CA1042811A - Process and apparatus for speech privacy improvement through incoherent masking noise sound generation in open-plan office spaces and the like - Google Patents
Process and apparatus for speech privacy improvement through incoherent masking noise sound generation in open-plan office spaces and the likeInfo
- Publication number
- CA1042811A CA1042811A CA240,268A CA240268A CA1042811A CA 1042811 A CA1042811 A CA 1042811A CA 240268 A CA240268 A CA 240268A CA 1042811 A CA1042811 A CA 1042811A
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- noise
- masking
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- incoherent
- sound
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Abstract
Abstract of Disclosure The invention involves the use of a plurality of incoherent noise generators distributed, in one embodi-ment, along ceilings in open-plan and partitioned office spaces and the like, to diffuse masking sound energy through acoustical tile and other false ceiling structures while tailoring the same for speech privacy results.
Description
The present invention relates to sound diffusers for ceilings and similar surfaces, being more particularly directed to providing masking noise distribution in open-plan landscaped and partitioned office spaces and the like to improve speech privacy and for related results.
The problem underlying the preferred application of the invention is to provide throughout open-plan offices, rooms, working spaces and the like, where usually privacy is provided by partial screens and similar devices, but wherein sound can flow between spaces, a spacially uniform masking noise of non-obtrusive, pleasant acoustic quality, tailored to be effective in masking speech sounds and the like at a minimum of cost.
Open-plan spaces are described, for example, in "The Private Office" b~ Ziering, TWA Ambassadors Magazine, May 12, 1973, p.
12. It has been found that a reasonable degree of acoustic pri-vacy can be obtained with high enough intensity background noise, but of unobtrusive character and of frequency spectrum, tailored preferably to resemble wind or waves, as described for example, on p 592 et seq. of "Noise and Vibration Control" Leo L. Beranek, McGraw Hill, 1971. It is believed that such a spectrum prefer-ably has the following relative approximate levels, measured in ~@ .
rw,~`jo 1~4~811 octave bands: 125 Hz-Odb; 250 Hz-3db; 500 Hz-6db; 1000 Hz-lldb;
2000 ~z-18db; 4000 Hz-26db; 8000 Hz-36db. The extent to which the listener localizes the source, of course, is a measure of the obtrusive character of the installation.
Prior approaches to the solution of this problem include a noise-propagating array of loud speakers above the acoustical tiles in a hung acoustical ceiling. (See, for example, "5peech Privacy In Buildings", Journal of the Acoustical Society of America, Vol. 34, p. 475-492, 1962). Since the acoustical lQ transmission loss factors of such ceilings in different buildings widely vary, the electronic system must be turned to provide the desired spectrum. Obstructions and duct work, moreover, can pro-duce non-uniform spacial masking sound distribution. Conventional systems for masking purposes in large open plan spaces, i~deed, customarily employ a centrally located electronic noise generating and amplifying assembly, a complex-loudspeaker transducer power distribution network, and a multiplicity of loudspeakers operating in total or partial acoustical phase coherence and distributed spatially throughout the area of coverage, as described, for -example, in the "Privatalk" catalog of Baldwin-Ehret-Hill, Inc., 1973. The coherence resulting from such rwf ~` - 2 - ~ -.. . .
lf~Z81'~ l speakers connected to the same sound amplifier or other source often creates an undesirable sound-shifting sensation in moving about the space, requiring a plurality of separate distribution systems and incoherent sources, increasing both complexity and cost. Such installations, moreover, require licensed and skilled installers from other trades than the building construction trades per se.
Other approaches have involved the use of aerodynamic-ally driven noise sources connected by flexible tubing to a con-stant pressure air supply source, but again requiring specialequipment in the form of an air supply source and distribution system.
If, moreover, resort is had to the masking noise of the ventilating, heating, or air conditioning system itself, the vari-ations in the ventilating system cause non-uniformity of masking noise and its distribution; and usually uniform distribution is not feasible with the positions selected for such systems.
