Headset noise reducing

Information

  • Patent Grant
  • 6597792
  • Patent Number
    6,597,792
  • Date Filed
    Thursday, July 15, 1999
    25 years ago
  • Date Issued
    Tuesday, July 22, 2003
    21 years ago
Abstract
A headset has an earcup with front opening adjacent to an annular cushion formed with a plurality of openings facing the inside of the earcup that acoustically couples the earcup volume to the cushion volume. A driver is seated inside the earcup with a microphone adjacent to the driver. Active noise reducing circuitry intercouples the driver and microphone. An acoustic load that may comprise a wire mesh resistive cover and/or air mass adjacent the microphone is constructed and arranged to reduce the effect of resonances in the earcup volume.
Description




The present invention relates in general to headset noise reducing and more particularly concerns novel apparatus and techniques for actively and/or passively reducing the noise perceived by the user of a headset.




BACKGROUND OF THE INVENTION




For background reference is made to U.S. Pat. Nos. 5,305,387, 5,208,868, 5,181,252, 4,989,271, 4,922,542, 4,644,581 and 4,455,675. Reference is also made to the Bose active noise-reducing headsets that are or were commercially available from Bose Corporation that are incorporated by reference herein.




It is an important object of the invention to provide improved noise-reducing for headsets.




BRIEF SUMMARY OF THE INVENTION




According to the invention, there is an earcup closed at the back away from the ear of a user and open at the front adjacent to the ear of the user. There is a driver inside the earcup. The earcup has a cushion that is seated in the front opening and formed with an ear opening for accommodating the ear of the user and an annular ridge surrounding the ear opening formed with a plurality of openings with adjacent openings typically spaced from each other by of the order of the width of an opening measured along the circumference of the ear opening with each opening having a radial width generally perpendicular to the circumference of the ear opening slightly less than the radial width of the annular ridge. For active noise reduction, there is a microphone adjacent to the driver coupled to the driver by electronic circuitry that furnishes active noise reduction and an acoustical load around the microphone and driver. The acoustic load may comprise a resistive mesh screen and/or air in a tube. Other features, objects and advantages will become apparent from the following detailed description when read in connection with the accompanying drawings in which:











BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING





FIG. 1A

is a perspective view of a headset earcup assembly embodying the invention with the cushion shown in

FIG. 1B

according to the invention removed;





FIG. 2

is a sectional view of an earcup assembly according to the invention;





FIG. 3

is a pictorial perspective view into the earcup assembly with the microphone and resistive cover plate removed;





FIG. 4

is a perspective view showing the outside of an earcup; and





FIG. 5

is a block diagram of a system embodying the invention.











DETAILED DESCRIPTION




With reference now to the drawings and, more particularly,

FIGS. 1A and 1B

thereof, there is shown a perspective view of an earcup assembly according to the invention with the perforated cushion of

FIG. 1B

removed. Earcup


11


is closed at the rear away from the ear of a user and supports driver


12


and a closely adjacent microphone (not seen in

FIG. 1A

) that is covered by resistive mesh screen


13


typically formed with an opening


13


A exposing the microphone and comprising an acoustical load. Electronic circuitry intercouples the microphone and driver


12


to provide active noise reduction and exchange audio signals through cable


14


for transduction by driver


12


into desired sound signal for the wearing user and by the microphone into a noise-reducing audio signal.




Referring also to

FIG. 1B

, cushion


15


covers the exposed front opening adjacent to the ear of the wearing user and is formed with an ear opening


15


A for accommodating the ear of the wearing user and an annular ridge


16


surrounding ear opening


15


A that is formed with a plurality of openings, such as


16


A, through which an annular ring of foam is visible that rests against driver


12


when assembled.




Referring to

FIG. 2

, there is shown a diagrammatic sectional view through an assembled earcup. Driver


12


is seated in earcup


11


with driver plate


12


A extending rearward from a lip


11


A of earcup


11


to a ridge


11


B with microphone


17


closely adjacent to driver


12


and covered by wire mesh resistive cover


13


. Cushion


15


covers the front opening of earcup


11


and includes foam


15


B.




Referring to

FIG. 3

, there is shown a pictorial perspective view into earcup


11


with cushion


15


, microphone


17


and wire mesh resistive cover


13


removed to illustrate certain structural details. Earcup


11


is formed with a cable entry


11


C for accommodating cable


14


for receiving audio signals for transduction by driver


12


and intercoupling external electronic circuitry with the drive and microphone. Driver plate


12


A carries resistive cover holders


21


A and


21


B for supporting the wire mesh resistive cover


13


. Microphone holder


22


extends from the rear wall of earcup


11


for supporting microphone


17


and encloses air that comprises acoustical loading. Driver plate mounting bosses


12


B and


12


C furnish a means for attaching driver plate


12


A to earcup


11


. Driver


12


divides earcup


11


into a front volume typically about 50 CC adjacent to the front opening and a rear volume typically about 15 CC enclosed by the closed end of earcup


11


.




