53`\— k
US005815582A
Ulllted States Patent [19]
[11] Patent Number:
Claybaugh et al.
[45] Date of Patent:
[54]
ACTIVE PLUS SELECTIVE HEADSET
[56]
[75]
Inventors: David Claybaugh, GermantoWn;
References Cited
3,952,158 4/1976 Kyle et a1. .
4,061,875 12/1977 Frei?eld et al. .
Hohman, ToWson, all of Md.
4,064,362 12/1977 Williams .
4,654,871
Assignee: Noise Cancellation Technologies, Inc.,
Linthicum, Md
[21] APPI-NQZ 899,090
[22]
Filed.
.
Jul 23 1997
.
Sep. 29, 1998
U'S' PATENT DOCUMENTS
J e?rey N- Dellellberg, Trumbull;
Ralph Busch, Takoma Park; John
[73]
5,815,582
3/1987 Chaplin ................................... .. 381/72
4,677,678
6/1987 McCutchen .
4,953,217
5,046,103
8/1990 Twiney et al. .
9/1991 Warnaka et 211..
5,091,953
2/1992 Tretter.
5,105,377
4/1992 Ziegler, 11..
5,182,774
1/1993 Bourk ...................................... .. 381/74
,
Primary Examiner—Minsun Oh Harvey
Related US. Application Data
[57]
ABSTRACT
[63]
Commuanon of Sen N0‘ 347’417’ Dec‘ 2’ 1994'
An active plus selective headset system for provision of
[51]
[52]
[58]
Int. Cl.6 ........................... .. A61F 11/06; H03B 29/00
US. Cl. .................................... .. 381/71.6; 381/72
Field of Search .............................. .. 381/72, 74, 103,
active attenuation of broadband noise as Well as speech
?ltering comprising a headset With reference microphones,
residual microphones and speakers on each of a pair of open
381/949, 155, 71,1, 71,6, 71,11, 71,12;
backed muffs and a controller means.
181/206; 379/406, 407, 410, 412, 387,
388, 390, 395
20 Claims, 4 Drawing Sheets
r
4*’
,_,,. ,WLMMWM
5|
.fw
m
a,“
‘I
OPEN
4‘
REFERENCE
,
MICROPHONE
'
SPEAKER
BACK
% HEADSET
SPEAKER
\ 1
\
L454
RESIDUAL MICROPHONES \
53’\—
53
k 55
SPEECH
55
+
RESIDUAL
NOISE
ANTI-NOISE
NOISE
OUTPUT
INPUT
52
\_ 5O
REFERENCE
INPUT
l_
7
_
_
_
—
_
_
'
_
_
_
_
T
—
|
;
IV
.
ADAPTER
63
T
I .
'
I
FEEDBACK
_
_
T
_
_
_
_
W
_
_
_
_
_
_
'
_
_|
|_\_
[65
I
ADAPTIVE
SPEECH
-o
|
|
:
:
COMPENSATION
:
CANCELLATION
.
FILTER "A"
I
i
:
l
l
.
64
FILTER "T"
r
|
I
'
l
I
|
l
I
t
|
I
60
U.S. Patent
Sep. 29, 1998
Sheet 2 of4
5,815,582
OPEN
SPEAKER
REFERENCE
MICROPHONE
~
BACK
=
HEADSET
3
OR
SPEECH
5
NHSO
+
R.
_
NOISE
_I_.r\|
WD_mwPUI
_
ZPENI
REFERENCE
INPUT
W5
.mm
F
EM
N
N0
C
I
A
up
Fw
_A
raw-v
Mun
nIU.
on_
\I
__I
-
_
_
_
_r+\mx
K
a
LUAETE_
E
M
ES
P
W_
u
_
"I.
5
LT
P
SN
RA_
S
r_
NN
6L
_
2AI
M
_y
?n_wR
5I
W.
__"I
6
ADAPTER
ADAPTIVE FEEDFORWARD
FIG.2
56
O
_
M
mm.
|_.
LPTN_El.
