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JP2001069590

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DESCRIPTION JP2001069590
[0001]
FIELD OF THE INVENTION The present invention relates generally to the reduction of headset
noise, and more particularly, to a novel and / or passive reduction of noise perceived by the user
of the headset. Devices and techniques.
[0002]
BACKGROUND OF THE INVENTION As background art, US Pat. Nos. 5,305,387, 5,208,868,
5,181,252, 4,989,271 and 4, Nos. 922,542, 4,644,581 and 4,455,675. Further, reference is also
made to Bose Active Noise Reduction Headsets commercially available from Bose Corporation or
in the past. This headset is incorporated in the present application.
[0003]
SUMMARY OF THE INVENTION An important object of the present invention is to improve the
noise reduction for a headset.
[0004]
SUMMARY OF THE INVENTION In accordance with the present invention, an ear cup is provided
which is closed at a position spaced rearward from the user's ear and is open at a position
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adjacent and forward of the user's ear.
There is a driver inside the ear cup. The ear cup has a cushion located in the front opening. The
cushion is an ear opening for receiving the user's ear, and an annular ridge surrounding the ear
opening, having a plurality of openings, the adjacent openings typically being a circle of the ear
opening It is formed to have annular ridges that are spaced from one another by a degree of the
width of the opening measured along the circumference. Each opening is approximately
perpendicular to the circumference of the ear opening and has a radial width slightly smaller
than the radial width of the annular ridge. For active noise reduction, the provided microphone is
adjacent to the driver and is coupled to the driver by means of electronic circuits which provide a
reduction of the active noise and an acoustic load around the microphone and the driver. The
acoustical load consists of air in a resistive mesh screen and / or tube.
[0005]
Other features, objects and advantages will be apparent from the following detailed description
read in conjunction with the accompanying drawings.
[0006]
DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, and in particular to
FIGS. 1A and 1B, a perspective view of an ear cup assembly according to the present invention is
shown.
However, the porous cushion shown in FIG. 1B has been removed. The ear cup 11 is closed at the
back 12 which is the side away from the user's ear. Also, the ear cup 11 is provided in close
proximity to the driver 12 and is typically covered by a resistive mesh screen 13 formed with an
opening 13A exposing the microphone and equipped with an acoustical load The microphone is
supported. Electronic circuitry couples the microphone and driver 12 together, provides active
noise reduction, and is worn by the user for transmission by the driver 13 through the cable 14
In order to convert the audio signal into the desired sound signal, it is further converted by the
microphone into a noise-reduced audio signal.
[0007]
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Referring now to FIG. 1B, a cushion 15 covers the exposed front opening adjacent to the ear of
the wearing user. The cushion 15 has an ear opening 15A for receiving the wearing user's ear,
and an annular ridge 16 surrounding the ear opening 15A formed to have a plurality of openings
such as 16A. Is formed. Through this plurality of openings, when assembly is complete, one can
see the annular ring of foam that remains in contact with the driver 12.
[0008]
Referring to FIG. 2, a cross-sectional view of the entire assembled ear cup is shown. The driver 12
is placed in the ear cup 11, and the driver plate 12A extends rearward from the lip 11A of the
ear cup 11 toward the ridge 11B. The microphone 17 is then in close proximity to the driver 12
and is covered by the wire mesh resistive cover 13. The cushion 15 covers the front opening of
the ear cup 11 and includes a foam 15B.
[0009]
Referring to FIG. 3, a pictorial perspective view of the interior of the ear cup 11 is shown.
However, the cushion 15, the microphone 17 and the wire mesh resistive cover 13 have been
removed and the structural details are illustrated to some extent. The ear cup 11 is formed to
receive an audio signal converted by the driver 12 and to have a cable entry 11 C for receiving a
cable that interconnects the external electronic circuitry and the driver and the microphone. The
driver plate 12A has resistive cover holders 21A and 21B that support the wire mesh resistive
cover 13. A microphone holder 22 extends from the rear wall of the ear cup 11 to support the
microphone 17 and enclose the air that constitutes the acoustic load. The driver plate mounting
bosses 12 B and 12 C provide a means for attaching the driver 12 to the ear cup 11. The driver
12 divides the ear cup 11 into a front volume, typically about 50 cc, adjacent to the front
opening, and a back volume, typically about 15 cc, surrounded by the closed end of the ear cup
11.
