Yes , I had that over sensitivity too. My 29 inch Sony had it . I went so far as to put silicone on the CRT coil AND but the whole tv in a wooden box ( with fans.)
It was around that time my tinnitus started too.
Not hearing, but damage due to cavitation, High levels of ultrasonics are hazardous
https://pmc.ncbi.nlm.nih.gov/articles/PMC8954895/
A frequency difference measured in Hz, so it is a frequency. This is the basis of IMD, superheterodyning, and tuning.
If I give you 273 oranges and you give me back 271, what you have left is two. Oranges.
Is the IF -intermediate frequency - produced by superheterodyning not a frequency? This is absurd.
Thus is a rather basic fourth form point to be debating here.
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When two frequencies 'intermodulate' a third frequency is generated > once called a "Beat Frequency".
^^^ Incorrect.
It looks like there is a lot of confusion about beat frequencies and intermodulation in this thread. Its not the first time its happened in some thread and probably won't be the last.
I will try to take a stab at explaining.
A beat note is not a frequency in the strict sense of the Fourier transform. However, a beat note is something that may be perceived as a frequency by the human perceptual system.
Beat notes are volume modulation envelopes (or we could say they are interference patterns) produced when two frequencies are added. Adding is a linear operation, but only nonlinear operations can produce new frequencies, so no new frequency can be produced by adding. To see that, its easy to add two frequencies in the digital domain in a DAW. If an FFT is taken of the resulting output waveform, there will only be the two original frequencies. If we want to see the beat note in a mathematical analysis, we would have to use the Hilbert Transform to find the volume envelope waveform.
Intermodulation is something else entirely. We can intermodulate two frequencies by multiplying them together. The result is that two new frequencies are created (since multiplication in this context is a nonlinear operation). The two new frequencies are called "sidebands."
Thus, sidebands and beat notes are two entirely different things which are produced by entirely different processes. A beat note is not a true frequency in the strict sense of the Fourier transform.
It looks like there is a lot of confusion about beat frequencies and intermodulation in this thread. Its not the first time its happened in some thread and probably won't be the last.
I will try to take a stab at explaining.
A beat note is not a frequency in the strict sense of the Fourier transform. However, a beat note is something that may be perceived as a frequency by the human perceptual system.
Beat notes are volume modulation envelopes (or we could say they are interference patterns) produced when two frequencies are added. Adding is a linear operation, but only nonlinear operations can produce new frequencies, so no new frequency can be produced by adding. To see that, its easy to add two frequencies in the digital domain in a DAW. If an FFT is taken of the resulting output waveform, there will only be the two original frequencies. If we want to see the beat note in a mathematical analysis, we would have to use the Hilbert Transform to find the volume envelope waveform.
Intermodulation is something else entirely. We can intermodulate two frequencies by multiplying them together. The result is that two new frequencies are created (since multiplication in this context is a nonlinear operation). The two new frequencies are called "sidebands."
Thus, sidebands and beat notes are two entirely different things which are produced by entirely different processes. A beat note is not a true frequency in the strict sense of the Fourier transform.
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Humans wouldn’t hear the beat note if intermodulation wasn’t occurring SOMEWHERE. Yes, it happens in the ear/brain - and to a far greater extent than in a quality amplifier.
Humans can and do hear beat notes just fine without IMD in an amplifier. You can hear it in a piano that's out of tune. Or, a guitar.
How many here haven't ever tuned a guitar while listening for the beat notes between two strings?
https://en.wikipedia.org/wiki/Beat_(acoustics)
How many here haven't ever tuned a guitar while listening for the beat notes between two strings?
https://en.wikipedia.org/wiki/Beat_(acoustics)
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Some people can hear above 20kHz. That's just a fact. There is not a hard cut-off at 20kHz.
And the beat note is in your head - literally. The ear compresses amplitude, roughly logarithmically. Compression at the envelope rate causes IMD, and you HEAR that as an added tone.
Good amplifiers are CLEAN by comparison.
