Re: [music-dsp] a weird but salient, LTI-relevant question
On 5/19/14 10:01 PM, Sampo Syreeni wrote: On 2014-05-08, Risto Holopainen wrote: [...] I recall a composer collegue once complaining about repetition in the noise generator of Csound. I think they used a random generator with period 2^16 in those days, but it's been improved now. That's precisely where I landed with this thing, originally. My PRNG wasn't Csound's but Turbo Pascal's. Still, a linear conguential generator with 16 bit state. That's unusable because you can hear the repetition. But the real question is, *why* *can* you hear it? um, because it repeats? like nearly every second? What's the neural mechanism which lets you such long term structure even in fully randomized sound? What does it tell you about human hearing, and its theory, and the limits of that theory, precisely? given any short set of random numbers, if you look at a shorter subset of it, you will see that some particular frequency components will stand out more than others. you will hear those frequency components pop out at you. likely you won't notice or make a mental note of it because the next second, some other component at a different frequency will pop out. but if the sequence repeats every 65535/44100 second these temporal artifacts of the random signal will certainly be noticed. -- r b-j r...@audioimagination.com Imagination is more important than knowledge. -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
On May 11, 2014, at 7:42 PM, Sampo Syreeni de...@iki.fi wrote: On 2014-05-08, Nigel Redmon wrote: The bottom line, I think, is that yes white noise is random, but the low frequency components are, well, low frequency. You can't here 1Hz though, evenif you can hear its contray 1s repeat frequency. True. But I meant that it seemed that repeating the repetition of a low-frequency artifact is easier to hear that artifacts that change quickly. I’m just relaying an observation, not saying I understand it. That is, in listening to white noise, if you pay attention to different frequency area, you have a hiss on top, and in the low part you can hear a constantly changing and morphing series of chugs and things that I don’t know how to describe. It’s pretty easy to latch onto one of those repeating when it gets down in the 2-second range. That’s the best I can seem to describe it :-/ Now take a long enough random sequence with all of its content under 200Hz or so filtered out by DFT. Repeat the DFT block. Can you still hear the repetition? By definition, there's no bump there, either. At least if you did it right. Anyway, like I said, I’ve been through this before so there were no surprises. Sampo, were you looking for a particular revelation? I’m not sure if I’m listening for what you were getting at. You prolly are. You seem to know what I'm getting at in full. But if you think about what that means, really, it just is *really* difficult to see what *these* LTI implictions have to do with the *shorter* time LTI implications we normally work with and e.g. base our codecs on. And really, I just *love* the people of old who know about this or old, and/or try it out anew. :) Haha—yeah, that’s me, old guy ;-) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2-- -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
On 2014-05-08, Theo Verelst wrote: About the noise, I'll say it only one time: IS YOUR NOISE SOURCE BANDWIDTH LIMITED, [...] This sort of thing is precisely why I left it for you and everybody else to produce. By yourselves. So that only yourself is then to blaim. It really doesn't matter too much as long as you loop the noise well enough. No splicing artifacts which would make the noise easily discernible from looped noise of the same class. Even somewhat lowpassed noise wouldn't be *too* bad -- but then in looping you can't ever lowpass it except using a cyclic convolution, or the splice point can be heard. So, Theo, no analog processing here. -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
On 2014-05-08, robert bristow-johnson wrote: where the RNG for the dither is derived from the LSBs of the last N quantized words? The parity of the last few words as whole. That's because parity/xor has been proven to be an optimal randomness extractor in this sort of thing, and even if it doesn't remain so in the loop I just introduced, it's pretty much the only one which provably disregards both static leading and following zeroes. So that you can embed PCM words of any width, without having to tell how they were embedded, and still achieve in-even-hardware-low-cost synch. Don't say I never thought this out in full. ;) i think that if you cannot hear a different with a butt splice, you won't hear it with a cross fade. Definitely not true. Most means of interpolating over a splice repeat do not really do it over. They work fine within a running sample stream, but once they loop, they do something wrong. Especially at the very first nonrepeating run, and at the end of the last repeat. Or even if the interpolation algorithm is good enough, it's very difficult to make anybody else believe that it was so. Especially any naive listener who knows precious all of DSP and couldn't audit the code. All of the true, golden ears out there are like that. So... ;) if that were the case, Fletcher-Munson curves (or Robinson-Dadson, or pick your researcher) would have equal spacing for all frequencies. the fact that they get squished at the very low and very high frequencies is ostensibly not linear behavior. Of course. But then, this kind of a test shows that that human hearing has even a further, LTI-kinda-looking aspect, which doesn't have to do with those curves either. -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
