So, for the love of the flying spaghetti monster, could you please finally answer these simple questions amirm?

No, I started up pretty "deaf."  I remember being shocked that I could not hear much difference between 128 kbps MP3 and the source.  That bothered me .  So I started on a path to become a trained listener and after literally hundreds of hours of testing, and tons of education learning about psychoacoustics and algorithms in audio processing, all of a sudden found myself in a super unique situation of outperforming everyone else around me in such tests.  I have never liked the phrase but everyone would call me the "golden ear."

And let's distinguish between hearing and listening.  My hearing is shot due to age.  I am embarrassed to say that I can't even hear 12 Khz well.  The reason I do well still I think is that I focus on what I think technically matter and combine that with my training to look for small differences.  I suspect people with my training but intact frequency response will be able to do a lot better.  I actually ran into one such person at Microsoft who was working with a partner of ours.  He was hearing high frequency distortions I could not.  We hired him immediately .  And I moved off from doing a lot of the listening tests myself.

Let me confess.  I had no idea I could do this after so many years after retirement. I just ran the tests because people like Arny kept egging me on so I gave it a try.

Quote from: amirm on 2014-11-19 18:54:40

[...]
Having read the Stuart paper and prior citations, I am starting to think this may be due to time domain impact.  It certainly is not frequency domain since I can't hear the ultrasonics. Just as pre-echo is a very audible time domain artifact (although created in frequency domain), maybe these filters act the same way.

After reading this I get an even stronger sense that you must have been cheating in a lot of the logs you posted, or you have some seriously anomalous hearing (regarding detecting lossy compression).

The filters used have linear phase. The pre-echo is no echo but filter ringing at over 21 kHz that only acts on the energy that is up there.
If you can't hear well past 12 kHz then how would you detect the ringing of a filter at over 21 kHz? So please explain why this filter ringing is of concern for you.

Applying the same analysis to the sharp cut-off filter that was tested in the listening test gives us 9.5-2.5 = 7 milliseconds.  In other words the span of ringing is now about 5 times wider in time than it was in the short cut off.

Is this audible?  I gave a reference in my post as to how it might be: pre-echo.  In psychoacoustics there is a concept of temporal masking.  If you hear a loud sound, what follows it very quickly may not be audible.  So if we look at our impulse itself, it creates a pretty nice shadow over what is to follow it.  But looking behind it, there is impulse (assuming silence for now) and backward temporal masking is quite limited.  This could, could, make the pre-ringing audible.

Note that since this is in time domain, it has nothing to do with my ability to hear high frequencies.

All audio samples go through the above transformation, not just high frequency ones.  My truncated frequency response has no bearing on this situation unless the test tones are only above my hearing which is not the case in this musical segment.  I am pretty sure I can hear what music is playing .

As I'm sure you know, Bob will sell you one on the playback side. It'll cut so early (18kHz IIRC) and gently that it will removing all that nasty 22kHz ringing, even if it's in the source.

Tell me again why you guys are arguing.

I have a much easier solution that doesn't require new hardware from anyone: get the high sampling rate version of the content.  Problem solved.  You all can do the same if you choose.  Tell me again why you guys are arguing.

P.S. You've got 3kHz between 19kHz and 22kHz with CD's 44.1kHz sampling. You can have your gentle filter. As I'm sure you know, Bob will sell you one on the playback side. It'll cut so early (18kHz IIRC) and gently that it will removing all that nasty 22kHz ringing, even if it's in the source.

The above is also the reason I say that if CD had picked 48 Khz as the sampling, I would have no beef with it.  We have plenty of room to implement our filter above 20 Khz. But by picking 44.1, it leaves us a small margin forcing sharper filters and more time domain ringing.

Quote from: amirm on 2014-11-21 17:11:16

Tell me again why you guys are arguing.

Again?! Isn't 18 pages of it sufficient?

Quote from: amirm on 2014-11-21 17:11:16

I have a much easier solution that doesn't require new hardware from anyone: get the high sampling rate version of the content.  Problem solved.  You all can do the same if you choose.  Tell me again why you guys are arguing.

The false puffiness over the fear that SRCs will cause audible artifacts in 5 of 9 attempts under specific criteria, when far larger issues remain unresolved in the process as they relate to what is actually provided to the buying public?

I am simply avoiding the problem altogether.

For CD that conversion is mandatory since the format requires.

Quote from: amirm on 2014-11-21 17:11:16

I have a much easier solution that doesn't require new hardware from anyone: get the high sampling rate version of the content.  Problem solved.  You all can do the same if you choose.  Tell me again why you guys are arguing.

The false puffiness over the fear that SRCs will cause audible artifacts in 5 of 9 attempts under specific criteria, when far larger issues remain unresolved in the process as they relate to what is actually provided to the buying public?

With digital distribution there is no such restriction so we can and are getting the pre-converted bits.

It is a shame though that I can't get people to agree with the simple business principal that high resolution downloads are happening.

Quote from: greynol on 2014-11-21 17:23:14

Quote from: amirm on 2014-11-21 17:11:16

I have a much easier solution that doesn't require new hardware from anyone: get the high sampling rate version of the content.  Problem solved.  You all can do the same if you choose.  Tell me again why you guys are arguing.

The false puffiness over the fear that SRCs will cause audible artifacts in 5 of 9 attempts under specific criteria, when far larger issues remain unresolved in the process as they relate to what is actually provided to the buying public?

For reasons we can only speculate about,  Stuart and the hi rez cheerleading squad (which maybe should be rebranded as the Redbook Fearmongering Corps)  would rather focus on eliminating the ant in the room.  It's odd because surely there is money in upgraded *mastering* and in *room treatment/correction*,  things which would address the real problems with modern home audio.

