The HD-Audio Challenge II

[Pim]

 Are my ears up to it? Probably not. 

Hi res music has the technical capacity to produce frequencies above red book CD quality, which is about 22 kHz. That's the one and only difference between CD and Hi res. Anything above 20 kHz or so is beyond the scope of human hearing so to answer your question; nope, and neither are anyone else's.

i have read this claim many times and it seems reasonable.

However I, and quite a few people I have spoken to, can definitely hear ultrasonic catstoppers that, as far as i could check are typically specced at 23 khz.

i am not sure what to make out of this.

Cheers,
Bernard

I used to be able to too but there's no music at that frequency.

[Jean-Marie]

23kHz is possible if you are very young and that it is very loud.

This is also quite dangerous because the frequency limits are define as the point where you threshold of audition equals the threshold of pain.

We also need to ensure that the systems are perfectly linear. Too many systems, when trying to reproduce ultrasonic frequencies have non linearities that produces sub harmonics down in the audio band.

Jean-Marie

[David A]

 Are my ears up to it? Probably not. 

Hi res music has the technical capacity to produce frequencies above red book CD quality, which is about 22 kHz. That's the one and only difference between CD and Hi res. Anything above 20 kHz or so is beyond the scope of human hearing so to answer your question; nope, and neither are anyone else's.

i have read this claim many times and it seems reasonable.

However I, and quite a few people I have spoken to, can definitely hear ultrasonic catstoppers that, as far as i could check are typically specced at 23 khz.

i am not sure what to make out of this.

Cheers,
Bernard

Unless you're under 20 years of age I can pretty well assure you that you can't hear 23 kHz. I don't know what kind of a signal catstoppers put out but something may be audible.

One of our common audio specifications is for intermodulation distortion. If you have 2 tones at different frequencies, they generate distortion at frequencies which are multiples of the difference in frequency of the 2 tones. The standard test for intermodulation distortion is to use a test signal comprised of tones at 19 kHz and 20 kHz respectively and both of those frequencies are beyond the hearing range of most people out of their teens, probably out of the range of most teenagers as well unless they've managed to avoid listening to music at loud levels. The distortion products occur at 1 kHz, the difference between the 2 tones, and at multiples of 1 kHz. While we can't hear the 19 kHz and 20 kHz tones, if they are loud enough we can hear the distortion tones at 1 kHz and it's multiples that lie within our hearing range. If your catstopper uses two or more tones to deter cats then while you may not be able to hear the tones it uses, you may well be able to hear the intermodulation distortion tones that are generated.

Such tones actually sound quite strange. I have a recording by an avant grade performance artist named Meredith Monk. One track consists of her creating a high frequency tone by running her wet finger around the rim of a crystal glass, generating a high pitched tone caused by exciting the resonance of the glass. At the same time she starts singing a note just above the frequency of the tone generated by the glass and slowly drops the pitch of her sung note to below that of the tone generated by the glass, then brings her note back up to above that of the glass and then down again, and simply keeps repeating this process for a couple of minutes. What you hear while listening to this track are the sounds of the glass and of the voice where you would expect to hear them in the soundstage but at the same time you hear a slowly changing rather piercing tone in your ears, the sound of the varying difference in frequencies between Monk's voice and the resonance of the glass, an intermodulation product. It's actually surprisingly loud and it tends to "drive people crazy" as the saying goes. Any time I play that track to someone it's almost guaranteed to generate a "take that damn thing off!" response because the intermodulation tone which sounds like it's located inside your ears is so annoying. Strangely, it's not a low pitched sound which you would expect because the difference in frequency between the voice and the wine glass resonance is quite small, but a rather high pitched sound, a multiple of the difference between the 2 actual sounds on the recording. The reason it appears to come from a location within your ears is probably because one of the higher intermodulation products is actually exciting a standing wave resonance within your ear canal and the pitch is high because the physical length of the air column being excited in your ear canal is very short. I think part of the annoyance also comes because the resonance actually causes a slight physical vibration within the ear which is also unpleasant.

As I said, i don't know what the signal catstoppers put out is like but just if it's above the range of your hearing that doesn't necessarily mean that you won't hear anything while it's working. If it's emitting 2 or more tones simultaneously you may quite possibly be hearing the sound of the intermodulation products created by those tones because the intermodulation products are within your hearing range while the actual tones generating them are not.

[bernardl]

Very interesting David, thanks for sharing.

So I may not be super human after all. :-(

Cheers,
Bernard

[Axel]

Hi res music has the technical capacity to produce frequencies above red book CD quality, which is about 22 kHz. That's the one and only difference between CD and Hi res. Anything above 20 kHz or so is beyond the scope of human hearing so to answer your question; nope, and neither are anyone else's.

i have read this claim many times and it seems reasonable.

However I, and quite a few people I have spoken to, can definitely hear ultrasonic catstoppers that, as far as i could check are typically specced at 23 khz.

i am not sure what to make out of this.

Cheers,
Bernard

Unless you're under 20 years of age I can pretty well assure you that you can't hear 23 kHz. I don't know what kind of a signal catstoppers put out but something may be audible.

One of our common audio specifications is for intermodulation distortion. If you have 2 tones at different frequencies, they generate distortion at frequencies which are multiples of the difference in frequency of the 2 tones. The standard test for intermodulation distortion is to use a test signal comprised of tones at 19 kHz and 20 kHz respectively and both of those frequencies are beyond the hearing range of most people out of their teens, probably out of the range of most teenagers as well unless they've managed to avoid listening to music at loud levels. The distortion products occur at 1 kHz, the difference between the 2 tones, and at multiples of 1 kHz. While we can't hear the 19 kHz and 20 kHz tones, if they are loud enough we can hear the distortion tones at 1 kHz and it's multiples that lie within our hearing range. If your catstopper uses two or more tones to deter cats then while you may not be able to hear the tones it uses, you may well be able to hear the intermodulation distortion tones that are generated.