Datapoint: I just tried repeating a ~1 sec brown noise clip in Audacity and I'm not sure if I get that choo choo effect. It sounds pretty continuous to me. However, I think this requires ABX testing in order to make sure. On Thu, May 8, 2014 at 8:14 PM, Nigel Redmon earle...@earlevel.com wrote: The 2-second area is my recollection as well, from when I played with noise sequence length, probably 20 years ago. Under 2, you don’t really have to pay attention to hear a repeat—your latches onto it easily—and as you get longer, you have to listen more carefully, and you get to the point quickly where you’re questioning yourself whether you’re hearing it repeat. The bottom line, I think, is that yes white noise is random, but the low frequency components are, well, low frequency. And it’s pretty each to pick out a repeating bump there. Not necessarily the bass end, more in the kids, and is probably a tradeoff between frequency and ear sensitivity. I just did a qd app, which generates 10 seconds of white noise, then adjusts the loop length as a percentage of the mouse vertical in the window, and start point based on horizontal position. Anyway, like I said, I’ve been through this before so there were no surprises. Sampo, were you looking for a particular revelation? I’m not sure if I’m listening for what you were getting at. On May 8, 2014, at 8:43 AM, STEFFAN DIEDRICHSEN sdiedrich...@me.com wrote: I bounced some 100 secs of noise taken from the test oscillator in Logic Pro. Loaded this in the IRU and did some cycling. My finding: There are portions in the noise, that allows me to go down to 2 seconds and it still sounded like straight (un-looped) noise. Other noise portions had “features”, that sounded like persons talking in the background or a squeak, or so. That’s so prominent, that it was easy to identify the cycle. Than, I did some experimentation, the IRU allows you to playback a selection in a cycle and the cycle can be dragged around without interrupting the playback. Doing that over a length of about 4 seconds with a 2 second long selection sounded to me like straight noise. Steffan On 08 May 2014, at 12:35, Sampo Syreeni de...@iki.fi wrote: Interestingly, nobody's taken the test as of yet. Even if it ain't in the least bit a contest, and I already said to begin with that the result might be rather interesting for any and all. -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
My two cents as a person in the field: the human hearing system is kind of an LTI... only at very low level processing. The consistency of measured signal (= perceiving the same signal the same way at all time as somebody wrote here) is present in the ear canal up to brainstem - inferior colliculus. But once we go to higher neuronal processing of auditory signals things get complicated and the same signal can be perceived in many different ways (e.g. google for top-down mechanism of auditory attention). The (non linear) fourier analysis and interpreting sounds as sinusoid are valid at ear canal level, and there are models with filterbanks to simulate that. But once we go to conscious perception (=cerebral cortex) evidence from animal research seems to point to a more complex analysis performed by the neurons: the so called spectro-temporal modulation (basically a 2D fourier transform). I.e. envelopes and phases are treated in different ways to identify sound objects. For those interested, this is a nice starting point (open access): http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003412#pcbi-1003412-g007 e. On Thu, May 8, 2014 at 8:28 AM, eric ericzh...@gmail.com wrote: It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. On 5/8/2014 1:25:28 AM, Sampo Syreeni de...@iki.fiwrote: On 2014-05-08, robert bristow-johnson wrote: there was a way that you could do subtractive dither in that the dither that you added before quantizing to a short word could be subtracted (to regain 4.77 dB) [...] I have some code for just that, even, and even better ideas. Maybe I even mentioned them somewhere a while back? If not, will fully share given interest. (The code is rather shitty, and even the ideas would benefit from development. But still better than you see implemented anywhere.) Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking about really is kind of interesting and unexpected, once you try it out on your own ears... when you loop the noise, is it a butt-splice? (i.e. no crossfade.) Yes. Otherwise the splice might introduce an interpolation artifact which would invalidate the experiment from the start. it's news to me that human hearing is LTI. Yes, well, it ain't. But even conventional psychophysical theory treats it as such. For example, why would we hear frequencies unless the ear was LTI? Fourier analysis, that is sinusoids as something special, doesn't make much sense unless you assume... Well, you know, at least something having to do with linearity and shift-variance... ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
