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Author Topic: Can ultrasound transmission be blocked?  (Read 7728 times)

Offline bluecrystal48

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Can ultrasound transmission be blocked?
« on: 20/06/2007 21:57:22 »
Please explain the ways in which one can block the transmission of ultrasonic sound. I am especially interested in a cost-effective solution a layman can utilize. Your input will be greatly appreciated. Thank you very much.
« Last Edit: 14/11/2015 09:26:52 by chris »


 

another_someone

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blocking ultrasonic sound
« Reply #1 on: 20/06/2007 23:40:35 »
Ultrasound should be relatively easy to block - infrasound tends to cause the greater problems.  Even a simple brick wall I would have thought would be sufficient to block ultrasound.
 

paul.fr

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blocking ultrasonic sound
« Reply #2 on: 21/06/2007 01:22:07 »
In what circumstances do you want to block ultrasound? As George has said, a brick wall may be sufficient or are you talikg in medical terms?

If medical, try searching the keywords "negative refraction" on google or at the newscientist website...www.newscientist.org, i think.
 

Offline Soul Surfer

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blocking ultrasonic sound
« Reply #3 on: 21/06/2007 10:40:23 »
The answer to your question depends on the conditions what you are doing and why you are trying to do it.  For ultrasound in air simple barriers are enough in solids and liquids you need to put in layers of soft lossy material like putty.
 

Offline deanto

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Re: blocking ultrasonic sound
« Reply #4 on: 14/11/2015 08:12:59 »
The answer to your question depends on the conditions what you are doing and why you are trying to do it.  For ultrasound in air simple barriers are enough in solids and liquids you need to put in layers of soft lossy material like putty.

Hello there,
I am not the OP, and I`m so sorry that i revive this old post. Here is one reason that one could want to block certain ultrasonic (or maybe infrasonic) signals (link form arstechnica.com not allowed)


Brief description:

Cross-device tracking can also be performed through the use of ultrasonic inaudible sound beacons. Compared to probabilistic tracking through browser fingerprinting, the use of audio beacons is a more accurate way to track users across devices. The industry leader of cross-device tracking using audio beacons is SilverPush. When a user encounters a SilverPush advertiser on the web, the advertiser drops a cookie on the computer while also playing an ultrasonic audio through the use of the speakers on the computer or device. The inaudible code is recognized and received on the other smart device by the software development kit installed on it. SilverPush also embeds audio beacon signals into TV commercials which are "picked up silently by an app installed on a [device] (unknown to the user)."

so I`m worried, if all this is true (and i`m not saying it is) what else, beside ads, they can track also...

have a nice day,

Dean
from Bulgaria
 

Offline Colin2B

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Re: blocking ultrasonic sound
« Reply #5 on: 14/11/2015 09:13:18 »
Hi Dean, welcome to the forum.
You might want to repost or copy this post in the geek speak section.
 

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Re: blocking ultrasonic sound
« Reply #5 on: 14/11/2015 09:13:18 »

 

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