possible to make directional infrasound from a small device?

[Bob Fnord]

Is it possible to produce infrasounds (in the 7 to 20 Hz
range) with a small (coat pocket size) electronic device?
For example, can a small speaker produce such low sounds?

And if so, is it possible to use a reasonably small
parabolic reflector to aim them?


(I have a feeling the answer to both is no.)

 

[Sjouke Burry]

Is it possible to produce infrasounds (in the 7 to 20 Hz
range) with a small (coat pocket size) electronic device?
For example, can a small speaker produce such low sounds?

And if so, is it possible to use a reasonably small
parabolic reflector to aim them?


(I have a feeling the answer to both is no.)

Follow your feeling.

 

[Dirk Bruere at NeoPax]

To have reasonable directivity, the size of the emitter needs to be
large with respect to wavelength. At 12 Hz, you have about 28 m
wavelength in air. So a small (hand held) device will not produce a
narrow beam when emitting 7...20 Hz audio in air.

You can compare your situation with radar antennas. Look to the "old"
HF over the horizon radar systems (OTH radar).

Best regards,

Wim
PA3DJS
www.tetech.nl

It might be possible if high power compression (shock) waves were
directed at 7 per second. But not sinusoid.

--
Dirk

http://www.neopax.com/technomage/ - My new book
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show

 

[Dirk Bruere at NeoPax]

Interestingly you can make a highly directive emitter with a
subwavelength structure, provided it's resonant. Schelkunoff wrote a
paper back in the 1930s about how to do it with antennas.

Google "electrically small antennas".

They're not noted for extreme efficiency, however.

Resonant loops, as used in crystal radios, are also electrically small
antennas--their effective area is increased by a factor of (I think) Q**2.

Cheers

Phil Hobbs

I think Bill Beatty at amasci.com has a lot on that topic IIRC

--
Dirk

http://www.neopax.com/technomage/ - My new book
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show

 

[Dirk Bruere at NeoPax]

Why would you want to do that?

John

Same reason I wanted to do this when I was 16 - to blast people into jelly.

--
Dirk

http://www.neopax.com/technomage/ - My new book
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show

 

[Rich Grise]

Same reason I wanted to do this when I was 16 - to blast people into
jelly.

Why screw around with sound? Just check with your friendly local
neighborhood Jihadist, and learn to make IEDs.

Good Luck!
Rich

 

[Dirk Bruere at NeoPax]

Why screw around with sound? Just check with your friendly local
neighborhood Jihadist, and learn to make IEDs.

I used to do that as well.
Quite a bit better than most amateur terrorists these days.
Back then it was schoolboy fun, not major crime.

--
Dirk

http://www.neopax.com/technomage/ - My new book
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show

 

[hamilton]

Why screw around with sound? Just check with your friendly local
neighborhood Jihadist, and learn to make IEDs.

Good Luck!
Rich

I think the OP is interested in the results of infrasound, as in:
http://en.wikipedia.org/wiki/Infrasound


This may be what the OP is really after: ThinkGeek Annoy-a-tron

http://www.thinkgeek.com/gadgets/electronic/8c52/

hamilton

 

[TheGlimmerMan]

Is this what the tin foil hat brigade is on about?

Ask your friends in the KOOK group, you KOOK bastard.

 

[Dirk Bruere at NeoPax]

Hello Phil,

You are right, it is surprising toe see then when you try to cancel
most of the radiation from an electrically small array (by playing
with phase and amplitude), you can have a direction where the
canceling is not that large anymore (so you have directivity).

The Q factor issue will very likely be present for audio also as the
transducers in the array must cancel most of the sound pressure
produced by the transducers. This will result in local sound pressure
far beyond what a gas at 1 Bar can support, I think.

Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me.

Phased ultrasound arrays in air are quite do-able, and are in fact used
in some types of non-lethal area denial weapons.

BTW, air can support almost arbitrary pressures as long as they are not
negative.

--
Dirk

http://www.neopax.com/technomage/ - My new book
http://www.transcendence.me.uk/ - Transcendence UK
http://www.blogtalkradio.com/onetribe - Occult Talk Show

 

[TheGlimmerMan]

Why are you so cranky about this, Archie?

Go away, you retarded KOOK bastard.

 

[Bob Fnord]

It might be possible if high power compression (shock) waves were
directed at 7 per second. But not sinusoid.

Not square waves from a small multivibrator either,
I guess?

 

[Dirk Bruere at NeoPax]

Not square waves from a small multivibrator either,
I guess?

Probably, since they approximate shock waves and have high frequency
components