2/(N+1), 2*N+1); % set of frequencies from DC to just under Nyquist plot(h/R, '.'); % plot scaled impulse response pause; % dB by linear freq plot plot((SR/2)*freq, 20*log10(abs(H(1:2*N+1))+1.0e-10)); pause; % look closely at passband ripple axis([0 0.5*(SR/2) -0.01 0.01]); pause; % dB by log freq plot, skip DC semilogx((SR/2)*freq(2:2*N+1), 20*log10(abs(H(2:2*N+1))+1.0e-10), 'g'); pause; % look closely at passband ripple axis([0.05*(SR/2) 0.5*(SR/2) -0.01 0.01]); outfile = fopen(filename,'wt+'); fprintf(outfile, '%1.8e\n', h(2:N+1)); fclose(outfile);
Reply by ●December 23, 20032003-12-23
In article bjqkb1-8pj.ln1@toast.void.nil, Simon Hosie at gumboot@learcay.etnay.nzsomething.invalid wrote on 12/22/2003 22:49:> Heureka wrote: >> Isn't the reason that the sampling frequency has increased, that auditorial >> perception goes beyond 20kHz? For pure tone signals 20 Khz is the limit, but >> for transients and/or harmonic components the human is sensitive for higher >> frequencies? > > Randy Yates wrote: >> I don't remember ever hearing that. In fact, I've heard the opposite, but >> in general. That is, generally, a tone is easier to detect than anything >> else. I don't see why it would make a difference whether it's above or >> below 20 kHz. > > If you'll excuse me for talking all airy-fairy, pseudo-scientific, > metaphysical, and without references for just a moment... > > It is a possibility that even if your brain doesn't say "there is a tone > at 21kHz, 30 degrees to your right", it may still consider that > information in relation to other frequencies as part of its complex > analysis and modelling of the world around you. That tone on its own is > more likely an internal hardware fault than anything created in the > natural world, something which your brain will automatically discard or > rationalise. > > So, you may not be able to consciously say that there is or is not a > tone at some frequency above 20kHz, but that tone could still affect > your perception of other sound below 20kHz. Proving or disproving the > effect would be very difficult, because you're not simply looking for > yes/no answers but changes in perception... perhaps only slight changes > in perception in practiced listeners.Simon, that is not what we mean when we say that it is unlikely that we can really hear above 20 or 22 or 2x kHz. what we mean is that if *all* of the content above that threshold was removed (or some spurious content added, at reasonable levels), that we could not hear the difference. that is, will a brick-wall LPF make a sonic difference? r b-j
Reply by ●December 23, 20032003-12-23
Simon Hosie wrote:> Heureka wrote: > >>Isn't the reason that the sampling frequency has increased, that auditorial >>perception goes beyond 20kHz? For pure tone signals 20 Khz is the limit, but >>for transients and/or harmonic components the human is sensitive for higher >>frequencies? > > > Randy Yates wrote: > >>I don't remember ever hearing that. In fact, I've heard the opposite, but >>in general. That is, generally, a tone is easier to detect than anything >>else. I don't see why it would make a difference whether it's above or >>below 20 kHz. > > > If you'll excuse me for talking all airy-fairy, pseudo-scientific, > metaphysical, and without references for just a moment... > > It is a possibility that even if your brain doesn't say "there is a tone > at 21kHz, 30 degrees to your right", it may still consider that > information in relation to other frequencies as part of its complex > analysis and modelling of the world around you. That tone on its own is > more likely an internal hardware fault than anything created in the > natural world, something which your brain will automatically discard or > rationalise. > > So, you may not be able to consciously say that there is or is not a > tone at some frequency above 20kHz, but that tone could still affect > your perception of other sound below 20kHz. Proving or disproving the > effect would be very difficult, because you're not simply looking for > yes/no answers but changes in perception... perhaps only slight changes > in perception in practiced listeners.A test is easy. In the continuous presence of an audible tone, turn a near-ultrasonic tone on and off. See if you or others can tell when it's on. Traditional theory implies that even marginally audible high tones will be masked by the lower ones, but there have been reports to the contrary. Wishful thinking may be the root, but any claim is weak without a test. Do we want to allow the existence of a phenomenon which we agree can never be manifest? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●December 23, 20032003-12-23
"Randy Yates" <yates@ieee.org> wrote in message news:36DFb.9119$wL6.871@newsread1.news.atl.earthlink.net...> [...] > Here's what I've come up with (at least on the back of a napkin): 64 kHz > sample rate, 32-bit data. This should allow for more than ample overhead > in spectrum width and resolution without going completely crazy (as in, > e.g., 192 kHz). It just seems to have a really nice symmetry about it and > utility to it. [...]That would be with 8 channels, I presume? How about the regular 5.1 plus up and down? You could create whole new markets for speaker ceiling mounts and sunken floor enclosures. OK, maybe that's a bit much ;-) 64 kHz seems like a good rate, though. As Simon says, 44.1 is cutting it too close for comfort, and 64 isn't excessively more if good reproduction is important to you. Wouldn't you be afraid to drive over a bridge that was designed to be only a few % stronger than necessary? Me too, because I wouldn't trust the engineers to know everything significant there is to know about the requirements, just like I don't really believe that we know everything significant there is to know about hearing.
Reply by ●December 23, 20032003-12-23
Matt Timmermans wrote:> "Randy Yates" <yates@ieee.org> wrote in message > news:36DFb.9119$wL6.871@newsread1.news.atl.earthlink.net... > >>[...] >>Here's what I've come up with (at least on the back of a napkin): 64 kHz >>sample rate, 32-bit data. This should allow for more than ample overhead >>in spectrum width and resolution without going completely crazy (as in, >>e.g., 192 kHz). It just seems to have a really nice symmetry about it and >>utility to it. [...] > > > That would be with 8 channels, I presume? How about the regular 5.1 plus up > and down? You could create whole new markets for speaker ceiling mounts and > sunken floor enclosures. OK, maybe that's a bit much ;-)Yeah. Let's just stick with above-floor systems. ;) The channel count question is a whole 'nuther issue. I was just focusing on this sample rate insanity, and to a lesser extent, bit width.> 64 kHz seems like a good rate, though. As Simon says, 44.1 is cutting it > too close for comfort, and 64 isn't excessively more if good reproduction is > important to you. Wouldn't you be afraid to drive over a bridge that was > designed to be only a few % stronger than necessary? Me too, because I > wouldn't trust the engineers to know everything significant there is to know > about the requirements, just like I don't really believe that we know > everything significant there is to know about hearing.But even in bridges and such, how much is enough? 10x? 100x? -- % Randy Yates % "...the answer lies within your soul %% Fuquay-Varina, NC % 'cause no one knows which side %%% 919-577-9882 % the coin will fall." %%%% <yates@ieee.org> % 'Big Wheels', *Out of the Blue*, ELO http://home.earthlink.net/~yatescr