The present invention relates to a process of distri-buting masking sound in an open-plan space and the like, that comprises, independently and incoherently generating and radiating noise at a plurality of positions laterally separated from one another above a sound-transmitting surface covering such an open space; shaping the frequency spectrum of the noise to correspond substantially to that desired for speech privacy masking; and ad-justing the lateral separation of noise radiation positions from one another to control the diffusion and distribution of the masking noise sound cumulatively transmitted through and below the surface into the open space, in order to provide a uniform, -29 de-localized incoherent masking radiation within the open space~
A mb/~h~ 3 - , . . . . ` . , . ~
In another aspect the present invention relates to apparatus for distributing masking noise through a false ceiling surface and the like into an open space therebelow, having, in combination, a plurality of independent incoherent noise-gener-ating units, each provided with a separate electronic noise source, frequency shaping filter, amplifying and sound radiating means; means for mounting the uni~s at a plurality of positions laterally spaced over the ceiling surface; means for powering the units from ceiling power conduit means; and means for tuning ~-the shaping filter and for adjusting the height of the units above the ceiling surface and adjusting the lateral separation of the units to provide a predetermined speech privacy noise attenuation spectrum below the ceiling surface, the surface be-ing selected to diffuse the noise radiated from the plurality of units to provide cumulative de-localized incoherent masking radiation within the open space.
In a preferred realizatio~ the invention employs a regular pattern of such generator units concea~ed above on acoustical tile ceiling in appropriate position and distribution~
with primary power derived from a dedicated power distribution system or from a power distribution~system intended for other above-ceiling components, such as for lighting fixtures. Maxi-mum delocalization of the sound is achieved as a result of these independent sources, taking advantage of the characteristics of .. ....
the ceiling structure for more uniform distribution of the mask-ing sound. Other distributed installations are also feasible, 28 as later explained.
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.. .... -~.. .. -. - .. -, ................................ ....... - . -- . ;........ .~...... - .......... . .... ........ , ... ~; . ~., . ... ~ .. . .. .... . . .. .. . . ..... ...... ... ... . .. . .. . . . . ...... .... .. ..
In prior art systems, moreover, ~ith loudspeakers disposed above the ceilings to try to reduce localization, the variability in the components in the plenum above the ceiling in the different parts of the building produces tonal variations in the space below obviated by the present invention.
In accordance with the invention, moreover, the radi-ated power level of each unit (1) is independent of components or variable characteristics of the plenum, (2) is easily separ-ately adjustable, and (3) either directly faces into the ro~m 10 - or reflects from the main celling into the room, but with the added automatic distributing and appearance-hiding features of the visible ceiling.
The invention will now be described with reference to the accompanying drawing, Fig. 1 of which is a functional i block diagram of a preferred noise generator unit useful with the invention, Fig. lA is a similar diagram of a transmitter for superimposing upon the masking noise, if desired, coherent in-telligence such as speech messages and/or background music or other signals.
Fig. 2 is a longitudinal section illustrating a method of mounting the units; and Fig. 3 is a plan view, with the false ceiling removed, of a typical distribution of masking generators above an acous-tical ceiling of an open-plan office.
Each of the independent self-contained noise generator units of the invention may be of the form functionally illustrat-ed in Fig. 1, embodying in a single housing, generally designated 29 at 1, a broadband electronic noise source 4 the output of which :'.
,) "
.... .. . . . . .. . .
.. .. :,. ~.. .. -... .. .. - ... - .- ,,,, , . . :. . : -:
i. .. :, i .::, . ,,,~, . : . :. .. , . ., ~
! ` . , . S : ' ' . '. ' . ~ . . . . . . . . , ' ., , ,' . ~ ' ' ... .
" ~''.' ,.' ' ' ' " .'' '., ','' . .;' ;''' ~ ' ' ' ' ' ' . ' ' ' . ' . ' ' " '. ' "'''' '' ' ' ' . . ' ': ~ '; ''" . '' ..
is appropriately frequency-shaped, as before and hereinafter described, in a tunable filter 6-, with the appropriately fre-quency-tailored noise spectrum signal amplitude-adjusted by an attenuator 8 and then amplified at 10 and radiated by a loud-speaker 12. The unit, as previously explained, may be powered at 2, Figs. 1 and 2, from the same power conduits provided for the lighting or other ceiling electric equipment.
mb/~c~D - Sa -'' , ",,, ", , , ,, ,, ,,,, ,, ,,, ,, ,, , ,, , ,, " , , , ,." ,.. .... ... . .. ...
