What's the use of a 192 kHz sample rate?
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From: Piergiorgio Sartor on 4 May 2008 11:20 Jerry Avins wrote: > I recently had my hearing tested, both through the ear canals and via > bone conduction. The results match to within a few dB, indicating that > my loss of cochlear or nerve, rather than associated with eardrum or > ossicles. I don't think the alternate paths account for much in general. Uhm, but the alternate paths, usually, are no so specific as per hearing test. There are several issues here. One is to distinguish, and it is not easy, between what we can hear and what "sounds good". The two things may not be equivalent. There is a difference between: 1) Attending live a Wagner's concert, in which, for the record, the orchestra needs some added instruments. 2) Listening the same concert in front of loudspeakers, which can "only" reproduce up to 20KHz. 3) Having some headphones beaming a pure tone directly into the head, with someone asking to press a button when something is heard. The first is like bathing in a ocean of sound. The second is like swimming in a pool of sound. The third is like measuring the water's temperature. And we, here, are discussing how warm or cold humans can feel the water. The problem is how nice or not is the water... bye, -- piergiorgio
From: DigitalSignal on 4 May 2008 12:18 Hi rickman, can you refer the company who can produce or analyze the signals with 140 dB SNR? I have never seen one. I guess they are not using any digital technology, or they are look at very low frequency signals. Right? James www.go-ci.com
From: emeb on 4 May 2008 12:19 On May 3, 9:25 am, Steve Underwood <ste...(a)dis.org> wrote: > For people who say supersonic sound can't play a part in a listening > experience, trying being in a room with a high intensity of supersonic > energy. Under some conditions (I'm not clear which) you can sense it, > even though you can't hear it. It actually feels like something loud > that you can't hear is going on. Its a very odd feeling. I've noticed this too. Some relatives of mine have an ultrasonic dog deterrent which looks like a TV remote. Pushing the button on that thing produces a sensation of intense pressure, even though I can't hear above about 13kHz. My guess about what's happening is this: Even though my cochlea isn't responding to the high frequency, the mechanical linkage of the inner ear is still transmitting that ultrasonic energy. Perhaps there are other 'side channel' senses involved - aren't there muscles on the tympanum that provide a sort of AGC function? Maybe the control loop that drives them has a wider sensing bandwidth than the nerves that transmit frequency information to the brain. Eric
From: rickman on 4 May 2008 22:54 On May 4, 3:40 pm, nos...(a)nospam.com (Don Pearce) wrote: > On Sun, 4 May 2008 12:28:34 -0700 (PDT), rickman <gnu...(a)gmail.com> > wrote: > > > > >On May 4, 12:18 pm, DigitalSignal <digitalsignal...(a)yahoo.com> wrote: > >> Hi rickman, can you refer the company who can produce or analyze the > >> signals with 140 dB SNR? I have never seen one. I guess they are not > >> using any digital technology, or they are look at very low frequency > >> signals. Right? > > >> Jameswww.go-ci.com > > >Thales Communications, makers of military radios. This figure came up > >in the context of digital interference with the RF sections. I was > >told that the digital noise had to be below -140 dB to prevent > >desensitization of the receiver. These units are *very* overbuilt and > >far surpass anything commercial I have seen. One spur anywhere in a > >huge range, 30 MHz to 500 MHz, IIRC and they are back to the testing > >room to add more copper tape or to put more resistors in clock lines, > >etc. > > A desensitization level is going to be measured in dBm, and -140 is a > very ordinary figure. If external noise interference is present at the > input of a receiver, it will add to the inherent noise already there, > raising it. This is called desensitization. A common interference > requirement is that a desensitization of no more than 1dB is > permitted. > > The -140 in this instance is just a receiver input level, and nothing > to do with S/N ratios, dynamic ranges or anything like that. > > I would be very surprised if anything military surpassed the spec of a > commercial design. Far too few units are built to justify the number > of trips round the design cycle that are needed to remove every spur > from and maximise performance. That fact that they have to bodge units > with copper tape to make them work rather bears this out. > > Certainly when I was designing low noise converters for domestic > satellite systems I achieved a guaranteed total noise figure 0f 0.25dB > at 12GHz, and the entire unit had a works cost price of 11 dollars. > Nothing military has ever come close to that kind of performance or > price. I am not an RF guy and the figure I actually remember was 150 dB. I hedged it a bit as 150 sounded rather extreme to me. I dunno if 150 is anything outside of ordinary or not. When you say that it costs too much to go around the design cycle many times, you clearly don't know much about the military procurement process. On the last radio that they built while I was there, they were up to rev 14 of the board that had nothing but the UI controller and external interfaces. You need to remember that often the development process is cost plus and the customer is *asking* for tough specs. It is only when they can't be delivered that they back off. What is really funny is that you are getting wrapped around the axle about my use of this figure when that was really just an aside to an aside of my original point. Funny how these discussions get so far off topic. Did you read my post which used the original 140 dB figure?
From: rickman on 4 May 2008 15:28
On May 4, 12:18 pm, DigitalSignal <digitalsignal...(a)yahoo.com> wrote: > Hi rickman, can you refer the company who can produce or analyze the > signals with 140 dB SNR? I have never seen one. I guess they are not > using any digital technology, or they are look at very low frequency > signals. Right? > > Jameswww.go-ci.com Thales Communications, makers of military radios. This figure came up in the context of digital interference with the RF sections. I was told that the digital noise had to be below -140 dB to prevent desensitization of the receiver. These units are *very* overbuilt and far surpass anything commercial I have seen. One spur anywhere in a huge range, 30 MHz to 500 MHz, IIRC and they are back to the testing room to add more copper tape or to put more resistors in clock lines, etc. |