As someone already pointed out, spend an evening to hack a website for this. Otherwise I just don’t feel like it’s worth the hassle, this is why-oh-why I don’t. Stefan On 08 May 2014, at 7:25 , Sampo Syreeni de...@iki.fi wrote: Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
I'd recommend Intelligence by Jeff Hawkins for some thought-provoking insights into high-level perceptual processing in the brain. Richard On 8 May 2014, at 06:59, Enr G e.glerean@gmail.com wrote: My two cents as a person in the field: the human hearing system is kind of an LTI... only at very low level processing. The consistency of measured signal (= perceiving the same signal the same way at all time as somebody wrote here) is present in the ear canal up to brainstem - inferior colliculus. But once we go to higher neuronal processing of auditory signals things get complicated and the same signal can be perceived in many different ways (e.g. google for top-down mechanism of auditory attention). The (non linear) fourier analysis and interpreting sounds as sinusoid are valid at ear canal level, and there are models with filterbanks to simulate that. But once we go to conscious perception (=cerebral cortex) evidence from animal research seems to point to a more complex analysis performed by the neurons: the so called spectro-temporal modulation (basically a 2D fourier transform). I.e. envelopes and phases are treated in different ways to identify sound objects. For those interested, this is a nice starting point (open access): http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003412#pcbi-1003412-g007 e. On Thu, May 8, 2014 at 8:28 AM, eric ericzh...@gmail.com wrote: It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. On 5/8/2014 1:25:28 AM, Sampo Syreeni de...@iki.fiwrote: On 2014-05-08, robert bristow-johnson wrote: there was a way that you could do subtractive dither in that the dither that you added before quantizing to a short word could be subtracted (to regain 4.77 dB) [...] I have some code for just that, even, and even better ideas. Maybe I even mentioned them somewhere a while back? If not, will fully share given interest. (The code is rather shitty, and even the ideas would benefit from development. But still better than you see implemented anywhere.) Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking about really is kind of interesting and unexpected, once you try it out on your own ears... when you loop the noise, is it a butt-splice? (i.e. no crossfade.) Yes. Otherwise the splice might introduce an interpolation artifact which would invalidate the experiment from the start. it's news to me that human hearing is LTI. Yes, well, it ain't. But even conventional psychophysical theory treats it as such. For example, why would we hear frequencies unless the ear was LTI? Fourier analysis, that is sinusoids as something special, doesn't make much sense unless you assume... Well, you know, at least something having to do with linearity and shift-variance... ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
If there, by chance, happens to be a feature in the noise that catches the ear and creates a sort of (possibly first subconscious) memory, then the choo-choo effect will be more audible as that feature can be more easily recognized again, reinforcing the memory. I generated 10 seconds of Gaussian white noise and can consistently recognize a certain short rhythmic feature from it. And, minutes after stopping playback, I can still recall that memory in my mind. It's even more easy to recognize the periodicity if you train your ears to recognize a shorter piece before playing back the whole (10 second or so) loop. So I think it boils down to two things: features and learning. Learning can also turn non-features into features. Sampo's test should be carried out multiple times to gather statistics, and because repetition will aid in reinforcement of the memory, also the number of repetitions should be controlled or recorded. How about tap to the rhythm of it? Feature-stripped noise should work better in some applications than truly random noise. Perhaps multi-band compression could be used to level it out. -olli On Thu, May 8, 2014 at 9:56 AM, Stefan Stenzel stefan.sten...@waldorfmusic.de wrote: As someone already pointed out, spend an evening to hack a website for this. Otherwise I just don’t feel like it’s worth the hassle, this is why-oh-why I don’t. Stefan On 08 May 2014, at 7:25 , Sampo Syreeni de...@iki.fi wrote: Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