-; . ~.-.. ~,. . .. . . . , ~ , ; . .. , -, . .. . .
As more particularly shown in Fig. 2, the masking generator unit 1 is mountable at variable distances from the main ceiling 3, as by a suspension 5 (which may include the .
power cord 7), or by mounting brac~ets (not shown) connected with conduit junction boxes and the like carried by or from the main ceiling 3. The speaker may point downward or upward, as shown, as desired. Thus control is effected of the position or region of disposition of the unit housing 1 within the .air space between the main ceiling and the sound-transmitting acoustical or other false ceiling surface 3' suspended by struts 5' or otherwise from the main ceiling 3. In this manner, the instal-lation can be effected by the same personnel who install other ceiling structures and from the same power outlets, with flexi-bility for taking advantage of the frequency-tailoring, final-attenuation adjustment and diffusing characteristics of the particular acoustical or other visible ceiling surface 3' or other diffuser at the top of the open space and which serves to transmit the masking noise from the generator units 1 into .
the open space below.
By distributing the plurality of units 1 at appropriate laterally separated positions in the space between the main and f~lse ceiling surfaces 3 and 3', as shown, for example, in Fig. 3, and adjusting the unit heights above the sound-dif-fusing false ceiling surface 3' for appropriate frequency tail-oring or shaping and diffusion, compension can be effected for the frequ~ncy-dependent acoustical power output of the loud-speaker transducer and associated enclosure, for the frequency 28 dependent acoustical noise reduction of the ceiling assembly, and : .
"
~/J~
, - , : - - ~-. .
- 1~4Z1311 for the frequency-dependent contribution of acoustical po~7er from adjacellt generator units 1. ~dditional frequency shaping is employed to limit displacement of the loudspeaker transducer diaphragm at frequencies less than some lower frequency, and for frequencies greater than some higher frequency necessary for effective speech masking, such as of the before-mentioned values. By selecting and/or changin~ appropriate false acoustic ceiling tiles or panels 3', of different porosity or other prop~
erties, or providing metal or other diffuser baffle structures including fluorescent or other light diffusing structures, tail-oring or shaping of diffusion and spreading characteristics can be attained.
In a typical installation of the type shown in Fig. 3, the units 1 were spaced in ro~Js and columns about 12 feet apart, and suspended within a ceiling space (between 3 and 3') about
The problem underlying the preferred application of the invention is to provide throughout open-plan offices, rooms, working spaces and the like, where usually privacy is provided by partial screens and similar devices, but wherein sound can flow between spaces, a spacially uniform masking noise of non-obtrusive, pleasant acoustic quality, tailored to be effective in masking speech sounds and the like at a minimum of cost.
Open-plan spaces are described, for example, in "The Private Office" b~ Ziering, TWA Ambassadors Magazine, May 12, 1973, p.
12. It has been found that a reasonable degree of acoustic pri-vacy can be obtained with high enough intensity background noise, but of unobtrusive character and of frequency spectrum, tailored preferably to resemble wind or waves, as described for example, on p 592 et seq. of "Noise and Vibration Control" Leo L. Beranek, McGraw Hill, 1971. It is believed that such a spectrum prefer-ably has the following relative approximate levels, measured in ~@ .
rw,~`jo 1~4~811 octave bands: 125 Hz-Odb; 250 Hz-3db; 500 Hz-6db; 1000 Hz-lldb;
2000 ~z-18db; 4000 Hz-26db; 8000 Hz-36db. The extent to which the listener localizes the source, of course, is a measure of the obtrusive character of the installation.
