Communications: electrical – Audible indication – Ultrasonic pest control
Patent
1995-08-04
1998-02-03
Mullen, Thomas
Communications: electrical
Audible indication
Ultrasonic pest control
3403844, 3403847, 34038472, 367103, 367139, H04N 712
Patent
active
057149267
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method for preventing trespassing and/or unauthorized staying in an area outdoors or indoors, e.g. in a building, part of a building, in vehicles, vessels, and the like.
Prior art alarms installed for protection of property against theft or damage have the disadvantage that the intruder can continue the activity until somebody reacts to the alarm and may thus also have time to finish the activity and leave the place before the alarm personnel reach the place.
There are also noise generating devices which are used for keeping away noxious animals and such, one example being disclosed in the French Patent Publication No 2556485. The device according to this publication can work with several sirens which can work with different frequencies and be controlled separately. It is said that this gives rise to an unbearable sound. However, it has been shown that animals such as rodents can get used to a noise and therefore return to the sound laden area. The device according to this publication is also said to be useful as a protective alarm. The human organ of hearing is however adjustable and also contains protective mechanisms which to a certain extent protect against high sounds, and consequently the usefulness of the means according to the French patent publication is highly unreliable also for this purpose.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and a means for generating sound which is unendurable for humans and/or animals and which makes it impossible to stay within the field of operation of the means.
This is achieved with the method according to the present invention which is characterized in that sound generators transmit sound signals with periodically varying frequencies with the different frequency sound signals emitted by each sound generator being out of phase with respect to the sound signals emitted by the other sound generators in such directions that the sound waves from the sound generators meet within the area to be protected.
According to one embodiment of the invention, sound signals are transmitted with frequencies which periodically rise from and then return to the basic frequency.
According to another embodiment of the invention, sound signals are transmitted with frequencies successively rising from the basic frequency and abruptly falling back to the basic frequency.
According to a further embodiment of the invention the basic frequency for the sound signals are changed after predetermined time intervals. Hereby the risk of somebody quenching the sound signals with the aid of a counter sound generator is avoided.
According to a further embodiment of the invention a phase shift between the sound signals of in the order of milliseconds is used.
According to a further embodiment of the invention a sound level of 110 dB and up is used.
According to a further embodiment of the invention sound signals from at least four sound generators are used. Hereby use is made of the fact that the human organ of hearing possibly can endure three frequencies at the same time through the protective mechanisms, but that further simultaneous sound signals with different frequencies are not endured.
The invention also comprises means for accomplishing the method according to the invention, which is characterized in that it comprises several sound generators with control means for generating sound signals with periodically varying frequencies with the different frequency sounds being out of phase from sounds emitted by the other sound generators, whereby the sound generators are so directed that the sound waves from the sound generators meet within the area to be protected.
According to an embodiment of the means according to the invention the means comprises at least four sound generators.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 graphically illustrates four different sound signals respectively emitted by four different sound generators in accordance with a preferred embodiment of the present inve
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Mannava Ashok
Mullen Thomas
LandOfFree
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