RITD_
ITHA
EuTu_5A AE0UWT
5%
Hu5_
_|
17lI|I
O
U.S. Patent
Sep. 29, 1998
Sheet 4 of4
5,815,582
2965081
[email protected]“21Hv43z?%¢mc
S$2.o51E8:7Z6mS
[email protected] :
5,815,582
1
2
FIG. 3 shoWs a more detailed description of the active
ACTIVE PLUS SELECTIVE HEADSET
control system of FIG. 2.
FIG. 4 shoWs a more detailed description of the adaptive
This application is a continuation, of application Ser. No.
08/347,417, ?led Dec. 2, 1994, noW abandoned.
speech ?ltering technique to be used in this headset design.
BACKGROUND OF THE INVENTION
DETAILED DESCRIPTION OF THE
INVENTION
This invention relates to a headset for actively canceling
unWanted noise While selectively alloWing necessary speech
In FIG. 1 there is shoWn an active/passive closed back
to reach the user’s ear.
In the past, attempts to combine the tWo protections, i.e.,
high and loW frequency attenuation, has resulted in not only
the noise being attenuated, but also the speech that the
10
phones 13 to sense any remaining noise near the ear and
reference microphones 14 to send advanced information for
feed forWard approaches and a system controller 20 Which
Wearer needs to hear. Some systems met only limited
success With ?xed or “near-stationary” noise but not With the
other noise of either (a) varying spectral characteristics or
(b) brief duration noises With “spikes”. Examples of such a
system is found in US. Pat. No. 4,025,721, to Graupe et al
and US. Pat. No. 4,185,168 to Graupe et al. Other systems
like that found in US. Pat. No. 4,455,675 to Bose actively
15
attenuate all sounds at loW frequencies and passively attenu
20
The headset shoWn has closed backs 21, 22 for passive
25
30
3300 HZ) passive hearing protection Works extremely Well at
higher frequencies (typically above 1000 HZ) Whereas active
35
protectors are uncomfortable to Wear. This invention pro
40
frequency band. Additionally, adaptive speech ?ltering or
45
ear after cancellation so that the controller can make further
50
adjustments to the anti-noise signal.
Reference microphones 14 are small electret microphones
attached to the outside of the headset at a distance from the
ear canal. These referenced microphones are used to provide
advanced information about the noise. The higher the fre
55
quency of the noise the more advanced information is
needed to effectively cancel the noise.
FIG. 2 shoWs an active plus selective headset system 50
Another object of this invention is the provision of an
open back muff headset With selective ?ltering.
BRIEF DESCRIPTION OF THE DRAWINGS
an open back muff that incorporates active control and
minimum of input-to-output delay as any delay in the
feedback loop sloWs doWn the system adaptation rate.
Residual microphones 13 are typically small electret
microphones mounted on the speaker frame near the ear.
in-Wire control technology separates speech from noise and
These and other objects of this invention Where reference
is had to the accompanying draWings in Which
FIG. 1 shoWs a typical active/passive headset system
incorporating the instant invention.
FIG. 2 shoWs an active plus selective headset system With
Speakers 12 of the headset are large enough to be capable
They must faithfully reproduce the sound that remains at the
passes the speech to the user.
Accordingly it is an object of this invention to provide an
active noise canceling headset With selectivity.
cies (50—700 HZ).
of producing antinoise at the same level as the noise to be
canceled. They have little or no distortion and have a
vides a solution that simultaneously provides the protection
offered by a passive headset in a lightWeight open back
headset While using active adaptive feed forWard control
algorithms that attenuate all sounds in the 20 to 3300 HZ
DVE is highly effective to use in simple noise environ
ments having only a feW harmonics even Where the noise
varies tremendously. It has also been demonstrated to be
very effective doing broadband cancellation at loW frequen
noise cancellation has been shoWn to achieve similar levels
of protection at loWer frequencies (50 to 1000 HZ). Passive,
hoWever, also attenuates speech and Warning signals and the
Least Means Square (LMS) adapter 24 shoWn in FIG. 1 are
Filtered-X versions Which have inherent compensation for
the effects of the feedback delays around the loop. Box “C”
at 25 is the impulse response of active cancellation system.