Prior approaches to the solution of this problem include a noise-propagating array of loud speakers above the acoustical tiles in a hung acoustical ceiling. (See, for example, "5peech Privacy In Buildings", Journal of the Acoustical Society of America, Vol. 34, p. 475-492, 1962). Since the acoustical lQ transmission loss factors of such ceilings in different buildings widely vary, the electronic system must be turned to provide the desired spectrum. Obstructions and duct work, moreover, can pro-duce non-uniform spacial masking sound distribution. Conventional systems for masking purposes in large open plan spaces, i~deed, customarily employ a centrally located electronic noise generating and amplifying assembly, a complex-loudspeaker transducer power distribution network, and a multiplicity of loudspeakers operating in total or partial acoustical phase coherence and distributed spatially throughout the area of coverage, as described, for -example, in the "Privatalk" catalog of Baldwin-Ehret-Hill, Inc., 1973. The coherence resulting from such rwf ~` - 2 - ~ -.. . .
lf~Z81'~ l speakers connected to the same sound amplifier or other source often creates an undesirable sound-shifting sensation in moving about the space, requiring a plurality of separate distribution systems and incoherent sources, increasing both complexity and cost. Such installations, moreover, require licensed and skilled installers from other trades than the building construction trades per se.
Other approaches have involved the use of aerodynamic-ally driven noise sources connected by flexible tubing to a con-stant pressure air supply source, but again requiring specialequipment in the form of an air supply source and distribution system.
If, moreover, resort is had to the masking noise of the ventilating, heating, or air conditioning system itself, the vari-ations in the ventilating system cause non-uniformity of masking noise and its distribution; and usually uniform distribution is not feasible with the positions selected for such systems.
The present invention relates to a process of distri-buting masking sound in an open-plan space and the like, that comprises, independently and incoherently generating and radiating noise at a plurality of positions laterally separated from one another above a sound-transmitting surface covering such an open space; shaping the frequency spectrum of the noise to correspond substantially to that desired for speech privacy masking; and ad-justing the lateral separation of noise radiation positions from one another to control the diffusion and distribution of the masking noise sound cumulatively transmitted through and below the surface into the open space, in order to provide a uniform, -29 de-localized incoherent masking radiation within the open space~
A mb/~h~ 3 - , . . . . ` . , . ~
In another aspect the present invention relates to apparatus for distributing masking noise through a false ceiling surface and the like into an open space therebelow, having, in combination, a plurality of independent incoherent noise-gener-ating units, each provided with a separate electronic noise source, frequency shaping filter, amplifying and sound radiating means; means for mounting the uni~s at a plurality of positions laterally spaced over the ceiling surface; means for powering the units from ceiling power conduit means; and means for tuning ~-the shaping filter and for adjusting the height of the units above the ceiling surface and adjusting the lateral separation of the units to provide a predetermined speech privacy noise attenuation spectrum below the ceiling surface, the surface be-ing selected to diffuse the noise radiated from the plurality of units to provide cumulative de-localized incoherent masking radiation within the open space.
In a preferred realizatio~ the invention employs a regular pattern of such generator units concea~ed above on acoustical tile ceiling in appropriate position and distribution~
with primary power derived from a dedicated power distribution system or from a power distribution~system intended for other above-ceiling components, such as for lighting fixtures. Maxi-mum delocalization of the sound is achieved as a result of these independent sources, taking advantage of the characteristics of .. ....
the ceiling structure for more uniform distribution of the mask-ing sound. Other distributed installations are also feasible, 28 as later explained.
mb/~ 4 A
::
.... . .~. . . .,. ........................ .~,. ... .;.................. . ...... ,.,.. ,i.. ,. ... ,~-. . . .
...., . ...... ., . ..... ..... ~ . . . . - ......................... . ............. ; . ~ .. . . . ..... . ... . ... .
. . ... . . .-.. . .. .. . ~.. . .... -.. . . . .. . .. ..... -. .. -... ; ................. .. . . ........... .. ..... .. . .. ..... ... ..... . . . . . . . . . ......... . . ..... .. . - .. - . . .. .~ . - . - ... - .. .... .. .. . . . .. - . .. .. .. , . ~ . . . .
... . ; ...... . . . .. ~ .. . .. ... . .. .... .. - ........... ...... - .. .. . . ....... ... .... .. ... .. . . .. .... ... . .. .. . .. .
