Regards flipping see here Amplitude Modulation AM Index & Depth >> Electronics Notes
Regards envelope attack equating to modulation, yet to be convinced 😉
Regards envelope attack equating to modulation, yet to be convinced 😉
JN,
In poking around trying to make heads or tails of what’s being discussed here I came across this patent for digital hearing aids, it seems to hit on a lot of what your talking about and how it might pertain to hearing.
US6173062B1 - Frequency transpositional hearing aid with digital and single sideband modulation
- Google Patents
If it’s irrelevant please disregard.
In poking around trying to make heads or tails of what’s being discussed here I came across this patent for digital hearing aids, it seems to hit on a lot of what your talking about and how it might pertain to hearing.
US6173062B1 - Frequency transpositional hearing aid with digital and single sideband modulation
- Google Patents
If it’s irrelevant please disregard.
Regards Mark mentioning hearing over 20KHz, when I was much younger I was repairing a colleages 400Watt amplifier, we had no speakers to hand and the noise would have given things away, so we ran it into two high power rf loads in parallel. The actual amplifier whilstled at the notes passed through it from a signal generator. That lead to a game where we asked someone else to rotate the signal generator dial while we listened one at a time. I repeatedly stopped at 22kHz, one of the other younger guys stopped at just a bit higher and some of the others were at 19Khz or so. If it was not repeatable we knew the other person was guessing!
So when younger some but not all can clearly hear above 20k. Dont forget that a lot of the measurements we rely upon for deciding these limits were measured on large groups that had done significant Military service that will have done their ears no favours.
The thing is, if they are created due to the attack envelope, they will be everywhere not only at high frequencies. The fact of the matter now is, as far as I'm concerned, jn has to provide some actual proof .......... I hear a song coming on.................I may be some time.
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Exactly. The trig identity modulation is comparable to 200% modulation. Once I realized the different definitions, it was easily clear why the trig identity suppresses the carrier in an FFT
Note that I posted two pics I pulled from MRI sites. They show how an exponential decaying envelope spreads the spectrum sidebands. The faster the decay, the more the spread.
The only way I am aware of to find the sidebands in that example is using Scott's technique of subtracting input from output of a brickwall, the Gibbs envelope will show the sideband energy being removed.
A perfectly reasonable thing.
20k or 2.5k it is only 17.5k and 22.5k remove the 22.5k and you have 17.5k there is no frequency translation.
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There is no carrier, as people keep trying to explain. Scott Wurcer already told you the waveform you have is double-sideband suppressed-carrier.
You see, or don't see, when AM radio is modulated digitally the carrier has to be added back in with the sidebands. Otherwise, the carrier gone after perfect multiplication is used for sideband creation. That's why you see the 1 circled in red in the equations attached below.
The reason old radio transmitter designs didn't have to do that and had to filter out baseband audio instead was because they didn't have perfect analog mulitipliers, so they used non-excessive intermodulation (distortion, actually) to get the job done.
Again, what you see is an interference pattern, not the same thing as a third frequency at all (when talking about frequencies, filters, and sampling).
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Of course. Who said anything different?
Of course, that is only in an FFT. If you look in the time domain, it is all 20k in the envelopes. Just look at the overlap plot I put up.
The fact that an FFT doesn't see the 20k is because the phase of the 20 k flips 180 degrees every envelope.
And, remove the 22.5, and only 17.5 is left.
I am confident you cannot do a good FFT on only one lobe, right? You could pull every other lobe if you wanted to detect the 20 k.
Jn
You are not tracking the discussion, I assume it is accidental.
AM straight modulation retains the carrier. As per PMA's posts show.
Cosine multiplication modulation retains the carrier as well, but inverts phase every lobe. 200% modulation, which are not good for broadcast. But is exactly what adding sines does.
And again, you are diverting from the crux of the discussion.. Envelope modulation will cause sidebands.
I am worried about such sidebands crossing the filter threshold with music, particularly cymbals and such.
Jn
Have no fear. Shannon and Nyquist are not broken. Those guys had more IQ than the entire arguing thread on here. Nothing being yacked about here is going to change it.
Speaking of cymbals, play some Rush tonight in memory of Neil, we are reminded that life is short.
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