On 2014-05-08, Olli Niemitalo wrote: Sampo's test should be carried out multiple times to gather statistics, and because repetition will aid in reinforcement of the memory, also the number of repetitions should be controlled or recorded. How about tap to the rhythm of it? Or, more to the point, you should always repeat the test using a different noise stream. You shouldn't be able to learn any statistical deviation from one test to another. The only learning and pattern recognition in play should take place from cycle to cycle, and possibly even so that you're limited from hearing more than two cycles of sequence. (Though it's pretty much impossible to implement that without the cutoff giving you a hint of what the repetition length was.) Interestingly, nobody's taken the test as of yet. Even if it ain't in the least bit a contest, and I already said to begin with that the result might be rather interesting for any and all. Feature-stripped noise should work better in some applications than truly random noise. Perhaps multi-band compression could be used to level it out. If you do anything of the sort, you by definition introduce structure into the signal. After that it ain't noise anymore. -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
It may be fine to think of the ear as doing a Fourier transform as a first, crude approximation. For a more accurate description however, some nonlinear effects would have to be considered. And some of this already happens in the ear. As for hearing being LTI, think about forward and backward masking. Although it happens at a rather short time scale, it implies that time invariance is not always the case. Harmonic distortion and intermodulation of two sinusoids played loudly enough also speaks against linearity. I haven't tried the experiment, but I recall a composer collegue once complaining about repetition in the noise generator of Csound. I think they used a random generator with period 2^16 in those days, but it's been improved now. Risto Holopainen -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
Small correction: the correct name is MM5837, which is a 16 bit shiftregister device. It’s bad but can be replaced by the MM5437, a 23 bit device which can be clocked externally and has a much longer period. Steffan On 08 May 2014, at 07:35, STEFFAN DIEDRICHSEN sdiedrich...@me.com wrote: The MN5837 is a pretty good noise source, if clocked externally. The internal clock is way too high and leads to audible periods. I used it in my thesis with good results. Steffan Von meinem iPhone gesendet Am 08.05.2014 um 06:51 schrieb Nigel Redmon earle...@earlevel.com: Reminds me…a few decades ago at Oberheim…Tom O. lamented to me bout a seemingly minor decision he’d made and later regretted…replacing an analog noise source with a digital noise generator (OBX—same in the Prophet 5). He took a bunch of grief from a guy who liked to meditate to noise, bought the OBX and was disappointed.You could hear the cycle pretty easily. -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
I bounced some 100 secs of noise taken from the test oscillator in Logic Pro. Loaded this in the IRU and did some cycling. My finding: There are portions in the noise, that allows me to go down to 2 seconds and it still sounded like straight (un-looped) noise. Other noise portions had “features”, that sounded like persons talking in the background or a squeak, or so. That’s so prominent, that it was easy to identify the cycle. Than, I did some experimentation, the IRU allows you to playback a selection in a cycle and the cycle can be dragged around without interrupting the playback. Doing that over a length of about 4 seconds with a 2 second long selection sounded to me like straight noise. Steffan On 08 May 2014, at 12:35, Sampo Syreeni de...@iki.fi wrote: Interestingly, nobody's taken the test as of yet. Even if it ain't in the least bit a contest, and I already said to begin with that the result might be rather interesting for any and all. -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