.. .... -~.. .. -. - .. -, ................................ ....... - . -- . ;........ .~...... - .......... . .... ........ , ... ~; . ~., . ... ~ .. . .. .... . . .. .. . . ..... ...... ... ... . .. . .. . . . . ...... .... .. ..
In prior art systems, moreover, ~ith loudspeakers disposed above the ceilings to try to reduce localization, the variability in the components in the plenum above the ceiling in the different parts of the building produces tonal variations in the space below obviated by the present invention.
In accordance with the invention, moreover, the radi-ated power level of each unit (1) is independent of components or variable characteristics of the plenum, (2) is easily separ-ately adjustable, and (3) either directly faces into the ro~m 10 - or reflects from the main celling into the room, but with the added automatic distributing and appearance-hiding features of the visible ceiling.
The invention will now be described with reference to the accompanying drawing, Fig. 1 of which is a functional i block diagram of a preferred noise generator unit useful with the invention, Fig. lA is a similar diagram of a transmitter for superimposing upon the masking noise, if desired, coherent in-telligence such as speech messages and/or background music or other signals.
Fig. 2 is a longitudinal section illustrating a method of mounting the units; and Fig. 3 is a plan view, with the false ceiling removed, of a typical distribution of masking generators above an acous-tical ceiling of an open-plan office.
Each of the independent self-contained noise generator units of the invention may be of the form functionally illustrat-ed in Fig. 1, embodying in a single housing, generally designated 29 at 1, a broadband electronic noise source 4 the output of which :'.
,) "
.... .. . . . . .. . .
.. .. :,. ~.. .. -... .. .. - ... - .- ,,,, , . . :. . : -:
i. .. :, i .::, . ,,,~, . : . :. .. , . ., ~
! ` . , . S : ' ' . '. ' . ~ . . . . . . . . , ' ., , ,' . ~ ' ' ... .
" ~''.' ,.' ' ' ' " .'' '., ','' . .;' ;''' ~ ' ' ' ' ' ' . ' ' ' . ' . ' ' " '. ' "'''' '' ' ' ' . . ' ': ~ '; ''" . '' ..
is appropriately frequency-shaped, as before and hereinafter described, in a tunable filter 6-, with the appropriately fre-quency-tailored noise spectrum signal amplitude-adjusted by an attenuator 8 and then amplified at 10 and radiated by a loud-speaker 12. The unit, as previously explained, may be powered at 2, Figs. 1 and 2, from the same power conduits provided for the lighting or other ceiling electric equipment.
mb/~c~D - Sa -'' , ",,, ", , , ,, ,, ,,,, ,, ,,, ,, ,, , ,, , ,, " , , , ,." ,.. .... ... . .. ...
-; . ~.-.. ~,. . .. . . . , ~ , ; . .. , -, . .. . .
As more particularly shown in Fig. 2, the masking generator unit 1 is mountable at variable distances from the main ceiling 3, as by a suspension 5 (which may include the .
power cord 7), or by mounting brac~ets (not shown) connected with conduit junction boxes and the like carried by or from the main ceiling 3. The speaker may point downward or upward, as shown, as desired. Thus control is effected of the position or region of disposition of the unit housing 1 within the .air space between the main ceiling and the sound-transmitting acoustical or other false ceiling surface 3' suspended by struts 5' or otherwise from the main ceiling 3. In this manner, the instal-lation can be effected by the same personnel who install other ceiling structures and from the same power outlets, with flexi-bility for taking advantage of the frequency-tailoring, final-attenuation adjustment and diffusing characteristics of the particular acoustical or other visible ceiling surface 3' or other diffuser at the top of the open space and which serves to transmit the masking noise from the generator units 1 into .
the open space below.
By distributing the plurality of units 1 at appropriate laterally separated positions in the space between the main and f~lse ceiling surfaces 3 and 3', as shown, for example, in Fig. 3, and adjusting the unit heights above the sound-dif-fusing false ceiling surface 3' for appropriate frequency tail-oring or shaping and diffusion, compension can be effected for the frequ~ncy-dependent acoustical power output of the loud-speaker transducer and associated enclosure, for the frequency 28 dependent acoustical noise reduction of the ceiling assembly, and : .
