ultralow/extremely low frequency generator - Page 2 - Electronic Circuits Projects Diagrams Free

ravide · 13th January 2004, 02:38 PM

Dear All,

Below are a few excerpts about low-frequency high energy sound waves.

LFAS

The US Navy is presently experimenting with Low-Frequency Active Sonar (LFAS), a detection device that produces low frequency (100 to 1000 Hz) sound of very high intensity (~ 230 dB). The purpose is to produce sound that reflects from enemy submarines. The lower frequencies can travel for thousands of miles in sea water. Hence, the relected sound can be used to tract submarine movements from a great distance.

Parametric Difference Waves for Low Frequency Acoustic Propagation
Project:SBIR A97-003
Prior research indicates that an array of ultrasonic sources operated with an offset in frequency will produce infrasonic or very low frequency energy. This energy is useful because it is omni-directional, and it propagates well with little absorption.

This approach utilizes modernized pneumatic technology which produces an extremely high-powered ultrasonic source. The resulting frequency generated is precisely controlled such that the desired high power infrasound frequency can be generated at the target by beating two focused ultrasonic sources.

This were just a few indication for the use of very low frequencies.

just to share some info....

cheers

**Nigel Goodwin** · 13th January 2004, 03:32 PM

Quote:

Originally Posted by ravide

The lower frequencies can travel for thousands of miles in sea water.

I think this is the most relevent line :lol:

I don't see as it's possible to measure short distances with low frequencies, if the wavelength of the pulse is longer than the distance being measured you will get the echo back before you've finished sending the pulse.

FrankM · 14th February 2004, 05:17 PM

This site has plans for a low frequency receiver. The concept can be used for a particular frequency range, depending upon the filter design.

http://elfrad.com/index.htm

john1 · 15th February 2004, 12:24 AM

http://www.cnn.com/2000/NATURE/07/28/beached.whales/

...a suspected link between beached whales and powerful
sonar equipment used by the U.S. Navy...

...dead whales were found to have inner ear damage,
which scientists said might have ruined their sense of...

http://seattletimes.nwsource.com/htm...rpoises09.html

...But the study also could not rule out that the porpoises
might have suffered serious, and perhaps fatal, hearing
damage from the loud naval sonar...

http://www.thesunlink.com/redesign/2...l/278996.shtml

...sound waves emitted by powerful sonar, whales and
dolphins fleeing to the surface of the ocean may succumb to
"the bends," according to an international team of
scientists looking into mysterious die-offs of marine
mammals that have occurred in the wake of military
exercises at sea.

...powerful sonic waves in the water literally shake and tear
delicate air-filled tissues in ears and brain, causing bleeding,
disorientation and death...

An extensive study by the National Marine Fisheries Service attributed
the mass die-off to high-intensity sonar, concluding that it caused
bleeding around the inner ears and trauma to the brain and auditory
system.

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13th January 2004, 02:38 PM	(permalink)
ravide	Excerpts... Dear All, Below are a few excerpts about low-frequency high energy sound waves. LFAS The US Navy is presently experimenting with Low-Frequency Active Sonar (LFAS), a detection device that produces low frequency (100 to 1000 Hz) sound of very high intensity (~ 230 dB). The purpose is to produce sound that reflects from enemy submarines. The lower frequencies can travel for thousands of miles in sea water. Hence, the relected sound can be used to tract submarine movements from a great distance. Parametric Difference Waves for Low Frequency Acoustic Propagation Project:SBIR A97-003 Prior research indicates that an array of ultrasonic sources operated with an offset in frequency will produce infrasonic or very low frequency energy. This energy is useful because it is omni-directional, and it propagates well with little absorption. This approach utilizes modernized pneumatic technology which produces an extremely high-powered ultrasonic source. The resulting frequency generated is precisely controlled such that the desired high power infrasound frequency can be generated at the target by beating two focused ultrasonic sources. This were just a few indication for the use of very low frequencies. just to share some info.... cheers __________________ The science of sonic

14th February 2004, 05:17 PM	(permalink)
FrankM	low frequency receiver This site has plans for a low frequency receiver. The concept can be used for a particular frequency range, depending upon the filter design. http://elfrad.com/index.htm

15th February 2004, 12:24 AM	(permalink)
john1	http://www.cnn.com/2000/NATURE/07/28/beached.whales/ ...a suspected link between beached whales and powerful sonar equipment used by the U.S. Navy... ...dead whales were found to have inner ear damage, which scientists said might have ruined their sense of... http://seattletimes.nwsource.com/htm...rpoises09.html ...But the study also could not rule out that the porpoises might have suffered serious, and perhaps fatal, hearing damage from the loud naval sonar... http://www.thesunlink.com/redesign/2...l/278996.shtml ...sound waves emitted by powerful sonar, whales and dolphins fleeing to the surface of the ocean may succumb to "the bends," according to an international team of scientists looking into mysterious die-offs of marine mammals that have occurred in the wake of military exercises at sea. ...powerful sonic waves in the water literally shake and tear delicate air-filled tissues in ears and brain, causing bleeding, disorientation and death... An extensive study by the National Marine Fisheries Service attributed the mass die-off to high-intensity sonar, concluding that it caused bleeding around the inner ears and trauma to the brain and auditory system.