I would like to do noise canceling that works in real time and does not allow microphones and computers to trace the canceled signal. Is it possible or is it useless to waste time as it is always possible to filter? Thanks

That is the original message.
The answer is "NO it is NOT possible, It is a useless waste of time".
QED.

 

There are alternatives to sound cancelling, Those include masking and spoofing. Masking uses a sound source that produces the same frequencies as the sound to be masked, but the level of the produced frequencies is constantly changing, so they are very difficult for a computer system to filter out. The result being that the protected sound is not unmasked and understood. "Spoofing" is more complex in that it delivers what sounds like speech, but that contains no correct information. It is more like the noise in a crowded busy restaurant, but with the frequency adjusted to closely match the sound to be hidden.

 

In any case, the TS is almost certainly looking for a solution to an imaginary problem.

 

I don't think you really understand the principal of noise cancellation. The sound can only be cancelled right at the location where it is to be detected, i.e. at the microphone on the computer that you mention. Then a 180 degrees out of phase signal is generated at that point to cancel it.
Exactly, I need this! Are you sure it really can't be done? because in this video the source of the signal generating destructive interference is placed close to the source of the signal to be canceled.

Did you watch this video? If so, did you ignore that Medhi‘s conclusion as it is impossible?
The device failed every test and part of his explanation of why it can’t work is the incoherence of sound.

Once the sound waves have travelled far enough to be a substantial part of the wavelength they will be spread out and appear to have a source parallel to the listener. Any difference in distance or amplitude of the cancelling signal with reduce the effectiveness to the point of uselessness because the whole enterprise depends on accurately maintaining phase angle so that the cancelling signal stays 180° out of phase with the source.

You can’t do this in a real room with varying path lengths and reflections by generating the signal at the source unless that signal is being generated within a very tiny distance of the source—the same as receiving side cancellation. The bottom line that if you can hear something, and it is possible for someone distant to hear that same thing, they will.

So if you can cancel your heartbeat sound such that you don’t hear it in a stethoscope, you’ve done it. Otherwise, you will still be radiating audible sound. Now, not to complicate things, and bear in mind that this is entirely impractical, if you knew the exact location of the listener and had a huge amount of compute power on hand, and possibly (one or more) phased array(s) of ultrasonic transducers, you could produce an interfering sound that appears precisely at the listeners position.

I suspect, though, that the final “miniaturized” version that no longer needs a large lab cart and to be plugged in would still attract a great deal of attention. Most people don’t walk around with a steerable array of some kind mounted on a mast above their head. Perhaps you could take a clue from the cell phone companies and camouflage the array. A pine tree wouldn’t really be much better… maybe a flagpole, you would look very patriotic… no, that‘s probably just as bad.

I know—a slightly oversized hat! Maybe like this one:

​

A little nonchalance could carry that off.

Seriously though—this is not to make fun of you, or at your expense. I am trying to get past your filter. You have decided that, first, someone is trying to listen to your heartbeat covertly (I don’t care why, it’s a rabbit hole of faulty assumptions, and a festival of confirmation bias), then, second, that this method of preventing it should work.

Everyone is telling you it won’t work but you—though you aware of your naïveté concerning the physics of the situation—are only looking for, and only willing to accept, an answer that matches your preconceived notion that is will.

It won’t, and for that matter, regardless of the number of microphones connected to computers, you can’t hear what isn’t there. The problem is a practical one involving the noise floor and the possible dynamic range for the receiving system. It just won’t work. Just as if you can hear it than anyone else who could hear it would, they can’t hear things that have so little energy where they are they are overwhelmed by other signals.

It is possible to use digital techniques to improve the signal to noise ratio of a target sound? Surely. Is the sound of a heartbeat in an ordinary room (not an anechoic chamber, or one with fixed geometry) audible at any appreciable distance—no.

Just like you needing cart loads of gear to even try to do something “with computers” to make the thing they already can’t do impossible they would need their own cartloads to do something that—like you—requires them to have the ability to use very narrow beam spread to isolate the target. Something like parabolic reflectors or shotgun microphones. In other words, if you see someone with a really big had pretending to ignore you, then you can start to be concerned.

You came, it seemed to ask a question, but you aren’t willing to accept the answers because they aren’t the ones you want. But I fear—and this is a sincere sentiment—that you are asking the wrong questions. You need to ask the questions that should have occurred to you long ago in this train of thought about the listeners and their reality not how to stop someone who isn’t and won‘t be there.

I wish you the very best of luck in dealing with this. I hope you have a quick and positive resolution.

​

 

Did you watch this video? If so, did you ignore that Medhi‘s conclusion as it is impossible?
The device failed every test and part of his explanation of why it can’t work is the incoherence of sound.

Once the sound waves have travelled far enough to be a substantial part of the wavelength they will be spread out and appear to have a source parallel to the listener. Any difference in distance or amplitude of the cancelling signal with reduce the effectiveness to the point of uselessness because the whole enterprise depends on accurately maintaining phase angle so that the cancelling signal stays 180° out of phase with the source.

You can’t do this in a real room with varying path lengths and reflections by generating the signal at the source unless that signal is being generated within a very tiny distance of the source—the same as receiving side cancellation. The bottom line that if you can hear something, and it is possible for someone distant to hear that same thing, they will.

So if you can cancel your heartbeat sound such that you don’t hear it in a stethoscope, you’ve done it. Otherwise, you will still be radiating audible sound. Now, not to complicate things, and bear in mind that this is entirely impractical, if you knew the exact location of the listener and had a huge amount of compute power on hand, and possibly (one or more) phased array(s) of ultrasonic transducers, you could produce an interfering sound that appears precisely at the listeners position.

