What is the best way to shield / jam ultrasound?

[michael93]

TL;DR Summary

Google "Ultrasonic Cross-Device Tracking"

I've downloaded SoniControl and it works somewhat well as a jammer, but I am looking for more options.

I'm trying to shield from / jam Ultrasonic Cross-Device Tracking (uxDT). (See "data over audio" and "data over sound")

Does anyone have any insight?

I am a programmer, and not an physicist/engineer, so my options are somewhat limited (e.g. I cannot build a jammer, unless it is only software).

 

[Baluncore]

I'm trying to shield from / jam Ultrasonic Cross-Device Tracking (uxDT).

You must either absorb, reflect, or randomly scatter, the unwanted sound.
What is the bandwidth of the audio signal you want to keep out.

It is probably easier to detect and locate the source of interference than block it, then you can take direct action against the hostile source.

 

[Drakkith]

Take care with 'jammers'. You typically have to emit a lot more of whatever signal you're wanting to block. For unltrasound, you'd have to emit more ultrasound to keep the receiver from picking up the original signal through all the noise of the 'jamming signal'. This may be a nuisance to animals nearby that can hear in that range.

 

[michael93]

You must either absorb, reflect, or randomly scatter, the unwanted sound.
What is the bandwidth of the audio signal you want to keep out.

It is probably easier to detect and locate the source of interference than block it, then you can take direct action against the hostile source.

I'm thinking 25kHz+. It's inaudible

See:

 

[michael93]

Take care with 'jammers'. You typically have to emit a lot more of whatever signal you're wanting to block. For unltrasound, you'd have to emit more ultrasound to keep the receiver from picking up the original signal through all the noise of the 'jamming signal'. This may be a nuisance to animals nearby that can hear in that range.

Ok. Do you know of any ways to produce this ultrasound with a computer? For what it's worth, the ultrasound I'm trying to block will be at 25kHz+ (inaudible).

I looked at generating noise at a high frequency via python, but I'm not great at audio signal processing and didn't get very far. Here was my code, much of it copied from stackoverflow (I did not know how to tweak my python script to generate inaudible ultrasound noise -- unless I just didn't hear it, but I didn't really have a way to test -- I tried setting the sample rate to 1000000+):

from scipy.io import wavfile from scipy import stats import numpy as np sample_rate = 44100 length_in_seconds = 3 amplitude = 50 noise = stats.truncnorm(-1, 1, scale=min(2**16, 2**amplitude)).rvs(sample_rate * length_in_seconds) wavfile.write('noise.wav', sample_rate, noise.astype(np.int16))

Python is pretty readable for even people who don't know how to code. Might you have any suggestions for this script?

If not, do you have any suggestions for other ways for jamming?

Also, do you have any recommendations for shielding? I saw in this research paper: https://caslab.csl.yale.edu/publications/matyunin2018zeropermission.pdf

that foam helps somewhat. Do you have any other suggestions?

 

[Tom.G]

"What is the best way to shield / jam ultrasound?"​

If "best" means most effective, probably a deep bunker in the middle of a desert or in the middle of a mountain. Or inside a double-walled container with the gap filled with a lossy visco-elastic material and, if the bunker or container is not metal, a Faraday shield around it all.

The first step would be to record the signal(s) in question so you know what you are trying to interfere with or block.

Once you know what you want to stop, you can then generate an effective interfering signal.

For blocking, a search such as:
https://www.google.com/search?q=ultrasonic+absorbers
returns many results.

Either of these of course means you need to receive or at least detect the signal; otherwise you have no idea whether your approach is working.

So the questions arise, how are you detecting signal and what are its characteristics?

Cheers,
Tom

 

[Baluncore]

I don't think there is yet a problem, but make a start now.
1. Get a bat detector, so you can down-convert and hear active ultrasonic data.
2. Dispose of all mobile phones, and all nearby computers.
3. Move any IoT built after this year, at least 25 metres away.
4. Start to train a dog, rats, or mice, to find hidden ultrasonic chirp transmitters.

To jam signals, once they are detected.
5. Continue to use old switching power supplies.
6. Encourage crickets to live in your garden.
7. Get a bat colony to move into the roof of your house.

 

[berkeman]

Thread closed for Moderation...

 

[berkeman]

TL;DR Summary: Google "Ultrasonic Cross-Device Tracking"

I've downloaded SoniControl and it works somewhat well as a jammer, but I am looking for more options.

I'm trying to shield from / jam Ultrasonic Cross-Device Tracking (uxDT). (See "data over audio" and "data over sound")

Does anyone have any insight?

I am a programmer, and not an physicist/engineer, so my options are somewhat limited (e.g. I cannot build a jammer, unless it is only software).

Upon further review, this thread will remain closed. Trying to thwart Ultrasonic Cross-Device Tracking with moderate-power ultrasonic jamming is not a good approach. At the very least there are potential risks to hearing for people being exposed to such US noise:

https://www.health.belgium.be/en/ultrasound-and-high-frequency-sound

I did the Google search you suggested, and there are lots of better ideas for mitigating the UCDT issue, ranging from just turning it off for devices that offer that option, to using simple US shielding (foams, etc.). Please pursue those avenues -- active jamming of anything is not a subject for amateurs.

Thanks to those who responded with helpful info.

https://physics.aps.org/articles/v7/37

https://en.wikipedia.org/wiki/Cross-device_tracking

https://www.komando.com/privacy/prevent-cross-site-tracking/860853/