Architectural sound enhancement with pre-filtered masking sound

• US 20030144848A1
• Filed: 03/28/2002
• Published: 07/31/2003
• Est. Priority Date: 01/31/2002
• Status: Active Grant

• Current Assignee: AWI Licensing LLC (Armstrong World Industries Incorporated)
• Original Assignee: AWI Licensing Company (Armstrong World Industries Incorporated)
• Inventors: Roy, Kenneth P., Dove, Steve, Johnson, Thomas J., Fuller, Ronald
• Granted Patent: US 7,548,854 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10K 11/1754 Speech masking
• CPC Class Codes: H04K 2203/12 for acoustic communication
• CPC Class Codes: H04K 2203/34 involving multiple cooperating jammers
• CPC Class Codes: H04K 3/42 characterized by the control of the jamming frequency or wavelength
• CPC Class Codes: H04K 3/825 by jamming
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F
• CPC Class Codes: H04S 3/00 Systems employing more than two channels, e.g. quadraphonic H04S5/00, H04S7/00 take precedence

Abstract

A unique, fully integrated, fully programmable, and highly flexible sound distribution system and methodology for providing masking sound, background music, and paging capabilities in up to eight zones of a building or space is provided. The methodology embodied in the system includes internal masking sounds that are uniquely pre-filtered to provide efficient and effective masking of distracting sounds within selectable zones of the space with a minimum masking sound dB sound level and with a pleasant sounding and non-annoying masking sound. The system also incorporates the capacity to be controlled from a remote or local telephone to adjust the volume level in any zone serviced by the system by issuing appropriate DTMF codes from the telephone'"'"'s keypad. Unique bi-tone diagnostic functions are provided for assuring that the entire system is correctly wired and installed and for troubleshooting operational anomalies. ⅓ octave equalization is provided to compensate for known frequency response characteristics of the flat panel radiators of the system and to compensate for varying room acoustics to provide a low special variation of sound among the various zones of the space. The result is a high quality high fidelity sound that is consistent from zone to zone.

Claims

1. A method of producing masking sound within a space for masking distracting noise and providing enhanced speech privacy within the space, said method comprising the steps of:

(a) providing at least one transducer arranged to project sound directly into the space;

(b) determining a desired spectrum for masking sound to be produced within the space;

(c) producing a first noise signal;

(d) subjecting the first noise signal to a pre-filter having substantially the same spectrum as the desired spectrum determined in step (b) to produce a first masking signal;

(e) amplifying the first masking signal; and

(f) driving the at least one transducer with the amplified first masking signal to produce within the space a first masking sound having substantially the desired spectrum determined in step (b).

2. The method of claim 1 and wherein the first noise signal produced in step (c) is a white noise signal.

3. The method of claim 1 and wherein the first noise signal produced in step (c) is a pink noise signal.

6. The method of claim 1 and wherein:

step (c) further comprises producing a second noise signal that is uncorrelated with the first noise signal;

step (d) further comprises subjecting the second noise signal to a filter having substantially the same spectrum as the desired spectrum determined in step (b) to produce a second masking signal;

step (e) further comprises amplifying the second masking signal; and

step (f) further comprises driving at least one transducer within the space with the amplified second masking signal to produce within the space a second masking sound having substantially the desired spectrum determined in step (b), the second masking sound being uncorrelated with the first masking sound to minimize sonic interference between the first and second masking sounds.

7. The method of claim 6 and wherein the second noise signal is a white noise signal.

8. The method of claim 6 and wherein the second noise signal is a pink noise signal.

9. The method of claim 1 and wherein the desired spectrum and the spectrum of the pre-filter have substantially constant negative dB slopes within a predetermined frequency range.

10. The method of claim 9 and wherein the desired spectrum and the spectrum of the pre-filter have slopes of between about −

2 dB per octave and about −

6 dB per octave within the predetermined frequency range.

11. The method of claim 10 and wherein the desired spectrum and the spectrum of the pre-filter have slopes of about −

4 dB per octave within the predetermined frequency range.

