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  #131  
Old 06-21-2003, 05:27 PM
B-Grade B-Grade is offline
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Default Re: Digi 001 discontinued?!

On the nyquist thingie...

frequencies of 8K may be reproduced with that scenario, but not accurately. Square waves sound different than sine waves.

Now, to speak against myself somewhat, to the human ear square waves become sinudial at around 15K. (IOW, square waves sound identical to sine waves after that frequncy).

However, by themselves, theoretically the human brain cannot discern volume increments less than 3 db. 3 db! I can attest to mixing bands and making adjustments of instruments in .5 db and hearing a difference. Why is this? The complexity of music trancends simple physics theories.

You are right that the ear cannot hear much above 20K. The ear has somewhat of a binary system of identifying frequencies. Unrolling the cochlea it forms a tubs. High frequencies are registered by hairs at the front, and lower ones on back. (BTW this is why we loose highs first, they are the first line of defense when the music is loud the hairs get ripped out there first. There is no rogaine).

However there has been a great deal of research on neural phisiolgy lately that is suggesting our senses may be better than their design. Yeah, they don't have a clue why either, but they can prove it in testing subjects.

Call Moulder out of retirement, he'll get to the bottom of it.

My wife is in the imaging world and they have been using mr. Nyquist's theories as well. That's how they have determined line frequencies and such. Now however...

They are capturing color much past the range of human sight. Why? So they can further manipulate the image. This is their bit depth. Very analagous to our bit depth.

Net up Sample frequency. Again, they are going higher. However, the printing process is also changing. High end mags like national geographic, where image detail and color rule, they have switched to stochastic screening, which is an intelligent dither.

How did they come up with this? The randomization of film is easily dismissed by the eye becuase of its changing nature. Fixed frequencies, although technically not detectable, are seen. BTW this random pattern is part of the love that we get from tape. The specs on tape defey everything. 90db? Should be worthless compared to 16 bit.

I'm wondering why nobody's freaked on SACD yet?
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  #132  
Old 06-21-2003, 07:54 PM
clorox clorox is offline
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Default Re: Digi 001 discontinued?!

Exactly. No one's claiming anyone can hear 40kHz.

BUT:
1) You may hear multiple 40kHz waves interacting and producing audible, subtle results.
2) Processing at these higher sample rates (96k and up) may achieve two things: the ability to "do math" on the data w/o losing data, and the ability to let (or add in) subtle, ultrahigh frequencies to interact with each other and the audible spectrum and possibly produce what some have described as "air", "warmth", or "that certain I-don't-know-what."

And we should not forget that we "hear" frequencies above 20k all the time as their chaotic interactions produce audible results.

But, being a programmer, I also love the mathematical point. Keep all the info till the last step! [img]images/icons/smile.gif[/img]
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  #133  
Old 06-21-2003, 08:03 PM
B-Grade B-Grade is offline
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Default Re: Digi 001 discontinued?!

Keep all the info until the last step indeed. That is one of the nice things about the DMX-R100 is the 56 Bit summing bus. Pile it all on, paint the whole picture, then reduce for size.

Graphics guys do this all the time for photo-comp ever since a program called live picture came out. Turned the whole industry on its ear. Whoops, eye, whatever.

And, for the topic, 001 we hardly knew ye.
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  #134  
Old 06-21-2003, 10:32 PM
clorox clorox is offline
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Default Re: Digi 001 discontinued?!

found a WONDERFUL article at digitalprosound.com which reinforces a lot of what we've been saying here re: high frequencies. They basically touch on everything we've talked about here, including the best explanation of Nyquist I've seen. Even I can understand it. [img]images/icons/wink.gif[/img]

I think it's important to stress, YET AGAIN, that most everything everyone has said on this board has been correct even if they APPEAR to be contradictory.

http://www.digitalprosound.com/Htm/S...ap2_Apogee.htm

Once of many nice excerpts:

"Why Record Ultrasonics?
As is widely recognized, most of us can ’t hear much above 18 kHz, but that does not mean that there isn’t anything up there that we need to record – and here's another reason for higher sampling rates. Plenty of acoustic instruments produce usable output up to around the 30 kHz mark – something that would be picked up in some form by a decent 30 in/s half-inch analog recording. A string section, for example, could well produce some significant ultrasonic energy.

