What you can hear, versus what you can hear
Jul 10, 2001 at 8:58 PM Post #2 of 18
Interesting.

I wonder if it's possible that upper harmonics beyond the 20khz level, interact with sympathetic lower freqencies and somehow affect the way we hear them?

If so, cutting off at 20khz, even if we can't specifically hear these frequencies on their own, may still be detrimental to realisitic sound reproduction. After all, if these frequencies are indeed there in real life, there's a possibility they do somehow affect what we ultimately hear.

Then again, there are light spectrums we can't see and all sorts of radiation/microwaves flowing through us that we can't perceive. Do these make a difference in our sensory perception somehow as well? Beats me.
 
Jul 11, 2001 at 12:57 AM Post #3 of 18
If super-20kHz sound effects the bone-conduction of additional vibrations, then it certainly has an effect on our hearing. Isn't the reason we hear our own voice differently than others because we hear the sounds made by our vocal chords through our bones as well as our ears?

Of course 40-kHz sound probably has a smaller effect on human hearing than sub-20-Hz sound, but if there is any effect, I believe that its reproduction is in the future, just like recording formats of even higher resolution than SACD and DVD-A!
 
Jul 11, 2001 at 4:35 AM Post #4 of 18
I know, but of all the variables controlling the difference between live music and recorded... this is probably the weakest factor.

I don't know what it's gonna take, electrostatic panels 40' tall and megawatts of power, etc.. but it would be interesting to find out that the difference between hearing a wood block hit recorded vs live was some 20kHz+ harmonics we don't know we hear...
 
Jul 11, 2001 at 6:28 AM Post #5 of 18
You know, if a brain scan shows difference with and without ultrasonics, that's all the proof I need.

Besides, it's moot since new formats have already arrived... And it's not like there are any technical difficulties in recording and storing all that extra data.
 
Jul 12, 2001 at 12:42 PM Post #6 of 18
mbriant: I think that if there is an abrupt cutoff at 20kHz, it does affect the frequencies below that. If you've ever played around with a graphic equalizer, when you pull down 22kHz the sound does change. It's like all of a sudden you remove a very tiny bit of all instruments that spread up into that range and the overall effect is noticeable. Whoever decided to settle for Red Book standard for digital CD blew it badly.
 
Jul 12, 2001 at 8:50 PM Post #7 of 18
Technically we don't even percieve sound properly. According to my musician friend sound engineers and scientists are basing their measurements of sound on a system that presents sound in a false manner. Mostly because sound technically is not a waveform. A waveform is just a method of viewing sound energy. It is better to see sound as a spheres within spheres type of model. Also, we often see sound as beaming from one point to another. However sound radiates in all directions. Most current speaker designs attempt to project sound and focus it at a point, this is wrong and wholly unnatural.
According to him we still don't "know" what sound is. I tend to agree with this. It isn't a wave, yet it "can" be percieved as a wave although this is fundamentaly wrong. Sound is actually a pulse, it is not connected by troughs and peaks on a waveform. Each pulse is independent of the next, the energy only appears as a wave as it distorts the material through which it is passing. Sound does not stream, it pulses. I am sure people realize this however we think a better method of illustrating sound other than the waveform should be devised.
Also the idea that there is no sound in space is both right and wrong. Technically no there is no sound in space we can hear. Scientists however now believe that the dark spaces between planets for which we have little explanation are actually some kind of matter. They called it oh so fittingly "Dark Matter". Waves of energy can pass through Dark Matter the same way they do air or water so their must be the potential for sound energy. It can be realized then that sound energy is purely motion of molecules. We often see sound as a creation, however it is everywhere and constant. This is possibly a reason for the limitations on our frequency range of hearing. To hear more might incur madness.
Considering these things its his and my own feeling that we just have the totally wrong perception of what sound is. And that our whole method of approaching it needs to be revised.
 
Jul 12, 2001 at 10:13 PM Post #8 of 18
This may very well be true.... providing your "musician friend" has somehow discovered something that "scientists and sound engineers" don't know about.

