[mriver8 (OP)]

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.

[alancalverd]

You could try active noise-cancelling headphones.

[mriver8 (OP)]

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?

[evan_au]

Much more cheaply (and lighter), a wall composed of foam packing sheets would prevent an ultrasound cannon from reaching the target.

[alancalverd]

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.

[RD]

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.

[mriver8 (OP)]

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.

[mriver8 (OP)]

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.

[alancalverd]

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.

[evan_au]

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...

[mriver8 (OP)]

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.

[mriver8 (OP)]

What about piezo materials?

[mriver8 (OP)]

What about silica sand?

[evan_au]

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.

[alancalverd]

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." 

[evan_au]

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).

[alancalverd]

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

[evan_au]

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

[evan_au]

Seriously, you should talk to your doctor about this.

There are medications today that can attenuate the impact of external sources on your thoughts.

[mriver8 (OP)]

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.