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  4. What type of technology can deflect or block high powered acoustics?
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What type of technology can deflect or block high powered acoustics?

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Offline mriver8 (OP)

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What type of technology can deflect or block high powered acoustics?
« on: 08/01/2015 16:15:59 »
http://sara.com/DE/high_power_acoustics/high_power_acoustic_tech.html

I specifically need to construct a helmet myself but I must do it for under $300.
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Offline alancalverd

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Re: What type of technology can deflect or block high powered acoustics?
« Reply #1 on: 08/01/2015 17:25:35 »
You could try active noise-cancelling headphones.
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Offline mriver8 (OP)

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Could a wall of piezo materials, like barium titanate or PVDF, stop sound?
« Reply #2 on: 08/05/2015 19:23:32 »
Could a wall of piezo materials, like barium titanate or PVDF, act as a shield preventing ultrasound directed through the air from reaching a target? See the attached diagram and assume the wall was instead constructed of piezo materials. Would a wall contructed of such material be enough? Or would it need a layer of piezo material, and other construction elements in your opinion?

* sound_cannon_2.jpg (14.98 kB, 430x234 - viewed 426 times.)
« Last Edit: 10/05/2015 21:40:38 by evan_au »
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Offline evan_au

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #3 on: 08/05/2015 23:12:18 »
Much more cheaply (and lighter), a wall composed of foam packing sheets would prevent an ultrasound cannon from reaching the target.
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Offline alancalverd

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #4 on: 08/05/2015 23:34:53 »
Ultrasound in rapidly attenuated in air. Probably no need for a wall at all, and as Evan says, a soft, absorbent material or a dispersive matrix would be more use than an elastic material like barium titanate.
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Offline RD

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #5 on: 09/05/2015 02:23:05 »

It would take something like a the engine of a jet aircraft to demolish a wall.
Even if you could miniaturise the jet so it could be hand-held, the user would be propelled backwards when they activated it , if they could hang on.
« Last Edit: 09/05/2015 02:48:17 by RD »
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Offline mriver8 (OP)

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #6 on: 09/05/2015 04:33:10 »
Quote from: evan_au on 08/05/2015 23:12:18
Much more cheaply (and lighter), a wall composed of foam packing sheets would prevent an ultrasound cannon from reaching the target.

No regular acoustic foam doesn't work. Neoprine and poly rubber for anechoic chambers works a little at about an inch thick but is not enough at that thickness. I should add the wall has to be under 1 inch thick.
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Offline mriver8 (OP)

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #7 on: 09/05/2015 04:35:31 »
Quote from: RD on 09/05/2015 02:23:05

It would take something like a the engine of a jet aircraft to demolish a wall.
Even if you could miniaturise the jet so it could be hand-held, the user would be propelled backwards when they activated it , if they could hang on.

I used the diagram as an example. Assume sound was being projected at a different frequency and intensity and the wall is constructed of a piezo material.
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Offline alancalverd

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #8 on: 09/05/2015 09:41:18 »
Your attacker would be at less risk if he used dynamite, artillery, or a rocket.

Your defender would stand some chance if he knew the frequency and intensity of the sound wave, and had access to Google. You can't solve an unstated problem, but all the engineering data you need for this job is freely available.
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Offline evan_au

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #9 on: 09/05/2015 09:53:07 »
Quote from: mriver8
Neoprene and poly rubber for anechoic chambers works a little at about an inch thick but is not enough

OK, what is your application, and how much attenuation is needed, at what frequencies?

A set of earplugs from your local hardware store is very effective.

The most common exposure to powerful ultrasound is probably for pre-natal imaging of pregnant women. I think a thin layer of foam would be pretty effective at providing privacy for the fetus.

Walking down the street surrounded by a set of spiky pyramids (as found in anechoic chambers) would keep most people away...
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Offline mriver8 (OP)

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Re: What type of technology can deflect or block high powered acoustics?
« Reply #10 on: 10/05/2015 04:35:53 »
Yes that works but headphones don't cover the entire head and wearing headphones on the head all day with sound running isn't practical.
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Offline mriver8 (OP)

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Re: What type of technology can deflect or block high powered acoustics?
« Reply #11 on: 10/05/2015 04:36:29 »
What about piezo materials?
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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #12 on: 10/05/2015 06:00:36 »
What about silica sand?
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Offline evan_au

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #13 on: 10/05/2015 08:06:04 »
Quote from: mriver8
What about silica sand?
You seem to be proposing solutions, without knowing what the problem is...

How about you state your problem, and then solutions will flow.

Unfortunately, if the ultrasound is purely in your head, then no amount of external shielding will protect you.
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Offline alancalverd

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Re: What type of technology can deflect or block high powered acoustics?
« Reply #14 on: 10/05/2015 09:11:52 »
As on your other thread: what is the incoming spectrum and power, and what are your outgoing limits?

Nobody can help you design a solution if you haven't specified the problem, so let's start at the beginning.

In the wise words of my old navigation instructor: "start from where you are, then you won't get lost before you take off." 
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Re: What type of technology can deflect or block high powered acoustics?
« Reply #15 on: 10/05/2015 09:55:27 »
A mouthguard from your local sports store?

This protects a very common route by which ultrasound gets inside your head (and which won't be blocked by a helmet).
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Offline alancalverd

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Re: Could a wall of piezo materials, like barium titanate or PVDF, stop sound?
« Reply #16 on: 10/05/2015 15:07:12 »
Quote from: mriver8 on 10/05/2015 06:00:36
What about silica sand?

Cheese would be better. Difficult to build a wall out of sand, but the original model of the Manchester Ship Canal that was presented to Parliament for funding, was made of cheese and did the job very well. Processed mild cheddar is best
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Offline evan_au

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Re: What type of technology can deflect or block high powered acoustics?
« Reply #17 on: 10/05/2015 21:48:17 »
Due to their similar nature, posts on "Could a wall of piezo materials, like barium titanate or PVDF, stop sound?" (from the same author) have been merged with this thread.

Future posts will carry the title: "What type of technology can deflect or block high powered acoustics?"

- Moderator

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Offline evan_au

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Re: What type of technology can deflect or block high powered acoustics?
« Reply #18 on: 10/05/2015 21:50:21 »
Seriously, you should talk to your doctor about this.

There are medications today that can attenuate the impact of external sources on your thoughts.
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Offline mriver8 (OP)

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Re: Could a wall constructed of piezo materials such as barium titanate, or PVDF?
« Reply #19 on: 11/05/2015 08:02:04 »
Quote from: evan_au on 10/05/2015 08:06:04
Quote from: mriver8
What about silica sand?
You seem to be proposing solutions, without knowing what the problem is...

How about you state your problem, and then solutions will flow.

Unfortunately, if the ultrasound is purely in your head, then no amount of external shielding will protect you.

Ultrasound directed at over 140DB according to citations from various reports. High intensity ultrasound. Specifically at a intensity and freq that damages hair follicles due to friction.
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