Does learning count as a non-linearity? Agus, T.R., Pressnitzer, D. (2013). The detection of repetitions in noise before and after perceptual learning. Journal of the Acoustical Society of America, 134(1), 464-473. http://lpp.psycho.univ-paris5.fr/abstract.php?id=3564 ...Diemo On 08.05.14 07:59, Enr G wrote: My two cents as a person in the field: the human hearing system is kind of an LTI... only at very low level processing. The consistency of measured signal (= perceiving the same signal the same way at all time as somebody wrote here) is present in the ear canal up to brainstem - inferior colliculus. But once we go to higher neuronal processing of auditory signals things get complicated and the same signal can be perceived in many different ways (e.g. google for top-down mechanism of auditory attention). The (non linear) fourier analysis and interpreting sounds as sinusoid are valid at ear canal level, and there are models with filterbanks to simulate that. But once we go to conscious perception (=cerebral cortex) evidence from animal research seems to point to a more complex analysis performed by the neurons: the so called spectro-temporal modulation (basically a 2D fourier transform). I.e. envelopes and phases are treated in different ways to identify sound objects. For those interested, this is a nice starting point (open access): http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003412#pcbi-1003412-g007 e. On Thu, May 8, 2014 at 8:28 AM, eric ericzh...@gmail.com wrote: It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. On 5/8/2014 1:25:28 AM, Sampo Syreeni de...@iki.fiwrote: On 2014-05-08, robert bristow-johnson wrote: there was a way that you could do subtractive dither in that the dither that you added before quantizing to a short word could be subtracted (to regain 4.77 dB) [...] I have some code for just that, even, and even better ideas. Maybe I even mentioned them somewhere a while back? If not, will fully share given interest. (The code is rather shitty, and even the ideas would benefit from development. But still better than you see implemented anywhere.) Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking about really is kind of interesting and unexpected, once you try it out on your own ears... when you loop the noise, is it a butt-splice? (i.e. no crossfade.) Yes. Otherwise the splice might introduce an interpolation artifact which would invalidate the experiment from the start. it's news to me that human hearing is LTI. Yes, well, it ain't. But even conventional psychophysical theory treats it as such. For example, why would we hear frequencies unless the ear was LTI? Fourier analysis, that is sinusoids as something special, doesn't make much sense unless you assume... Well, you know, at least something having to do with linearity and shift-variance... ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- Diemo Schwarz, PhD -- http://diemo.concatenative.net Sound–Music–Movement Interaction Team -- http://ismm.ircam.fr IRCAM - Centre Pompidou -- 1, place Igor-Stravinsky, 75004 Paris, France Phone +33-1-4478-4879 -- Fax +33-1-4478-1540 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
On Thu, May 8, 2014 at 12:59 AM, Enr G e.glerean@gmail.com wrote: My two cents as a person in the field: the human hearing system is kind of an LTI... LTI is a very specific thing. It's not sort of, kind of, LTI--it's just either LTI or not. only at very low level processing. The consistency of measured signal (= perceiving the same signal the same way at all time as somebody wrote here) is present in the ear canal up to brainstem - inferior colliculus. No, it's not. LTI means always stationary. Two easy ones that originate from the named region: 1. Stapedius response 2. Tinnitus I agree with the sentiment: There are multiple concurrent representations of sound, and at some level of auditory processing, sounds are frequently represented the same way. but it's not LTI--you have to ignore a lot of things to treat your auditory system as approximately LTI But once we go to higher neuronal processing of auditory signals things get complicated and the same signal can be perceived in many different ways (e.g. google for top-down mechanism of auditory attention). The (non linear) fourier analysis and interpreting sounds as sinusoid are valid at ear canal level, and there are models with filterbanks to simulate that. But once we go to conscious perception (=cerebral cortex) evidence from animal research seems to point to a more complex analysis performed by the neurons: the so called spectro-temporal modulation (basically a 2D fourier transform). I.e. envelopes and phases are treated in different ways to identify sound objects. For those interested, this is a nice starting point (open access): http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003412#pcbi-1003412-g007 Looks good--I read some very good articles from almost a decade ago (sigh) about the planum temporale (posterior temporal gyrus, right?). The Robert Zatorre articles on this topic were my favorite ones. e. On Thu, May 8, 2014 at 8:28 AM, eric ericzh...@gmail.com wrote: It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. On 5/8/2014 1:25:28 AM, Sampo Syreeni de...@iki.fiwrote: On 2014-05-08, robert bristow-johnson wrote: there was a way that you could do subtractive dither in that the dither that you added before quantizing to a short word could be subtracted (to regain 4.77 dB) [...] I have some code for just that, even, and even better ideas. Maybe I even mentioned them somewhere a while back? If not, will fully share given interest. (The code is rather shitty, and even the ideas would benefit from development. But still better than you see implemented anywhere.) Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking about really is kind of interesting and unexpected, once you try it out on your own ears... when you loop the noise, is it a butt-splice? (i.e. no crossfade.) Yes. Otherwise the splice might introduce an interpolation artifact which would invalidate the experiment from the start. it's news to me that human hearing is LTI. Yes, well, it ain't. But even conventional psychophysical theory treats it as such. For example, why would we hear frequencies unless the ear was LTI? Fourier analysis, that is sinusoids as something special, doesn't make much sense unless you assume... Well, you know, at least something having to do with linearity and shift-variance... ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. One of the easiest ways to see that hearing must be nonlinear is to think about masking effects. In isolation, a signal will sound like one thing. But if you add another signal to it, then the sum will not sound like the sum of the two signals (generally). One of the signals may even disappear from your perception entirely! So, this can't be the product of a linear system. Also, you don't necessarily perceive the same signal the same way at all times (even ignoring aging, etc.). This is relevant to Sampo's loop experiment, actually. Take a loop of sound (any sound), say 1-2 seconds in length, and listen to it for a long time (say 1 minute or more). You'll find that after a while weird things happen to your perception of the sound, with some components seeming to move in and out of phase with others and so on. Which doesn't sound like a time-invariant system to me! E On Wed, May 7, 2014 at 10:28 PM, eric ericzh...@gmail.com wrote: It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. On 5/8/2014 1:25:28 AM, Sampo Syreeni de...@iki.fiwrote: On 2014-05-08, robert bristow-johnson wrote: there was a way that you could do subtractive dither in that the dither that you added before quantizing to a short word could be subtracted (to regain 4.77 dB) [...] I have some code for just that, even, and even better ideas. Maybe I even mentioned them somewhere a while back? If not, will fully share given interest. (The code is rather shitty, and even the ideas would benefit from development. But still better than you see implemented anywhere.) Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking about really is kind of interesting and unexpected, once you try it out on your own ears... when you loop the noise, is it a butt-splice? (i.e. no crossfade.) Yes. Otherwise the splice might introduce an interpolation artifact which would invalidate the experiment from the start. it's news to me that human hearing is LTI. Yes, well, it ain't. But even conventional psychophysical theory treats it as such. For example, why would we hear frequencies unless the ear was LTI? Fourier analysis, that is sinusoids as something special, doesn't make much sense unless you assume... Well, you know, at least something having to do with linearity and shift-variance... ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
the human hearing system is kind of an LTI... only at very low level processing. The consistency of measured signal (= perceiving the same signal the same way at all time as somebody wrote here) is present in the ear canal up to brainstem - inferior colliculus. My understanding is that there are measurable nonlinear effects even in the cochlea. Apparently when a loud frequency is present that excites one region of the membrane, the surrounding fibers react to dampen nearby sound and reinforce the purity of the dominant frequency. The pithy way of phrasing this is the frequency response of the ear of a dead cat is different from that of a live cat. Not sure if anybody actually did that exact experiment to verify that... Of course, that doesn't invalidate the same sound sounds the same later property, but if you ask me that's a much much broader thing than LTI. For example, any static nonlinearity - no matter how extreme and nonlinear - will always produce the same output given the same input. That doesn't mean it's linear, it just means it's time-invariant. E E On Wed, May 7, 2014 at 10:59 PM, Enr G e.glerean@gmail.com wrote: My two cents as a person in the field: the human hearing system is kind of an LTI... only at very low level processing. The consistency of measured signal (= perceiving the same signal the same way at all time as somebody wrote here) is present in the ear canal up to brainstem - inferior colliculus. But once we go to higher neuronal processing of auditory signals things get complicated and the same signal can be perceived in many different ways (e.g. google for top-down mechanism of auditory attention). The (non linear) fourier analysis and interpreting sounds as sinusoid are valid at ear canal level, and there are models with filterbanks to simulate that. But once we go to conscious perception (=cerebral cortex) evidence from animal research seems to point to a more complex analysis performed by the neurons: the so called spectro-temporal modulation (basically a 2D fourier transform). I.e. envelopes and phases are treated in different ways to identify sound objects. For those interested, this is a nice starting point (open access): http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003412#pcbi-1003412-g007 e. On Thu, May 8, 2014 at 8:28 AM, eric ericzh...