"
~/J~
, - , : - - ~-. .
- 1~4Z1311 for the frequency-dependent contribution of acoustical po~7er from adjacellt generator units 1. ~dditional frequency shaping is employed to limit displacement of the loudspeaker transducer diaphragm at frequencies less than some lower frequency, and for frequencies greater than some higher frequency necessary for effective speech masking, such as of the before-mentioned values. By selecting and/or changin~ appropriate false acoustic ceiling tiles or panels 3', of different porosity or other prop~
erties, or providing metal or other diffuser baffle structures including fluorescent or other light diffusing structures, tail-oring or shaping of diffusion and spreading characteristics can be attained.
In a typical installation of the type shown in Fig. 3, the units 1 were spaced in ro~Js and columns about 12 feet apart, and suspended within a ceiling space (between 3 and 3') about
2 1/2 feet high, with an acoustical suspended ceiling 3' composed of glass fiber and about 2 inches thick. This ceiling 3', to some extent modified the frequency tailoring of the unit filters 6, introducing attenuation adjustment of the order of 3 db for frequencies of the order of 1 KHz, 7 db for frequencies of the order of 3 KHz, and diffusing the sound radiated from the speaker 12 of the unit 1 about 90 compared with the radiation angle of abaut 60 generated by the speaker 12. ~ uniform delocalized cumulative masking noise distribution of substantially the fol-lowing spectrum shaping was effected over an open space of about :
188 square feet: 250 Hz, 47db; 500Hz, 43db; 1 Kl-lz, 37db; 2 KHz, ~;
32db; 4 KHz, 26db; and 8 KHz, 18db.
28 The multiplicity of self-contained electronic generators ~ !~
1 of the invention thus admirably avoids the annoying acoustical .
r~r/~
``` 104Z81~
interference effects caused by phase coherent spatially adjacent radiat~rs Gf the prior art. These effects are particularly ob-jectionable in spaces with little or no acoustically incoherent reverberant field which would be capable of minimizing the spatial pressure variations due to coherent radiators. Since large open plan offices typically employ massive amounts of sound absorbent material in order to provide the maximum amount of attenuation of speech sounds with distance from the talker, with a resulting insignificantly small reverberant field, the coherent radiators of the prior art are consequently particularly subject to these deleterious effects in normal open plan applications, which the present invention thus obviates.
As before indicated, moreover, prior art electronic systems require interconnection of loudspeaker transducers and central generation and amplification equipment via a complex power distribution network, with installation normally accounting for the greater part of total system cost. The self-contained units 1 of the invention, on the other hand, require only con-nection to commonly available AC power in the above-ceiling space.
Failure of a single discrete component in the generator, frequency shaping equipment, power amplifier, or distribution network of a conventional system, moreover, may result in total system failure; whereas failure of an entire self-contained gen-erator 1 of the invention would have minimal effect on total system performance. Small changes in output level or spectrum shape of an individual self-contained generatGr 1 of the invention would also have minimal effect on total system performance; where-28 as the total power and spectral output of a system operated from rwjJ~ - 8 -.,. , . .... , ~ . . . . . . .
1¢1428~
a common generator, as in the prior art is affected to the same degree as the change in generator output. --The unitary nature and constructional and mounting features of the self-contained generators 1, moreover, admirably lends itself to the optional superposition of speech, music or other coherent intelligence signals, as from a transmitter, Fig.
lA, coupling a radio-frequency carrier modulated by such signals to the power lines. A microphone M or music source S may selec-tively be connected, when desired, through an amplifier A to a radio-frequency carrier oscillator-modulator, labelled "RFMod" ~
which is transformer coupled to the power lines. At the unit 1, -Fig. 1, a demodulator or detector DET may similarly optionally be coupled to the power line at T, with the resulting demodulated ~ -intelligence signal superimposed on the noise signals by an adder 4' interposed after the noise source 4.