[0010]
Referring to FIG. 4, a rear view of the earcup 11 is shown showing the mass port 11C and the
resistive port 11D covered by the wire mesh.
[0011]
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Referring now specifically to FIG. 5, a block diagram is shown illustrating the logical
configuration of a system incorporating the present invention.
This corresponds substantially to FIG. 1 of US Pat. No. 4,644,581 cited above. The signal
combiner 30 algebraically combines the signal desired to be reproduced at the input 24 by the
earphones and the feedback signal provided by the microphone preamplifier 35. The signal
combiner 30 provides the combined signal to the compressor 31, which limits the level of the
high level signal. The output of the compressor 31 is given to a compensator 31A. Compensator
31A includes a compensation circuit that ensures that the open loop gain satisfies the Nyquist
stability criteria, so that the system does not oscillate when the loop is closed. The system shown
is identical for each of the left and right ears.
[0012]
The power amplifier 32 amplifies the signal from the compensator 31A to energize the earphone
driver 17 to provide an acoustic signal in the front cavity. This acoustic signal is combined with
the external noise signal entering the front cavity from the area represented as the acoustic input
terminal 25 to produce a combined acoustic pressure signal represented as circle 36 in the front
cavity, the synthesis The acoustic pressure signal thus generated is given to the microphone 11
and converted. Microphone amplifier 35 amplifies the converted signal and provides it to signal
combiner 30.
[0013]
The structural arrangement of the embodiment of the present invention has been described
above. Next, the principle of operation will be described. The problem with circumaural
headphones that reduce active noise is that earcup resonances produce a rough acoustic
response that is a function (correlated) of the user's head, making electronic compensation
difficult. ing.
[0014]
One approach to smoothing the acoustic response is to place a dampening material, typically a
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highly absorbent foam, around the wall of the ear cup. This approach typically requires a
considerable thickness of foam to provide sufficient damping, and also requires a relatively large
volume in the ear cup to accommodate thick foam. Furthermore, the damping of the highly
absorbent foam is a sensitive function of the variability of the physical size of the foam and
atmospheric conditions, resulting in an inconsistent acoustic response.
[0015]
The resonance in the earcup causes instability by causing oscillation at a certain frequency,
which typically limits the amount of feedback for active noise reduction. By applying an acoustic
load to the microphone and the driver by the wire mesh resistive cover 13 and / or the enclosed
air, the resonance is reduced significantly. Therefore, in a relatively small volume earcup, the
gain of the feedback loop can be increased, and the reduction of active noise is significantly
improved. By forming an opening in the annular ridge 16 of the cushion 15 to expose the foam
material 15B, the effective volume of the ear cup significantly increases to surround that volume
and provide additional damping to provide additional damping. Helps smooth the audio response
and controls stability with the headset away from the head occupied by the cushion 15, thereby
increasing passive damping.
[0016]
The invention has a number of advantages. Although the size of the cup is relatively small, there
is considerable effective volume due to the additional effective volume provided by the cushion
15 accessed through an opening such as 16A. The effects of resonances within the earcup 11 are
significantly reduced by the wire mesh resistive cover 13 and / or the enclosed air, thus allowing
a significant increase in the loop gain of the active noise reduction system.
[0017]
It will be apparent to those skilled in the art that various adaptations, modifications and
variations of the specific devices and techniques disclosed in this application may be made
without departing from the spirit of the present invention. You can do it. Consequently, the
present invention is a novelty of the individual novel features and the multiple features that exist
and possess in the devices and techniques disclosed and limited only by the claims disclosed in
this application. It should be construed to encompass all combinations and combinations.
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[0018]
Brief description of the drawings
[0019]
1 consists of FIG. 1A and FIG. 1B.
FIG. 1A is a perspective view of a headset ear cup assembly that is an embodiment of the present
invention. However, in FIG. 1A, the cushion according to the invention shown in FIG. 1B has been
removed.
[0020]
2 is a cross-sectional view of the ear cup assembly according to the present invention.
[0021]
FIG. 3 is a pictorial perspective view of the interior of the ear cup assembly but with the
microphone and resistive cover plate removed.
[0022]
4 is a perspective view showing the outside of the ear cup.
[0023]
5 is a block diagram of a system embodying the present invention.
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