@gmail.com wrote: It would appear to me that the human hearing system is an LTI system. It doesn't react in a linear fashion to frequency or loudness, but it perceives the same signal the same way at all times, disregarding aging, hearing loss, etc. On 5/8/2014 1:25:28 AM, Sampo Syreeni de...@iki.fiwrote: On 2014-05-08, robert bristow-johnson wrote: there was a way that you could do subtractive dither in that the dither that you added before quantizing to a short word could be subtracted (to regain 4.77 dB) [...] I have some code for just that, even, and even better ideas. Maybe I even mentioned them somewhere a while back? If not, will fully share given interest. (The code is rather shitty, and even the ideas would benefit from development. But still better than you see implemented anywhere.) Yet why-oh-why doesn't anybody just pop up their Audacity and a few megabytes of randomness, the way I originally asked? Because the stuff I'm talking about really is kind of interesting and unexpected, once you try it out on your own ears... when you loop the noise, is it a butt-splice? (i.e. no crossfade.) Yes. Otherwise the splice might introduce an interpolation artifact which would invalidate the experiment from the start. it's news to me that human hearing is LTI. Yes, well, it ain't. But even conventional psychophysical theory treats it as such. For example, why would we hear frequencies unless the ear was LTI? Fourier analysis, that is sinusoids as something special, doesn't make much sense unless you assume... Well, you know, at least something having to do with linearity and shift-variance... ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links
Re: [music-dsp] a weird but salient, LTI-relevant question
Having quickly browsed over this subject, think about it that it normally isn't needed to do more than be accurate enough when dealing with audio and the human hearing, unless you want to explicitly deal with Loudness Curve sensitivity, or exotic subjects like creating stereo images for cinema! Mathematically Linear and Time Invariance is usually needed for certain (important) classes of Differential Equations, and of course usually a desirable property for a lot of types of equipment dealing with signals. About the noise, I'll say it only one time: IS YOUR NOISE SOURCE BANDWIDTH LIMITED, and it so (important undergrad EE question, seriously): how ? I mean going to things like Gaussian Distributions goes deeper than most here will want to (or can) go, and I don't see the point of it much, unless it is made more specific what that is for. T. -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
What is this LTI theory of human hearing you speak of? -- eric zhang Sent with Sparrow (http://www.sparrowmailapp.com/?sig) On Wednesday, May 7, 2014 at 8:39 PM, Sampo Syreeni wrote: This is going to sound pretty weird, I'm sure, but could as many people on-list perform the following experiment on themselves and their close ones, as possible? Then report back (privately, so as not to ruin the surprise for everybody else?) Take a long (at least 30 seconds and possibly more) sequence of truly random (AWGN) noise, either from a very long period PRNG or from a primary randomness source. Then starting with very long periods of over 10 seconds, loop the noise, curtailing the period of repetition. Dropping it, say, 200ms at a time at first, and in the end perhaps something like 10ms at a time. When does your ear, perceptually speaking, start to say that the noise repeats? Precisely? I'd be interested in hearing what people on-list have to say about this one. Especially the ones who are curious enough to find the precise limit in milliseconds, and even subject their loved ones to the test. Because, I mean, at least for me this was a total mindfuck, and if you analyze it e.g. via the usual LTI theory of human hearing, the results do not make any sense at all. I think, but I'm not too sure. Whence the question. ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
With some of the modern web technologies (esp WebAudio API), such an experiment could be easily deployed onto a web-page, with users inputting their answers into the page to be processed analyzed. Just an idea. -Chinmay On Thu, May 8, 2014 at 8:39 AM, Sampo Syreeni de...@iki.fi wrote: Take a long (at least 30 seconds and possibly more) sequence of truly random (AWGN) noise, either from a very long period PRNG or from a primary randomness source. Then starting with very long periods of over 10 seconds, loop the noise, curtailing the period of repetition. Dropping it, say, 200ms at a time at first, and in the end perhaps something like 10ms at a time. When does your ear, perceptually speaking, start to say that the noise repeats? Precisely? -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
