1. A method for dispersing a first group of people in a human population from a fixed location and preventing the first group of people from loitering in the fixed location, comprising:
- mounting a sound-emitting device to a permanent structure at the fixed location, said sound-emitting device including oscillating means for generating a signal and sounding means for generating and emitting sound in accordance with said signal;
- wherein the sound generated and emitted by said sounding means of said sound-emitting device consists essentially of sound waves in a predetermined frequency band that is no more than 2 kHz in width and encompasses 16.5 kHx, said predetermined frequency band of the sound waves being audible to said first group of people in the human population and substantially inaudible to a second group of people in the human population, whereby said sound emitted by said sounding means of said sound-emitting device operates to disperse said first group of people from said fixed location and to prevent said first group of people from loitering in said fixed location.
2. The method of claim 1, wherein:
- said predetermined frequency band is 16.5 kHz±1 kHz.
3. The method of claim 1, wherein:
- said sounding means includes a transducer.
4. The method of claim 1, wherein:
- said sound is emitted with a directional spread of 50° to 70°.
5. The method of claim 1, wherein:
- said permanent structure is selected from the group including a wall and a post.
6. The method of claim 1, wherein:
- said fixed location includes an area defined by a distance from said sound-emitting device of up to fifteen meters.
7. The method of claim 1, wherein:
- said first group of people are teenagers.
8. The method of claim 1, wherein:
- said device comprises an amplifier and automatic gain control.
9. The method of claim 8, wherein:
- said automatic gain control measures a level of background noise and adjusts an amplitude of the sound so that the amplitude of the sound wave is above the level of the background noise.
10. The method of claim 1, further comprising:
- emitting an indicator periodically to indicate that the device is working.
11. The method of claim 10, wherein:
- said indicator is an audible indicator.
12. A method according to claim 1, wherein:
- said predetermined frequency band consists of frequencies between 15.5 KHz and 17.5 KHz.
13. A method for dispersing a first group of people in a human population from a location, comprising:
- providing a sound-emitting device having oscillating means for generating a signal and sounding means for generating and emitting sound in accordance with said signal;
- wherein the sound generated emitted by said sounding means of said sound-emitting device consists essentially of sound waves in a predetermined frequency band that is no more than 2 kHz in width and encompasses 16.5 kHx, said predetermined frequency band of the sound waves being audible to said first group of people, substantially inaudible to a second group of people in the population and operating to disperse said first group of people from said location.
14. The method of claim 13, wherein:
- said sounding means comprises a transducer.
15. The method of claim 13, wherein:
- said sound is emitted with a directional spread in a range of substantially 50°-70°.
16. The method of claim 13, wherein:
- said location includes an area defined by a distance from said sound-emitting device of up to at least fifteen meters.
17. The method of claim 13, wherein:
- said first group of people are teenagers.
18. The method of claim 13, wherein:
- said device comprises an amplifier and automatic gain control.
19. The method of claim 18, wherein:
- said automatic gain control measures the level of background noise and adjusts an amplitude of the sound so that the amplitude of the sound is above the level of the background noise.
20. The method of claim 13, further comprising:
- emitting an indicator periodically to indicate that the device is working.
21. The method of claim 20, wherein:
- said indicator is an audible indicator.
22. A method according to claim 13, wherein:
- said predetermined frequency band is 16.5 kHz±1 kHz.
23. A method according to claim 13, wherein:
- said predetermined frequency band consists of frequencies between 15.5 KHz and 17.5 KHz.
24. A sound-emitting device, comprising:
- oscillating means for generating a signal; and
- sounding means for generating sound in accordance with said signal, said sound consisting essentially of sound waves in a predetermined frequency band that is no more than 2 kHz in width and encompasses 16.5 kHz, said predetermined frequency band of the sound waves being audible to a first group of people in a human population and substantially inaudible to a second group of people in the human population, the second group of people older than the first group of people, wherein said sound operates to disperse said first group of people away from said sound-emitting device.
25. The sound-emitting device of claim 24, wherein:
- said predetermined frequency band is 16.5 kHz±1 kHz.
26. The sound-emitting device of claim 24, wherein:
- said sounding means emits said sound with a directional spread of sixty ±10°.
27. The sound-emitting device of claim 24, wherein:
- said sound-emitting device is hand-held.
28. The sound emitting device of claim 24, wherein:
- said first group of people are teenagers.
29. The sound-emitting device of claim 24, wherein:
said predetermined frequency band consists of frequencies between 15.5 kHz and 17.5 kHz.
30. A method for dispersing a first group of people in a human population from a location, comprising:
- providing a sound-emitting device at the location, the sound-emitting device having signal generating means for generating an electrical signal and sounding means for generating and emitting sound in accordance with said electrical signal;
- wherein said electrical signal has a first frequency component and a second frequency component, said first frequency component within a first predetermined frequency band that is no more than 2 kHz in width and encompasses 16.5 kHz, and said second frequency component in a second predetermined frequency band between 1 Hz and 10 Hz; and
- wherein said sound emitted by said sounding means comprises sound waves in said first predetermined frequency band that are modulated at one or more low frequencies within said second predetermined frequency band, wherein said modulated sound waves are audible to the first group of people in the human population and are substantially inaudible to a second group of people in the human population, the second group of people older than the first group of people, whereby the modulated sound waves operate to disperse the first group of people away from the location.
31. A method according to claim 30, wherein:
- said first predetermined frequency band consists of frequencies between 15.5 kHz and 17.5 kHz.
32. A method according to claim 30, wherein:
- said second predetermined frequency band consists of frequencies between 1.8 Hz and 5.8 Hz.
33. A sound-emitting device, comprising:
- signal generating means for generating an electrical signal; and
- sounding means for generating and emitting sound in accordance with said electrical signal;
- wherein said electrical signal has a first frequency component and a second frequency component, said first frequency component within a first predetermined frequency band that is no more than 2 kHz in width and encompasses 16.5 kHz, and said second frequency component in a second predetermined frequency band between 1 Hz and 10 Hz; and
- wherein said sound emitted by said sounding means comprises sound waves in said first predetermined frequency band that are modulated at one or more low frequencies within said second predetermined frequency band, wherein said modulated sound waves are audible to a first group of people in a human population and are substantially inaudible to a second group of people in the human population, the second group of people older than the first group of people, wherein the modulated sound waves operate to disperse said first group of people away from said sound-emitting device.
34. A sound emitting device according to claim 33, wherein:
- said first predetermined frequency band consists of frequencies between 15.5 kHz and 17.5 kHz.
35. A sound emitting device according to claim 33, wherein:
- said second predetermined frequency band consists of frequencies between 1.8 Hz and 5.8 Hz.