Such tones actually sound quite strange. I have a recording by an avant grade performance artist named Meredith Monk. One track consists of her creating a high frequency tone by running her wet finger around the rim of a crystal glass, generating a high pitched tone caused by exciting the resonance of the glass. At the same time she starts singing a note just above the frequency of the tone generated by the glass and slowly drops the pitch of her sung note to below that of the tone generated by the glass, then brings her note back up to above that of the glass and then down again, and simply keeps repeating this process for a couple of minutes. What you hear while listening to this track are the sounds of the glass and of the voice where you would expect to hear them in the soundstage but at the same time you hear a slowly changing rather piercing tone in your ears, the sound of the varying difference in frequencies between Monk's voice and the resonance of the glass, an intermodulation product. It's actually surprisingly loud and it tends to "drive people crazy" as the saying goes. Any time I play that track to someone it's almost guaranteed to generate a "take that damn thing off!" response because the intermodulation tone which sounds like it's located inside your ears is so annoying. Strangely, it's not a low pitched sound which you would expect because the difference in frequency between the voice and the wine glass resonance is quite small, but a rather high pitched sound, a multiple of the difference between the 2 actual sounds on the recording. The reason it appears to come from a location within your ears is probably because one of the higher intermodulation products is actually exciting a standing wave resonance within your ear canal and the pitch is high because the physical length of the air column being excited in your ear canal is very short. I think part of the annoyance also comes because the resonance actually causes a slight physical vibration within the ear which is also unpleasant.

As I said, i don't know what the signal catstoppers put out is like but just if it's above the range of your hearing that doesn't necessarily mean that you won't hear anything while it's working. If it's emitting 2 or more tones simultaneously you may quite possibly be hearing the sound of the intermodulation products created by those tones because the intermodulation products are within your hearing range while the actual tones generating them are not.

What’s the name of the Meredith Monk track, please @David A

[David A]

Very interesting David, thanks for sharing.

So I may not be super human after all. :-(

Cheers,
Bernard

Sadly none of us are superhuman but there's a lot about being a normal human that we can be unaware of. There's a lot of interesting things about how we can't hear things we can normally expect to hear because of other sounds in the environment (masking) and about being able to hear things we don't expect to hear for other reasons. The usually accepted "fact" that we can hear from 20 Hz to 20 kHz is a fact that comes with a hell of a lot of qualifications and exceptions buried in the small print that we never bother to read.

[David A]

@Axel,

Do you really want to go there? :-)

The track is called "Slide" and it's on Monk's "Our Lady of Late" album from 1973. It is available on Tidal.

I had to dig the CD out of my collection in order to find the track again, I haven't played that album in years. Just for the hell of it, I put it on again. A couple of decades since I last heard it and the combination of 20 year old ears and the tinnitus I didn't have back then seem to have rendered me immune to the intermodulation tone. I could no longer hear it and I'm surprised to say that I missed it. I think it is an intended part of the experience and it looks like it is now denied me.

[Snoopy8]

There did not seem to be much interest in this one, only three of us by the look of it, but maybe some other forums members had a go?  (and if you didn't try the test, the original test files are still available for download - something to try whilst stuck at home?)

Anyway, the initial results have been released.  As a brief summary, typically those that tried the test found little or no difference between the native 24/96 versions and the down sampled 16/44.1 versions.

I tried and failed to tell the difference, getting 9 out of 20! Not unexpected from previous comparisons, but this was useful because I thought I had better system now and with more experience. WRONG!  I was no better than picking randomly.

For me, I found performing the test both interesting and enlightening, and the initial results are an interesting read too.  I have always been of the view that the quality of the mastering massively trumps the actual file delivery format, and my experience from this test tells me that anything above 16/44.1 is bordering on being irrelevant.  Controversial I know! 

I agree that better mastering trumps higher bit rate, bit depth. The problem is that often the better master is only available on hi res only and/or in SACDs. And not all new masters are better.

[f1eng]

I did it. I didn't audition all the tracks since those I liked I didn't hear a difference.
This is the same as last time I tried it independently where I got a friend to produce 2 identical size files, one 24/96 original recording and the second the same file downsampled to 16/44.1 then back to 24/96.
That means without cheating and using software to examine the files one knows started the same, the DAC will treat them the same but one contains no data over and above a CD.
I heard no difference then either.
OTOH as far as I can see there is nothing audible in music that isn't perfectly recorded by 44.1/16 as long as the recording is done correctly so any difference one actually hears implies a different mix rather than a difference between 24/96 and 16/44.1

[ogs]

I am still quite confident that wide bandwidth makes a difference. No one (or extremely few) can hear above 17 to 20 kHz, but David's tale of intermodulation gives us a clue. Research has shown (I know I should reference this, but the closest I get at the moment is that the experiments were done in Japan many years ago) that listeners can discern a difference when tones above 20kHz are played in stereo and switched off and on, even if they can not hear the isolated tones. We're presumably talking about intermodulation that create harmonics in the audible range.
Also, Morten Lindberg of 2L says he needs extended frequency response above 22 kHz to record a proper impulse response without ringing.
So while we can not hear above 20 kHz, a wide frequency response is still useful.