I suspect, though, that the final “miniaturized” version that no longer needs a large lab cart and to be plugged in would still attract a great deal of attention. Most people don’t walk around with a steerable array of some kind mounted on a mast above their head. Perhaps you could take a clue from the cell phone companies and camouflage the array. A pine tree wouldn’t really be much better… maybe a flagpole, you would look very patriotic… no, that‘s probably just as bad.

I know—a slightly oversized hat! Maybe like this one:

View attachment 311674
​

A little nonchalance could carry that off.

Seriously though—this is not to make fun of you, or at your expense. I am trying to get past your filter. You have decided that, first, someone is trying to listen to your heartbeat covertly (I don’t care why, it’s a rabbit hole of faulty assumptions, and a festival of confirmation bias), then, second, that this method of preventing it should work.

Everyone is telling you it won’t work but you—though you aware of your naïveté concerning the physics of the situation—are only looking for, and only willing to accept, an answer that matches your preconceived notion that is will.

It won’t, and for that matter, regardless of the number of microphones connected to computers, you can’t hear what isn’t there. The problem is a practical one involving the noise floor and the possible dynamic range for the receiving system. It just won’t work. Just as if you can hear it than anyone else who could hear it would, they can’t hear things that have so little energy where they are they are overwhelmed by other signals.

It is possible to use digital techniques to improve the signal to noise ratio of a target sound? Surely. Is the sound of a heartbeat in an ordinary room (not an anechoic chamber, or one with fixed geometry) audible at any appreciable distance—no.

Just like you needing cart loads of gear to even try to do something “with computers” to make the thing they already can’t do impossible they would need their own cartloads to do something that—like you—requires them to have the ability to use very narrow beam spread to isolate the target. Something like parabolic reflectors or shotgun microphones. In other words, if you see someone with a really big had pretending to ignore you, then you can start to be concerned.

You came, it seemed to ask a question, but you aren’t willing to accept the answers because they aren’t the ones you want. But I fear—and this is a sincere sentiment—that you are asking the wrong questions. You need to ask the questions that should have occurred to you long ago in this train of thought about the listeners and their reality not how to stop someone who isn’t and won‘t be there.

I wish you the very best of luck in dealing with this. I hope you have a quick and positive resolution.

​

I guess we say the same thing using different words.

 

I guess we say the same thing using different words.

Yes, and my post includes a giant hat.

 

I already suggested two schemes as alternative to cancelling, which are masking and spoofing. Both achieve-able in a reasonable manner.

 

No, you didn’t read the original question. He is not asking for a way to read the heartbeat, he is asking for a way to by someone from doing that by acoustic means. You answer is to a question that no one asked.

Ok I see where the confusion came in from. Thanks for pointing that out.

What I was getting at at first was that you can't prevent someone from doing that if they are not using acoustic means. If they are using an IR laser then an audio method would not do anything at all.

 

Ok I see where the confusion came in from. Thanks for pointing that out.

What I was getting at at first was that you can't prevent someone from doing that if they are not using acoustic means. If they are using an IR laser then an audio method would not do anything at all.

Don't give him ideas!

Pretty much everyone has the equipment to test the theory that sound can be cancelled at the source. Put your stereo speakers right next to each other. Switch the wiring on one. Play a variety of sounds. Are they cancelled?

Spoiler: High sounds are barely affected. Low sounds are reduced noticeably, but nowhere near cancelled. If the low sounds are enhanced, leave the new wiring, the old wiring was reversed.

 

I already suggested two schemes as alternative to cancelling, which are masking and spoofing. Both achieve-able in a reasonable manner.

They could never achieve what the TS is asking for because the premise on which it is based is imaginary. If masking would work, then environmental noise is already working, if spoofing could work, then everyone else in the room is already providing that service.

If the TS is in a quiet room, with multiple planted microphones doing digital analysis in real time to detect and analyze his heartbeat, then we are in an alternative universe and all bets are off.

 

If the TS is in a quiet room, with multiple planted microphones doing digital analysis in real time to detect and analyze his heartbeat, then we are in an alternative universe and all bets are off.

Perhaps the TS is Vladimir Putin, and the listener is the CIA. That is the most credible scenario I can think of where the premise is true.

 

Perhaps the TS is Vladimir Putin, and the listener is the CIA. That is the most credible scenario I can think of where the premise is true.

If this is Putin, my alternative universe scenario is in force.

 

Don't give him ideas!

Pretty much everyone has the equipment to test the theory that sound can be cancelled at the source. Put your stereo speakers right next to each other. Switch the wiring on one. Play a variety of sounds. Are they cancelled?

Spoiler: High sounds are barely affected. Low sounds are reduced noticeably, but nowhere near cancelled. If the low sounds are enhanced, leave the new wiring, the old wiring was reversed.

Hello again Bob,

What do you mean by 'don't give him ideas' ?

All I am saying is if you try to 'cancel' or reduce a signal that you presume is only going to be audio and it turns out it is not audio, whatever you build isn't going to work.

In this case he is talking about a heartbeat being detected by someone else or computer. He assumes it will always be detected using an audio sensor such as a microphone. Thus, he builds an audio filter of some kind, and maybe it works well. The problem is, it will not stop someone using an IR laser technology to sense the heartbeat. That means someone can still detect his heartbeat, and therefore the audio technique was not effective enough.
It's ok however if he can live with that but if he has no idea that it may not be audio, he will be in for a surprise.

If the solution is to also build some sort of IR shield, then so be it, but without the knowledge of the IR technology he would never think to do that. So that would be what you may call "ideas".