Arguably, the ultrasonic content of all those instruments blends together to produce audible beat frequencies which contribute to the overall timbre of the sound. If you record your string section at a distance with a stereo pair, for example, all those interactions will have taken place in the air before your microphones ever capture the sound.You can record such a signal with 44.1 kHz sampling and never worry about losing anything –as long as your filters are of good quality and you have enough bits.

If, however, you recorded a string section with a couple of 48-track digital machines, mic on each instrument feeding its own track so that you can mix it all later, your close-mic technique does not pick up any interactions.The only time they can happen is when you mix – by which time the ultrasonic stuff has all been knocked off by your 48 kHz multitrack recorders, so that will never happen. It would thus seem that high sampling rates allow the flexibility of using different mic techniques with better results."
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  #135  
Old 06-21-2003, 10:48 PM
clorox clorox is offline
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Default Re: Digi 001 discontinued?!

And yet more research. Apparently, 44.1kHz is just not good enough for true stereo imaging of transient sounds. This is something I'm encountering a lot in my research, and here's one of the many quotes on this subject:

http://homerecording.about.com/libra...y/aa060998.htm

"How we determine the location of sustained sound is by the difference in volume between our ears. However for transient peaks, (sounds with a fast attack and release) we use delay to give us the cues necessary to place sounds in the stereo field. The difference between two sources of sound is called "just noticeable difference" and it is around 5-7 microseconds. When the timing of sounds around us are presented to our ears, we can exactly place where their source is based on this minute timing difference. Our ears are quite the intstruments!

The problem with our current sampling rate of 44.1k is that the timing difference between samples is 20-28 microseconds. This is not nearly enough to represent how we hear things in the real world. In this case, analog is superior. However with a higher sampling rate we could reproduce sound much more accurately. A sampling rate double our current standard would go a long way in fixing the above mentioned problem. Indeed if it was 4x our current rate it would certainly do the job as well as analog."
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  #136  
Old 06-21-2003, 10:58 PM
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Park Seward Park Seward is offline
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Default Re: Digi 001 discontinued?!

Quote:
Originally posted by guitates:

Park--It is Not the equipment...It is the TAPE...

A trumpet sounds like a trumpet because of it's unique harmonic overtones...etc...

You start with fundamental tones, and the overtones are produced above the fundamental, at the Octave--the 12th, the 2 octave and up to multiple overtones.

I am saying (not my opinion, but many Audio Student Profesionals have suggested that) your Frequencies rising up from any fundamental, are Restricted by your sample rate in the Digital Domain, and un-restricted (rising upwards to 200,000 in rare cases) by analog TAPE.
<font size="2" face="Verdana, Arial">Just to make it clear, are you suggesting that analog tape can record 200k audio frequencies? I have an Ampex 440B-2. It isn't close to 200k, not even 100k. I can tweek it flat to 20k but it falls off fast after that.

Take a recording of a trumpet and cut off all frequencies above 5k. Cut off all the "unique harmonic overtones". It still sounds like a trumpet. What does that do to your theory of "über harmonics"?
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  #137  
Old 06-21-2003, 11:17 PM
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Park Seward Park Seward is offline
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Default Re: Digi 001 discontinued?!

Quote:
Originally posted by clorox:

I think it's important to stress, YET AGAIN, that most everything everyone has said on this board has been correct even if they APPEAR to be contradictory.

If you record your string section at a distance with a stereo pair, for example, all those interactions will have taken place in the air before your microphones ever capture the sound.You can record such a signal with 44.1 kHz sampling and never worry about losing anything –as long as your filters are of good quality and you have enough bits.
<font size="2" face="Verdana, Arial">Yes, recording a string section or a trumpet quad live will sound better than recording individual instruments and then mixing them together. But it has nothoing to do with ultrasonic harmonics. It has to do with each instrument playing a slightly different note with slightly different tones. Then aucoustic interaction and the interplay of the intermodulation on the mic diaphram (or ear) cause the sound. By having different transducers receiving different sounds at different locations and times will not produce the same effect (as with different mic setups).

Listen to two singers harmonize on two mics or on one mic. It sounds better if they sing on one mic. I don't think anyone will suggest that the voice has useful harmonics much above 10k.