The human auditory system is highly nonlinear, non-time-invariant, and non-stationary. The fact remains that beats are amplitude fluxuations due to wave interference effects when frequencies are summed. The amplitude fluxuations do not result from an intermodulation process, and they are not new frequencies in the strict Fourier Transform sense. Subsequent nonlinear processing can then produce IMD (or other distortion) from, say, the two original true frequencies in the Fourier sense and or perhaps from the amplitude fluxuations, but its a separate, later process. That said, if the amplitude fluxuations were part of what produces some IMD in the auditory system, then there should be at least two beat notes heard simply because intermodulation produces sidbands (and not only a single beat note).
Can we agree on that much?
Can we agree on that much?
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https://www.google.com/search?q=ultrasonic+modulation+to+create+audio+signal&sca_esv=63f0b51ce1ca40c5&sxsrf=AHTn8zoblQ6D4zTIk65MpW0hcu5XV4WzZA:1741405650447&source=hp&ei=0r3LZ6brFuS00-kPycSCkAY&iflsig=ACkRmUkAAAAAZ8vL4vqkOYaRAWfNEmBMEJzHNo0qhEIG&oq=ultrasonic+modulation+to+create+audio&gs_lp=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&sclient=gws-wiz
https://en.wikipedia.org/wiki/Modulated_ultrasound#:~:text=Ultrasound can be modulated to,by a modulated-ultrasound receiver.
https://en.wikipedia.org/wiki/Sound_from_ultrasound
https://en.wikipedia.org/wiki/Modulated_ultrasound#:~:text=Ultrasound can be modulated to,by a modulated-ultrasound receiver.
https://en.wikipedia.org/wiki/Sound_from_ultrasound
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Intermodulation produces sums and differences of multiples of the contributing source frequencies. Simple 2nd order IMD in the ear of nearby fundamental frequencies can produce an audible difference tone as well as a sum tone. But the sum tone will be higher in frequency, possibly where sensitivity is lower, and if the toned were very close will just sound like an overtone of the initial tones. Wider spacing of the two tones, one low and one much higher will produce sidebands around the higher tone -- sum and difference frequencies.
While you do it, see to that you monitor the band with a mic + RTA to see if anything non harmonic is present - there are other crap sticking out their ugly faces as you try to reproduce 12k from speakers and amp etc that is not necessarily x2, x3 x4 fo... so that you dont hear the sparkling of a surround or the distortion/noise/oscillation of an amp when you output that 12k.
//
Id say thats often distortion of some sort... the replication effort of 20k excites all sort of other crap... and you think you hear it...
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Your "logic" is wrong.
I am at loss to understand how you don't know the basic thing about how the tuning is done. Tuning is done by listening two audio frequencies simultaneously - our ears can not hear the beat (i.e. frequency difference) without the two stimulus playing simultaneously! So, you can't hear 1 Hz, without hearing to two different frequencies simultaneously, for example 441 Hz and 440 Hz. Play single 1 Hz audio frequency (from some reeeally good subwoofer) and you will hear nothing, zero, zilch, nada,...
Your "analogy" is very, very wrong.
Let change the word "oranges" with the word "violins" in your "analogy":
If I give you 273 violins, all detuned differently from the perfect pitch of 440 Hz, and you gave me back 271 violins, what you left is two. Violins.
But what happened with the pitch/frequency difference between those two violins? Nothing. Wrong analogy.
Moral of the story: analogy must be logical.
You don't understand the basic science of the beat frequency.
Here is a good example:
https://en.wikipedia.org/wiki/File:WaveInterference.gif
Read carefully the Description below the gif animation.
Look how the two different frequencies make a beat "wave" - beat you are perceiving is not the frequency difference per se, but temporally changing amplitude of the interference product of those two frequencies.
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Dynavector in the 90's had an invention how to create deep low frequency illusion by tiny wideband speakers. It worked on the principle of superposition of two higher frequencies that were close enough. There was some secret psychoacoustic processor in front. I heard it, the result was convincing.