Referring to

FIG. 4

, there is shown a rear view of earcup


11


showing mass port


11


C and resistive port


11


D covered by a wire mesh.




With reference now to the drawing and more particularly

FIG. 5

thereof, there is shown a block diagram illustrating the logical arrangement of a system incorporating the invention corresponding substantially to

FIG. 1

of the aforesaid '581 patent. A signal combiner


30


algebraically combines the signal desired to be reproduced by the earphone on input terminal


24


with a feedback signal provided by microphone preamplifier


35


. Signal combiner


30


provides the combined signal to compressor


31


which limits the level of the high level signals. The output of compressor


31


is applied to compensator


31


A. Compensator


31


A includes compensation circuits to insure that the open loop gain meets the Nyquist stability criteria, so that the system will not oscillate when the loop is closed. The system shown is duplicated once each for the left and right ears.




Power amplifier


31


amplifies the signal from compensator


31


A and energizes earphone driver


2


to provide an acoustical signal in the front cavity that is combined with an outside noise signal that enters the front cavity from a region represented as acoustical input terminal


25


to produce a combined acoustic pressure signal in the front cavity represented as a circle


36


to provide a combined acoustic pressure signal applied to and transduced by microphone


7


. Microphone amplifier


35


amplifies the transduced signal and delivers it to signal combiner


30


.




Having described the structural arrangement of an embodiment of the invention, principles of operation will be described. A problem in active noise-reducing circumaural headphones arises from earcup resonances causing a rough acoustic response that is a function of the head of the user, making electronic compensation difficult.




One approach for smoothing the acoustic response is to place damping material, typically highly absorptive foam, around the walls of the earcup. This approach typically requires a significant thickness of foam to provide sufficient damping and requires earcups of relatively large volume to accommodate the thick foam. Furthermore, the damping of the highly absorptive foam is a sensitive function of the physical dimensions of the foam and atmospheric conditions, causing inconsistent acoustical response.




Resonance in the earcup may produce instability by causing oscillation at certain frequencies that typically limits the amount of feedback for active noise reduction. By acoustically loading the microphone and driver with the wire mesh resistive cover


13


and/or the enclosed air, resonances are significantly reduced, allowing increased gain in the feedback loop and significantly improved active noise reduction in an earcup of relatively small volume.




By forming openings in annular ridge


16


of cushion


15


to expose foam material


15


B, the effective volume of the earcup is significantly increased to embrace the volume occupied by cushion


15


and thereby increase passive attenuation and provides additional damping to help smooth the audio response at the ear and control stability with the headset off the head.




The invention has a number of advantages. Cup size is relatively small, yet there is considerable effective volume with the additional effective volume afforded by cushion


15


accessed through openings such as


16


A. The effect of resonances inside earcup


11


is significantly reduced with wire mesh resistive cover


13


and/or the enclosed air, thereby allowing a significant increase in loop gain of the active noise reducing system.




It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific apparatus and techniques herein disclosed without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims.



Claims
  • 1. A headset comprising,an earcup having a front opening adapted to be adjacent to the ear of the user, a driver inside said earcup, a cushion around the periphery of said front opening formed with an ear opening constructed and arranged to accommodate the ear of a user and formed with a plurality of openings around said opening constructed and arranged to acoustically add the volume of said cushion to the volume of said earcup and enhance passive attenuation.
  • 2. A headset in accordance with claim 1 and further comprising,a microphone inside said earcup adjacent to said driver, and active noise reducing circuitry intercoupling said microphone and said driver constructed and arranged to provide active noise reduction, whereby said cushion with said plurality of openings is further constructed and arranged to furnish additional damping to help smooth the audio response at the ear of a user and control stability with the headset off the head.
  • 3. A headset in accordance with claim 2 and further comprising,an acoustic load in close proximity to said microphone constructed and arranged to reduce the effects of resonances in said earcup.
  • 4. A headset in accordance with claim 3 wherein said acoustic load comprises a wire mesh resistive cover.
  • 5. A headset in accordance with claim 4 wherein said wire mesh resistive cover is formed with an opening near said microphone.
  • 6. A headset in accordance with claim 4 wherein said wire mesh resistive cover coacts with said driver to substantially enclose said microphone.
US Referenced Citations (3)
Number Name Date Kind
4644581 Sapiejewski Feb 1987 A
5182774 Bourk Jan 1993 A
5208868 Sapiejewski May 1993 A
Foreign Referenced Citations (3)
Number Date Country
0582404 Feb 1994 EP
0688143 Dec 1995 EP
0873040 Oct 1998 EP