It's true that sound waves ( or whatever they are) do radiate in all directions, but it seems that a sound coming from a fixed source....like a loudspeaker or a mouth or whatever.... is focussed primarily outward, away from the speaker or mouth. Wherever the air is being pushed.

When someone is speaking, someone standing in front of them will hear what they are saying louder than someone behind them. I'm not sure if the sound that reaches the person behind them is somehow coming out of the person's mouth and then radiating backward, or if they are hearing reflections bouncing around.
 
Jul 12, 2001 at 10:55 PM Post #9 of 18
mbriant - i think its a combination of both (whether they are hearing reflections or radiating backwards..)
 
Jul 17, 2001 at 12:37 PM Post #10 of 18
Similar studies were conducted just prior to the CD format to question weather the 18.5 KHz. of the Then Perposed CD format would limit musical Enjoyment. All came to Different Conclusions with ones by Phillips and Sony showing that No life Exsists above 18KHz. Musical lovers and the NBS Showed great corolation between the upper octave Extention and Musical satisfaction, But since all your CD's are By design Choped off Your ears will never hear those Upper harmonics mentioned in the Artical mr Apheared refered to. So if Ya want above 20 KHz. Go with Old fashion LP's A good MM Picup can go to 50,000Hz. Easy and some MC types up to 200,000Hz. so why wait for some New format in the future that may go a few KHz. more. Just use your Lp records Now.
 
Jul 17, 2001 at 5:19 PM Post #11 of 18
If you do listening test yourself:
If you use a single driver to playback both < 22 kHz and >22 kHz there will be additional IM products in the range below 22 kHz which can be perceived as a change. IM products are faults produced by the driver and have nothing to do with perciving frequencies above 22 kHz.
Any listening test which has proven differences between 44.2 kHz and 96 kHz needs to be checked for this.


ppl, as far as i know LPs are limited somewhere around 16 kHz to reduce the strain on the cutting needle (what is the right expression for it?).
If the things about the LP format on http://www.elpj.com/why.html are right no needle can read any information beyond 30 kHz.


Why is anyone that worried about not beeing able to hear over 22 kHz? I mean, if we can't hear anything beyond 22 kHz it only reduces the technical requirements for music playback, not the musical satisfaction.
 
Jul 18, 2001 at 7:40 AM Post #13 of 18
Boy am i the only one hear that remembers records and more inportently Quaddraphonic records, Most notably recorded using RCA's CD4 Format. Well allow me to refresh: The CD4 encoded the Rear channels into a sub carriiour at about 50KHZ. Relitivily Cheep cartrages would reproduce this tone so the PLL used in the DC4 System could decode the addional two rear channels. This is similar to the Technology used in FM Stereo Except the FM subcarriour is 19 & 38 KHz. Due to the Limited bandwidth of the Alloted FM Channel.

Resources on this issue are in every Audio mag testing the CD4 Compatible Pickups. in addition my own testing using a CD4 test record reveiled that responce is at least up to 80KHz. on the Sure M95ED, V15 type IV, 50KHz on the Sure V15 type II I had mt Audio technica AT155LC measured and it went to 100KHz.

So go back through the old Back issues of Stereo review, high fidelity and other rags and criticaly review Pic-up data.

The Limit of the Needle is 16 Hz. not 16KHz. this is why records are Cut with an RIAA curve that cuts the Bass and boosts the treble and the Phono preamp has an Inverce RIAA curve to cut the treble and Boost the bass. this was done to keep grove spacing tight so as to get more Listening time, and to allow most Low complience cartradges to track them. The 16 Hz. limit is dependent upon tonearm and Picup mass in concert with the Complience of the Needle gives a spicific resonent frequency. 8-16 HZ is about the range with most pic-ups. so if you cant find this data post back i will dig out my old stereo reviews
 
Jul 18, 2001 at 1:10 PM Post #14 of 18
Jul 18, 2001 at 3:03 PM Post #15 of 18
Yes i am sure. moreover your own statement explaines that the Rear channels are 20-40KHz. Now This is a Multiplexed signal just like FM-Stereo is, So the Phase and Distortion must be low in order to alow the Phase locked Loop to properly Decode the rear channel info. Continue your research and you can find out more on this.
 
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