It appears there is no need to speculate because the AES is working with the industry to bring hi-res to market. Consider the following two links:

http://www.aes.org/events/137/press/?ID=265
http://www.aes.org/events/137/specialevents/?ID=4222

The answer is right in what I wrote but since it was misunderstood, I am going to explain the basics.

What you describe is not "ringing" but passband ripple.

Yes, it is sometimes called ringing but given the fact that I was talking about time domain (see the new highlight in red), you shouldn't have gone to frequency domain.

There is no disagreement there.  The paper makes it clear and I have said the same that the filters are near perfect in frequency domain:

For both FIR lters, the ripple depth over the passband was a maximum of 0.025 dB, and the stopband attenuation was 90 dB.

Note the correct terminology of "ripple" not ringing.  But yes, that is as ruler flat as we need it with just +-.025db variation and aliasing truncated by 90 db.  I wouldn't be able to hear that 0.025 db variation if it were in the range that I can hear.  And this as you say is in the range that I can't hear.  So again, no disagreement that that the frequency domain analysis doesn't indicate why this could be audible.

What followed in my post was a hypothesis.  It is a hypothesis that is stated in the paper as I indicated.  As any hypothesis, it is being offered as a potential answer, not proof.  There is foundation in it but not one that I have personally investigated and hence the phrase I used: "I am starting to think..."

What is that thinking?  It is what I described.  What is happening in time domain.  I created two filters in Matlab using the same 0.025 db passband ripple and 90 db out of band rejection.  The first one is very similar to what Stuart used in his study (not identical because I am not performing any optimization):

{img}

This is for the 48k sampling case.  We are filtering everything above 24 Khz and starting to do that at 23.5 Khz as the paper mentions.  This is not the frequency domain response which would be boring in its flatness as described above and in your post.  But rather the impulse response of the filter. 

Now we see "ringing."  The center is our signal that we fed to the filter (a sharp spike).  What we have now is pre- and post-ringing.  The impulse is replicated prior to its appearance (pre-ringing) and after its appearance.  The math dictates that it behave this way.  Indeed this is a computer simulation based on the mathematics of the signal processing.

Before I say more, let's look at the same filter, but this time we relax the constraints so that the filtering starts at 21 Khz instead of 23.5.  In other words, instead of giving the filter just 500 Hz to go from max to -90 db, we give it 3,000 Hz to do the same.  The picture changes dramatically:

{img}

Don't worry about the details of the graph.  The scales are different so this one is much more magnified.  Pay attention to red arrows here and in the previous graphs.  In this instantiation, ringing substantially subsides 0.2 milliseconds and 1.7 milliseconds.  So the difference is roughly 1.5 milliseconds.  This is the duration of our "distortion" if you will.

Applying the same analysis to the sharp cut-off filter that was tested in the listening test gives us 9.5-2.5 = 7 milliseconds.  In other words the span of ringing is now about 5 times wider in time than it was in the short cut off.

Is this audible?  I gave a reference in my post as to how it might be: pre-echo.  In psychoacoustics there is a concept of temporal masking.  If you hear a loud sound, what follows it very quickly may not be audible.  So if we look at our impulse itself, it creates a pretty nice shadow over what is to follow it.  But looking behind it, there is impulse (assuming silence for now) and backward temporal masking is quite limited.  This could, could, make the pre-ringing audible.

Note that since this is in time domain, it has nothing to do with my ability to hear high frequencies.  All audio samples go through the above transformation, not just high frequency ones.  My truncated frequency response has no bearing on this situation unless the test tones are only above my hearing which is not the case in this musical segment.  I am pretty sure I can hear what music is playing .

The way you refer to pre-echo as "not being an echo" is totally nonsensical.  Of course it is not an echo.  It is *pre*-echo as it happens prior to the signal itself.

The psychoacoustic component of the effect is that one hears only the echo preceding the transient, not the one following – because this latter is drowned out by the transient. Formally, forward temporal masking is much stronger than backwards temporal masking, hence one hears a pre-echo, but no post-echo.

It did it again! 

And by downloading such bits I am free of worrying whether downgrading them is audible or not.

It appears there is no need to speculate because the AES is working with the industry to bring hi-res to market. Consider the following two links:

http://www.aes.org/events/137/press/?ID=265
http://www.aes.org/events/137/specialevents/?ID=4222

Then take a look how Sony is marketing it.

http://discover.store.sony.com/High-Resolution-Audio/

Discover subtle details and artistic nuances in your favorite
music that you’ve never heard before. Feel the power
and presence of a live performance in your living room.
Or experience what it’s like to sit in on a live studio recording.
It’s all possible with the superior quality of High-Resolution Audio.
With quality greatly surpassing that of MP3 and CD, the difference is clear.

Quote from: amirm on 2014-11-21 17:52:42

And by downloading such bits I am free of worrying whether downgrading them is audible or not.

There is some logic in there. There is also some logic in capturing the microphone output as losslessly as possible, even if we can't hear it. DXD looks like a safe format for that, since most microphones don't have a bandwidth of more than 100 kHz. Higher-res downloads are more expensive and the claim is that the higher the bitrate, the better the sound quality. From older papers I got the impression that Bob Stuart seems to think that audible differences disappear above 24/96. Besides the satisfaction of "having the studio quality", what would be the point of buying higher formats ?

It has further been suggested [22, 23, 24] that listeners can discriminate timing differences of the order of 5 µs and below, which, if correct, would require a Nyquist frequency of 32 kHz or higher...

However, it can not be assumed that the auditory system cannot extract time differences that are shorter than the periods between successive samples, even when convolved with a sinc function in D/A conversion (assuming a sufficient signal-to-noise ratio).