Should standardize the sampling rate as well. With an infinite sampling rate and your method, you'd have something like a pure broadband tone, right? On May 7, 2014, at 5:39 PM, Sampo Syreeni de...@iki.fi wrote: This is going to sound pretty weird, I'm sure, but could as many people on-list perform the following experiment on themselves and their close ones, as possible? Then report back (privately, so as not to ruin the surprise for everybody else?) Take a long (at least 30 seconds and possibly more) sequence of truly random (AWGN) noise, either from a very long period PRNG or from a primary randomness source. Then starting with very long periods of over 10 seconds, loop the noise, curtailing the period of repetition. Dropping it, say, 200ms at a time at first, and in the end perhaps something like 10ms at a time. When does your ear, perceptually speaking, start to say that the noise repeats? Precisely? I'd be interested in hearing what people on-list have to say about this one. Especially the ones who are curious enough to find the precise limit in milliseconds, and even subject their loved ones to the test. Because, I mean, at least for me this was a total mindfuck, and if you analyze it e.g. via the usual LTI theory of human hearing, the results do not make any sense at all. I think, but I'm not too sure. Whence the question. ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
Re: [music-dsp] a weird but salient, LTI-relevant question
I've never heard this phenomenon myself, but I am familiar with it. It is a psychoacoustic phemonen, and I've heard it referred to as choo-chooing, though when I just googled for that I got nothing related, so maybe that's just a colloquial term amongst the engineers I know. I've never come across it in any of textbooks on the subject, though I'm sure there are papers written about it. Some early hardware dithers found it cheaper to store a table of numbers in ROM than to calculate random numbers with a PRNGs [1]. Because memory was so expensive at the time, the length of the loop was chosen to be just long enough to avoid the Choo-Chooing phenomenon. If I remember correctly from what the designer of one of those dithers told me, the length of repeat that causes choo-chooing is very nearly the same for everyone, so it was pretty each to choose the appropriate loop length. It would be cool to have a WebAudio demonstration and/or test of this, as Chinmay Pendharkar suggested. bjorn [1] You may have noticed early dithers made vague and strange marketing claims. Like, this is not a real dither, but a signal, or not a dither, but a bitmapping/bit-reduction scheme or that they were somehow different from or better than dither, even though the effect is exactly the same (or, if anything, arguably worse, because no engineer with access to a halfway decent PRNG would use a LUT). How the marketing departments of these companies managed to turn the liability of not having a PRNG into an asset is just proof that the marketing departments of these companies are a bunch of mindless jerks who'll be the first against the wall when the revolution comes. On Wed, May 7, 2014 at 10:10 PM, Eden Sherry e...@eden2.com wrote: Should standardize the sampling rate as well. With an infinite sampling rate and your method, you'd have something like a pure broadband tone, right? On May 7, 2014, at 5:39 PM, Sampo Syreeni de...@iki.fi wrote: This is going to sound pretty weird, I'm sure, but could as many people on-list perform the following experiment on themselves and their close ones, as possible? Then report back (privately, so as not to ruin the surprise for everybody else?) Take a long (at least 30 seconds and possibly more) sequence of truly random (AWGN) noise, either from a very long period PRNG or from a primary randomness source. Then starting with very long periods of over 10 seconds, loop the noise, curtailing the period of repetition. Dropping it, say, 200ms at a time at first, and in the end perhaps something like 10ms at a time. When does your ear, perceptually speaking, start to say that the noise repeats? Precisely? I'd be interested in hearing what people on-list have to say about this one. Especially the ones who are curious enough to find the precise limit in milliseconds, and even subject their loved ones to the test. Because, I mean, at least for me this was a total mindfuck, and if you analyze it e.g. via the usual LTI theory of human hearing, the results do not make any sense at all. I think, but I'm not too sure. Whence the question. ;) -- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-40-3255353, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp -- - Bjorn Roche bjornroche.com http://blog.bjornroche.com @xonamiaudio -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