The present invention thus provides significant im- ;
provement in speech privacy, particularly in open space structures, which can also, however, be attained in varying degrees of effic-acy in other applications of the invention wherein such improve-2~ ments are desired, as in separate partitioned rooms with wall mounting positions. As another example, the background noise with an appropriately tailored frequency spectrum can itself be provided to speaker units by connecting several incoherent sound sources of the type described to the radio-frequency carrier os-- cillator-modulator before described, again transformer-coupled to the power lines as in Fig. 1. Further modifications will also occur to those skilled in this art, and such are considered to fall within the spirit and scope of the invention as defined in the appended claims.
: ' _ g _ rw Jv . . : . - , , . . : : . : . . . - .
188 square feet: 250 Hz, 47db; 500Hz, 43db; 1 Kl-lz, 37db; 2 KHz, ~;
32db; 4 KHz, 26db; and 8 KHz, 18db.
28 The multiplicity of self-contained electronic generators ~ !~
1 of the invention thus admirably avoids the annoying acoustical .
r~r/~
``` 104Z81~
interference effects caused by phase coherent spatially adjacent radiat~rs Gf the prior art. These effects are particularly ob-jectionable in spaces with little or no acoustically incoherent reverberant field which would be capable of minimizing the spatial pressure variations due to coherent radiators. Since large open plan offices typically employ massive amounts of sound absorbent material in order to provide the maximum amount of attenuation of speech sounds with distance from the talker, with a resulting insignificantly small reverberant field, the coherent radiators of the prior art are consequently particularly subject to these deleterious effects in normal open plan applications, which the present invention thus obviates.
As before indicated, moreover, prior art electronic systems require interconnection of loudspeaker transducers and central generation and amplification equipment via a complex power distribution network, with installation normally accounting for the greater part of total system cost. The self-contained units 1 of the invention, on the other hand, require only con-nection to commonly available AC power in the above-ceiling space.
Failure of a single discrete component in the generator, frequency shaping equipment, power amplifier, or distribution network of a conventional system, moreover, may result in total system failure; whereas failure of an entire self-contained gen-erator 1 of the invention would have minimal effect on total system performance. Small changes in output level or spectrum shape of an individual self-contained generatGr 1 of the invention would also have minimal effect on total system performance; where-28 as the total power and spectral output of a system operated from rwjJ~ - 8 -.,. , . .... , ~ . . . . . . .
1¢1428~
a common generator, as in the prior art is affected to the same degree as the change in generator output. --The unitary nature and constructional and mounting features of the self-contained generators 1, moreover, admirably lends itself to the optional superposition of speech, music or other coherent intelligence signals, as from a transmitter, Fig.
lA, coupling a radio-frequency carrier modulated by such signals to the power lines. A microphone M or music source S may selec-tively be connected, when desired, through an amplifier A to a radio-frequency carrier oscillator-modulator, labelled "RFMod" ~
which is transformer coupled to the power lines. At the unit 1, -Fig. 1, a demodulator or detector DET may similarly optionally be coupled to the power line at T, with the resulting demodulated ~ -intelligence signal superimposed on the noise signals by an adder 4' interposed after the noise source 4.
The present invention thus provides significant im- ;
provement in speech privacy, particularly in open space structures, which can also, however, be attained in varying degrees of effic-acy in other applications of the invention wherein such improve-2~ ments are desired, as in separate partitioned rooms with wall mounting positions. As another example, the background noise with an appropriately tailored frequency spectrum can itself be provided to speaker units by connecting several incoherent sound sources of the type described to the radio-frequency carrier os-- cillator-modulator before described, again transformer-coupled to the power lines as in Fig. 1. Further modifications will also occur to those skilled in this art, and such are considered to fall within the spirit and scope of the invention as defined in the appended claims.
: ' _ g _ rw Jv . . : . - , , . . : : . : . . . - .
Claims (11)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process of distributing masking sound in an open-plan space and the like, that comprises, independently and incoherently generating and radiating noise at a plurality of positions laterally separated from one another above a sound-transmitting surface covering such an open space; shaping the frequency spectrum of the noise to correspond substantially to that desired for speech privacy masking; and adjusting the lateral separation of noise radiation positions from one another to control the diffusion and distribution of the masking noise sound cumulatively transmitted through and below said surface into the open space, in order to provide a uniform, de-localized incoherent masking radiation within said open space.