12. The method of claim 9 and wherein the predetermined frequency range corresponds substantially to the frequency range of human speech.

13. The method of claim 9 and wherein the predetermined frequency range is between about 200 Hz and about 5000 Hz.

14. The method of claim 13 and wherein the pre-filter has skirt regions outside the predetermined frequency range and wherein the pre-filter falls off within the skirt regions at a predetermined dB rate.

15. The method of claim 14 and wherein the pre-filter falls off by at least 12 dB per octave within the skirt regions.

16. The method of claim 1 and wherein the desired spectrum in step (b) falls within a predetermined frequency range.

17. The method of claim 16 and wherein the predetermined frequency range is substantially the frequency range of human speech.

4. The method of 1 and wherein the at least one transducer is a flat panel sound radiator.

5. The method of claim 4 and wherein the flat panel sound radiator is mounted within a suspended ceiling grid of the space.

18. A method of generating a masking signal to be amplified and reproducing in a space to mask distracting sounds and enhance speech privacy within the space, said method comprising the steps of:

(a) receiving a noise signal; and

(b) pre-filtering the source noise with a pre-filter having a substantially constant negative dB slope within a predetermined frequency range to produce the masking signal.

19. The method of claim 18 and wherein the noise signal is white noise.

20. The method of claim 18 and wherein the noise signal is pink noise.

21. The method of claim 18 and wherein the pre-filter has a slope within the predetermined frequency range of between about −

2 dB per octave and about −

6 dB per octave.

22. The method of claim 21 and wherein the pre-filter has a slope of about −

4 dB per octave.

23. The method of claim 18 and wherein the predetermined frequency range substantially corresponds to the frequency range of the human voice.

24. The method of claim 21 and wherein the predetermined frequency range is between about 200 Hz and about 5000 Hz.

25. The method of claim 24 and wherein the pre-filter falls off at a rate of at least 12 dB per octave within skirt regions outside the predetermined frequency range.

26. In a masking sound system wherein masking signals are amplified and reproduced within a space through flat panel radiators mounted within the suspended ceiling system of the space, a method of improving the efficiency of the system for masking distracting sounds and enhancing speech privacy while reducing the annoying characteristics of the masking sound within the space, the method comprising subjecting the masking signals to a pre-filter having a substantially constant negative dB slope within a frequency range substantially corresponding to the frequency range of human speech.

27. The method of claim 26 and wherein the pre-filter has a slope of between about −

2 dB per octave and about −

6 dB per octave.

28. The method of claim 27 and wherein the filter has a slope of about −

4 dB per octave.

29. A method of producing masking sound in a space having a predetermined desired spectrum effective for masking distracting noises and enhancing speech privacy within the space, said method comprising the steps of mounting an audio transducer to project sound directly into the space, generating a masking signal with a spectrum substantially the same as the predetermined desired spectrum, amplifying the masking signal, and driving the audio transducer with the amplified masking signal to produce masking sound having the predetermined desired spectrum.

30. The method of claim 29 and wherein the audio transducer is a flat panel sound radiator.

31. The method of claim 30 and wherein the flat panel sound radiator is mounted within a suspended ceiling grid of the space.

32. The method of claim 29 and wherein the predetermined desired spectrum has a substantially constant negative dB slope within a selected frequency range.

33. The method of claim 32 and wherein desired spectrum has a slope from about −

2 dB to about −

6 dB per octave within the selected frequency range.

34. The method of claim 33 and wherein the desired spectrum has a slope of about −

4 dB per octave within the selected frequency range.

35. The method of claim 29 and wherein the predetermined desired spectrum falls within a selected frequency range.

36. The method of claim 35 and wherein the selected frequency range is substantially the frequency range of human speech.

37. The method of claim 35 and wherein the selected frequency range is between about 200 and about 5000 Hz.

38. The method of claim 29 and wherein the step of generating a masking signal comprises the steps of generating a noise signal and subjecting the noise signal to a pre-filter having a spectrum substantially the same as the predetermined desired spectrum.