It is accepted that many people can detect ultrasonic frequencies at least up to 40KHz. This is why I add a serious ultra-tweeter for serious listening tests. Of course normal program material might not have much, except for distortion, but extended recordings sound better with extended response.
I have a short story about the problem with ultrasonic frequencies, and their detection. About 50 years ago, a popular hi fi store in the SF Bay area used to leave their ultrasonic transmitter (for burglar detection) on during the day, apparently because the salesmen could not detect it. I took a girlfriend to this store, and 1/2 hour later she complained about a headache. I could detect something was wrong myself, but it did not bother me that much. Just think about how much business they potentially lost leaving this ultrasonic transmitter on! By the way, they went out of business after a couple of years.
I have a short story about the problem with ultrasonic frequencies, and their detection. About 50 years ago, a popular hi fi store in the SF Bay area used to leave their ultrasonic transmitter (for burglar detection) on during the day, apparently because the salesmen could not detect it. I took a girlfriend to this store, and 1/2 hour later she complained about a headache. I could detect something was wrong myself, but it did not bother me that much. Just think about how much business they potentially lost leaving this ultrasonic transmitter on! By the way, they went out of business after a couple of years.
I didn't read it. just looked at circuitry. Don't know anything about charging insulation.
-RM
I don't know how popular they are, but a few companies have made devices that use ultrasonics to prevent teens from loitering.
I know a man who was audiophile at LLNL (Bob Jones) and he could hear the alarm system also. Drove him nuts when he went into store and they left it on day and night because many couldn't hear it and those who did, did not know what it was. he would walk in and hear it and go to store manager and tell him they forgot to turn alarm off in the morning when they opened for business. They would check and then turn it off.
Many people hear things others can not... So, I include that minority in design considerations so that all are happy. That is part of what makes this the High-End.
-RM
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from your linked Wiki article
I would not call this accepted science. I can hear teenage repellents. I can only assume that makes them offensively loud, not that I can pick up 17kHz. I note that newer ones have 8kHz mixed in so parents don't sue for deafening babies.
But 17kHz at 108dB is not something I would expect in my listening room...
The question would be, what U/S content is there in recorded material?
If none can be found, then what would distinguish a high bw amp?
There are two entry paths for U/S, ears and eyes. Eyes have a band pass function, 25 kHz to 60 kHz with a 30dB coupling loss. Acrylic glasses kill that by reflection, which is another confounders as is where the head is turned to. So even if there were unintended harmonics being generated by the system, it's still down there.
The fact that a study found a physiological response to U/S sound doesn't necessarily mean we hear it.
Edit: whoa, 108 dB? That's well over OSHA. U/S exposures at that level now would be considered illegal due to the untoward biological effects on humans.
Jn
Anyone interested, Google; Eyes as finest rations (fenestrations) to the ears, Lenhardt, 2007..
(I left what my IPad kept trying to change that word into, auto spell garbage kills me.) finest rations indeed!
His reference section is a goldmine. Much of it is from the 40's and 50's.
If none can be found, then what would distinguish a high bw amp?
There are two entry paths for U/S, ears and eyes. Eyes have a band pass function, 25 kHz to 60 kHz with a 30dB coupling loss. Acrylic glasses kill that by reflection, which is another confounders as is where the head is turned to. So even if there were unintended harmonics being generated by the system, it's still down there.
The fact that a study found a physiological response to U/S sound doesn't necessarily mean we hear it.
Edit: whoa, 108 dB? That's well over OSHA. U/S exposures at that level now would be considered illegal due to the untoward biological effects on humans.
Jn
Anyone interested, Google; Eyes as finest rations (fenestrations) to the ears, Lenhardt, 2007..
(I left what my IPad kept trying to change that word into, auto spell garbage kills me.) finest rations indeed!
His reference section is a goldmine. Much of it is from the 40's and 50's.
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The second link, do you not agree, too?
(At age 25 years old, I have medical test. The result said, I can hear 19kHz tone).
Some people like distortion, some people like RFI, we can be certain they aren't liking the music, cuz it ain't there
I would expect that the higher the bw of the amp, the better control over ITD, which is significant to imaging.
Jn
Can you notice the different of cymbal sound with and without sound system?
How can you design an amplifier with low THD at high frequency and low IMD with full power bandwidth below 50kHz?
Maybe you like distortion at high frequency or high IMD
That's hard to say, presuming I could hear 20kHz, would I be able to hear it distorting?Maybe you like distortion at high frequency or high IMD
You wouldn't necessarily need to hear 20kHz. Harmonic distortion of 20kHz you can't hear, but if there are two tones then the same nonlinearity that produces HD will also produce IMD which gives sum and difference frequencies. It should not be impossible for difference frequencies to be where you can hear them.
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How is the limit weighted by frequency? Devices like the Audio Spotlight use far higher levels than that but at very high frequency. IIRC we're talking 160db+
Audio Spotlight by Holosonics - Focused Audio Technology
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Yes, it's not the frequencies at 40kHz which we can sense, which is what was said
@jn I timed out above. I can only find the frequencies used 65-75kHz. I only mention this because I helped the inventor get some free DSP boards and software from Analog so he could finish his thesis and I got a demo of the original prototypes. I was skeptical at the time that there was no data on the effects of ultrasound at these levels. The device works by creating a tight modulated (very complex maths) ultrasound beam that is demodulated into audio by the weak non-linearity of air. As I said the amplitude of the ultrasound was VERY large.
The Japanese tried to make speakers in the 80's but as you can imagine the fidelity and SPL of the demodulated audio is limited (the original demo certainly was). Great for museums where you only hear the description of what you are looking at when you are standing right in front of it while the next display has it's own track with no cross-bleeding.
The Japanese tried to make speakers in the 80's but as you can imagine the fidelity and SPL of the demodulated audio is limited (the original demo certainly was). Great for museums where you only hear the description of what you are looking at when you are standing right in front of it while the next display has it's own track with no cross-bleeding.
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You did not read "high IMD" of my comment
Ultrasonic hearing is debatable, although I give a link of scientific research that show an activity of human brain affected by ultrasonic sound. I see a double standard here.
Except NFB kills the difference frequency. Hence my point that higher THD at 20kHz is not necessarily a bad thing. Low feedback at 1kHz however is!
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