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Re: Let's compare numbers and see why mine are different from yours

sm: ""
I don't see how you drew that conclusion.""

I will explain..

sm: ""
A sound with a period of 5 uSec has a frequency of 200 khz and a sound with a rise time of 5 uSec has a frequency of 50 khz. Both of these are far beyond the range of human hearing and far beyond what exists on all but the very rarest of recordings specially made to contain them.""

It is actually worse. Test subjects have demonstrated (statistically valid tests, of course..) the ability to learn to discern at the 1.5 uSec level, which from your calc method would be 666 Khz. Clearly, ludicrous frequencies, and I have no intent on stating audibility over 20K. We do indeed react at ultrasonic frequencies, as I have found this from experience at 25K, but that is not the issue we speak of here.

Examine your calc assumption..you assume a peak to peak time for the frequency, that is not what localization in time is about. In time, it is about the delay from ear to ear.

Back when I had to avoid the raptors (yah, waaaay back), if one wanted to buy a scope probe, one had to look at the response time of the probe. A typical probe I purchased had a 1.7 nSec settling time (arbitrary settling percentage, of course), and that determined the bandwidth of the test system.

For audio, we are of course only capable of frequency bandwidth of 20 K give or take, but yet, we are able to localize with a time difference equivalent to 10 times our system bandwidth. That initial understanding slapped me upside the head, it's just outright counter-intuitive.

Should we look at this "system" with a 20K bandwidth test instrument? If I use a pair of scope probes which are band limited to 20K, can I even see a 5 uSec interchannel difference??

I do not consider testing a system's response using equipment a factor of ten slower than the desired parameter. In fact, I would expect the gear to be ten times better (as a minimum) than the required resolution.

For localization, I'd use a test system with 100 nSec resolution to look for 1.5 uSec entities. That's why my test load is 60 picohenries inductive and 4 ohms, there is no question as to reactance within the required parameter.

Cheers, John


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