2. A process as claimed in claim 1 and in which intelligence signal radiation is superimposed upon said incoher-ent masking noise radiation.
3. Apparatus for distributing masking noise through a false ceiling surface and the like into an open space there-below, having, in combination, a plurality of independent inco-herent noise-generating units, each provided with a separate electronic noise source, frequency shaping filter, amplifying and sound radiating means; means for mounting said units at a plurality of positions laterally spaced over the ceiling surface;
means for powering said units from ceiling power conduit means;
and means for tuning the shaping filter and for adjusting the height of said units above said ceiling surface and adjusting the lateral separation of said units to provide a predetermined speech privacy noise attenuation spectrum below said ceiling surface, said surface being selected to diffuse the noise ra-diated from the plurality of units to provide cumulative de-localized incoherent masking radiation within said open space.
means for powering said units from ceiling power conduit means;
and means for tuning the shaping filter and for adjusting the height of said units above said ceiling surface and adjusting the lateral separation of said units to provide a predetermined speech privacy noise attenuation spectrum below said ceiling surface, said surface being selected to diffuse the noise ra-diated from the plurality of units to provide cumulative de-localized incoherent masking radiation within said open space.
4. Apparatus as claimed in claim 3 and in which said tuning and adjusting means are adjusted to provide substantially the following relative levels in the open space, measured in octave bands: 125 Hz-Odb; 250 Hz-3db; 500 Hz-6db; 1000 Hz-11db;
2000 Hz-18db; 4000 Hz-26db; 8000 Hz-36db.
2000 Hz-18db; 4000 Hz-26db; 8000 Hz-36db.
5. Apparatus as claimed in claim 3 and in which means is provided for receiving and demodulating radio-frequency carried intelligence signals and adding the same to the incoherent masking noise from said electronic noise source to radiate with the noise from said sound radiating means.
6. Apparatus as claimed in claim 5 and in which means is provided for carrying said intelligence signals along said power conduit means, and said receiving and demodulating means is coupled to said power conduit means.
7. Apparatus for distributing masking noise into an open space, having, in combination, a plurality of independent incoherent noise-generating units, each provided with a separate electronic noise source, frequency shaping filter, amplifying and sound radiating means; means for mounting said units at a plur-ality of positions laterally spaced from one another; means for powering said units from power conduit means associated with said space; and means for tuning the shaping filter and for adjusting the height and the lateral separation of said units to provide a predetermined speech privacy noise attenuation spectrum within said space, and to provide incoherent masking radiation there within.
8. Apparatus as claimed in claim 7 and in which said tuning and adjusting means are adjusted to provide substantially the following relative levels, measured in octave bands: 125 Hz-Odb; 250 Hz-3db; 500 Hz-6db; 1000 Hz-11db; 2000 Hz-18db; 4000 Hz-26db; 8000 Hz-36db.
9. Apparatus as claimed in claim 7 and in which means is provided for receiving and demodulating radio-frequency car-ried intelligence signals and adding the same to the incoherent masking noise from said electronic noise source to radiate with the noise from said sound radiating means.
10. Apparatus as claimed in claim 9 and in which means is provided for carrying said intelligence signals along said power conduit means, and said receiving and demodulating means is coupled to said power conduit means.
11. Apparatus as claimed in claim 3 and in which dif-fusing and frequency-spreading means is provided below said units.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52794174A | 1974-11-29 | 1974-11-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042811A true CA1042811A (en) | 1978-11-21 |
Family
ID=24103596
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA240,268A Expired CA1042811A (en) | 1974-11-29 | 1975-11-24 | Process and apparatus for speech privacy improvement through incoherent masking noise sound generation in open-plan office spaces and the like |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1042811A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7460675B2 (en) | 2004-06-21 | 2008-12-02 | Soft Db Inc. | Auto-adjusting sound masking system and method |
-
1975
- 1975-11-24 CA CA240,268A patent/CA1042811A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7460675B2 (en) | 2004-06-21 | 2008-12-02 | Soft Db Inc. | Auto-adjusting sound masking system and method |
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