And to the first point... some do indeed have very wrong ideas. They are really incorrect and do a disservice to those trying to learn.
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  #138  
Old 06-21-2003, 11:26 PM
Chaasm71 Chaasm71 is offline
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Default Re: Digi 001 discontinued?!

Hey B-Grade, you mentioned that your wife is into imaging stuff. You also mentioned stochasitic screening. My ears went straight up! I work at a company called Creo (your wife may well have heard of us). We make high end digital imaging systems which image stochastic screening. I wouldn't really call stochastic screening dithering per se, since we aren't reducing bit depth with it, but rather I would say it is a frequency modulation approach to generating grey scales (vs. traditional screening which employs amplitude modulation at a fixed frequency). It's pretty cool technology, and lets printed work look really photographic. So, if we can make digital print look analog, let's hope we can get digital audio there! [img]images/icons/wink.gif[/img]

Cheers!

Charlie.
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  #139  
Old 06-22-2003, 12:45 AM
clorox clorox is offline
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Default Re: Digi 001 discontinued?!

Quote:
Originally posted by Park Seward:
Yes, recording a string section or a trumpet quad live will sound better than recording individual instruments and then mixing them together. But it has nothoing to do with ultrasonic harmonics. It has to do with each instrument playing a slightly different note with slightly different tones. Then aucoustic interaction and the interplay of the intermodulation on the mic diaphram (or ear) cause the sound. By having different transducers receiving different sounds at different locations and times will not produce the same effect (as with different mic setups).
<font size="2" face="Verdana, Arial">It is a scientific fact that these instruments produce frequencies above human hearing. The trumpet with a mute shows significant energy up to 100 kHz before dropping into the noise floor. It is a scientific fact that we can hear and measure "beats" formed by the interaction of these ultrasonics. These are facts, not opinions, and the results have been documented in labs using a spectrum analyzer. Not up to debate.

Hop on Google. It took me thirty seconds to find this paper:
http://www.tannoyna.com/professional...p_wideband.pdf

How much it contributes to pleasantness of the overall sound is subjective, which means neither you nor I can say anything about that with authority.
Quote:

Listen to two singers harmonize on two mics or on one mic. It sounds better if they sing on one mic. I don't think anyone will suggest that the voice has useful harmonics much above 10k.
<font size="2" face="Verdana, Arial">
Alright. Why don't you put a 10k low pass filter on all your vocals? Because it would sound horrible, that's why. Sibilance in human speech has been shown to have energy above 40kHz.
Quote:

And to the first point... some do indeed have very wrong ideas. They are really incorrect and do a disservice to those trying to learn.
<font size="2" face="Verdana, Arial">I agree. But anyone who thinks that ultrasonic frequencies can't or don't combine to form audible sonic frequencies is one of these "wrong" people. Anyone who thinks we can't detect a stereo difference between two signals by as little as 5-7 micro seconds is "wrong". Anyone who thinks that common musical instruments don't produce A LOT of ultrasonic energy is wrong. Scientifically, absolutely, look-it-up-in-your-EE-321-Signals-Class-textbook wrong.

By the way, speaking of misleading, there are some EXTREMELY misleading charts in textbooks and on the web which show the frequency range of many instruments. Remember that these charts show FUNDAMENTALS ONLY. The trumpet, for example, produces frequencies from 200Hz to above 100kHz. Playing an A on your guitar will be producing a sound wave at 440Hz, but there are also many higher harmonic tones which may be out of the range of your hearing! Without these harmonics, that note would sound like a 440 Hz sin wave. And do not believe for a second that you're not producing a little 40kHz when you're talking to your mom on the phone. [img]images/icons/tongue.gif[/img]

Also, if anyone would care to take things out the realm of OPINION and into the realm of SCIENCE, please post links to your evidence. If you want to try to convince everyone that the world is flat, at least have the courtesy to post a link to a map.
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  #140  
Old 06-22-2003, 12:49 AM
clorox clorox is offline
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Default Re: Digi 001 discontinued?!

Quote:
Originally posted by Park Seward:

Take a recording of a trumpet and cut off all frequencies above 5k. Cut off all the "unique harmonic overtones". It still sounds like a trumpet.
<font size="2" face="Verdana, Arial">Yep. A really, really lousy trumpet.

[img]images/icons/rolleyes.gif[/img]
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