How can you direct a sound at a certain area and how does it work?

Question

The sound device on futre weapons was called LRAD long range acoustic device

Answer 1

Sound is made from vibrations and travels in waves. The waves coming from the usual speakers, which are funnel or cone shaped, are vibrated on a membrane and spread outwards in an increasing arc so they can be heard by anyone within that arc.

The frequency of a sound wave is measured in hertz and it has been found that If the sound waves are disrupted with ultrasonic air waves of about 100,000 hertz, they can be forced not to spread out and focused to travel in a chosen direction. These high frequency or ultrasounds are outside of the frequency range of human hearing, like the sounds of dog whistles which cannot be heard by humans.

Directed sound would enable some standing in front of a vending machine to hear an advertisement while someone standing more than a couple of feet to the side would not be able to hear it. So while it might be great for advertisers I wonder what will happen to the poor dogs that come within range.
You can see an illustration of the method at the site below.

Answer 2

Two ways. One way is in the link by member alpha above (last paragraph).

An other way is to put a sound source next to a beam of ultrasonic sound. The sound travels with the beam.

*note - there are much smaller and more available devices than a LRAD that can do this.

Answer 3

There was a programme on Discovery Channel called "Future Weapons". They had several non leathal weapons to be used in riot situations. One was able to direct sound straight in front if it. It might be repeated on TV or google it to find the name of it. I can't remember.

Answer 4

yes ,bose have made a fortune using wave sound technology ,basically sticking a long tube over the cone of the speaker ,this also amplifies the resonant sound

Answer 5

put your lips as close to his ear as possible and then shout as loud as you can