Ron,
All tones generate subharmonics as well, which in the case of 40kHz, would be back in the audible range.
Lee
All tones generate subharmonics as well, which in the case of 40kHz, would be back in the audible range.
Lee
Now I will reask Marty this question: how do we know that? How do we connect those 2 sentences? Where is the proof of audibility?Ethan's key argument that jitter, if it is 100dB below the signal, must by definition be inaudible, reminds me of the old argument that an amplifier's performance at 40KHz must be irrelevant since we can only hear up to ~20KHz. We now know that not to be the case as the harmonics of signals at 40KHz may be heard in the audible range. The main reason I think jitter is likely audible is the recent work of some vehement anti-jitterholics such as Ed Meitner, whose recent effort , the XDS1, greatly impressed me.
A question: Are the subharmonics generated in the ear? It takes a nonlinearity to generate subharmonic (mixing) products, and I am curious if the ear (or ear/brain system) does this. I do not know.
Curious - Don
There is also a bit more information here: http://en.wikipedia.org/wiki/Ultrasonic_hearing
I'm 100 [ or should I say 120? ;-) ] percent in agreement with you on number 1. Actually, I like your number 2 as well.Personally, I like to go 20% or so above 20Khz for two reasons:
1. There is some evidence of people hearing above 20 Khz and the modulation effects thereof. See below.
2. It gets rid of a lot of arguments that way ."[/i]
There's still no definitive answer to whether frequencies about 20kHz are needed. However, this study shows that with a crash cymbal, 40% of the total sound energy is above 20kHz.
http://www.its.caltech.edu/~boyk/spectra/spectra.htm
I've tried some experiments with recording jangling keys (68% of energy above 20kHz), sampling at 96kHz and I can always tell if I put in a filter at 30kHz. However, that may be because of my badly implemented filter, or my lousy recording technique.
The other aspect of the Boyk study that I find really interesting (more so for me anyway) is that it shows how incredibly complex the fundamental/harmonics are even for a single note (B flat in this case).
In the 1st chart for trumpet; up to 8khz it could be said the harmonics are peaking around 48db, at 30-32khz is peaking just above 26db to around 30db, while around the 20khz is peaking just above 30db.
In a way seeing how complex the waveform is for a single note makes me wonder just how comparable single tones are for testing audio hardware.
I smell a bait coming.Amirm, would you agree re: jitter --
I think some in the thread doubt it. But I take a win when I can .1. certainly it CAN be audible (which I hope nobody doubted anyway),
yes although it is better to say anything but random jitter is more audible.2. more likely to be audible if correlated to signal ('deterministic' -- this too was already known, and the spectrum matters too)
I have never attempted to test it with speakers. So I have no data to share there.3. more likely to be heard over headphones, using a revealing probe signal (also a no-brainer)
BUT
4. QUITE UNLIKELY to be the culprit, with *music* played over *loudspeakers*, i.e, the sort of situation typical when jitter is blamed for bad sound by 'high end/audiophile' listeners
...Thanks to Steve McCormack, I have a recording of every key of a grand piano. He made a recording where he tried to hit every single key with the same amount of strength and recorded it. Playing this through any system is usually a revelation - how some notes boom or are recessed show up incredibly well the system/room interaction...
I'll ask him if I can release it to this forum - and I should be probably be able to attach it as a WAV?
Not sure if a thread on jitter is an appropriate place to put it though.... Mods?
Perhaps you can put the file in your PNWAS Forum