Feedback compensator 26 and cancellation ?lter 27 com
plete the component portions of the controller.
can employ other algorithms such as that disclosed in the
noise as Well as noise that covers the speech band (300 to
version of its oWn anti-noise signal from the residual signal.
The adaptive feed forWard uses the reference microphone as
its input and is very effective on complicated noise envi
ronments that are broadband and random in character. The
Alternatively, this invention can employ the algorithm dis
closed in US. Pat. No. 5,105,377 to Ziegler Which is also
incorporated herein by reference. In addition this invention
application of Ziegler in US. patent application Ser. No.
07/421 759; Which is hereby incorporated by reference.
In applications for noise canceling headsets, particularly
in industrial environments, attenuation of loW frequency
The system is designed to use various algorithms such as
that of Ziegler in US. Pat. No. 5,105,377 or an adaptive feed
forWard approach. Both these algorithms use a reference
signal as inputs. The digital virtual earth (DVE) algorithm
develops a reference signal by subtracting an equaliZed
The instant invention solves of total attenuation of the
noise and speech, by providing a solution of an active
headset that can employ any of several selective algorithms
such as those disclosed in US. Pat. No. 4,654,871 to
Chaplin, hereby incorporated by reference herein.
synthesiZes the anti-noise signal.
attenuation Without the speakers, microphones and system
controller, this headset Would be a typical passive hearing
protector.
ate all high frequency sounds. These sounds include speech
and Warning signals that Want to be heard by the person
Wearing the headset.
SUMMARY OF THE INVENTION
headset system 10. It consists of a typical passive headset 11,
loudspeakers 12 that drive the anti-noise and residual micro
60
With headset 51 having open backed muff positions 52,
reference microphones 53, speakers 54 and residual micro
phones 55. An earplug (not shoWn) may be substituted for
the open backed muff.
The active /passive system 10 previously described can be
con?gured to actively attenuate all sounds in the frequency
65
band from 20 to 3300 HZ Without the need for a passive muff
or earplug. The approach uses an adaptive feed forWard
adaptive speech ?ltering to alloW speech to pass With the
control algorithm to actively attenuate the damaging noise in
“anti-noise” signal.
this band. In order to accomplish this it is necessary to
5,815,582
3
4
minimize the delays of the digital signal processing system,
Which include delays introduced by the anti-aliasing and
in the active control of noise in ducts using the adaptive
feedforWard controller.
Another technique removes neither the anti-aliasing ?lters
nor the reconstruction ?lters but essentially by-passes the
reconstruction ?lters shoWn in FIG. 3 and the acoustic delay
of the speaker and residual microphone physical system, in
order to effectively attenuate noise at the higher frequencies.
The controller 60 has adapters 61, 62, feedback compen
sation 63, cancellation ?lter 64 and adaptive speech ?lter 65.
Controller 60 uses a parallel adaptive speech ?ltering tech
nique to pass speech to the user. Adaptive speech ?ltering
techniques can be employed to Work With the particular
noisy environment. The active controller attenuates noise in
the band of interest and alloWs speech and Warning signals
delays introduced by these ?lters by inserting an analog
Zero’th order tap. This is achieved by placing an ampli?er
betWeen the output of the incoming gain control and the
output of the reconstruction ?lters shoWn in FIG. 3.
A?nal technique, Which Will be even more effective as the
10
at a rate of 40 kHZ or greater, this eliminates the need for
anti-aliasing and reconstruction ?lters because the cut off
frequency of 20 kHZ is at the limit of the loudspeaker
to pass via the adaptive speech ?ltering path Which incor
porates a Warning signal ?lter as shoWn in FIG. 2. It is
similar to the active/passive system eXcept for the open
speed of microprocessor technology increases, is to sample
response.
We claim:
15
1. An active plus selective headset system Which provides
backed headset design and the addition of a parallel adaptive
active broadband attenuation of noise as Well as adaptive
speech ?ltering path and Warning signal ?lter path as inte
speech ?ltering, said system comprising:
gral parts of the controller. The input to the speech ?lter and
a headset means adapted to be Worn by a user;
reference sensing means on said headset means adapted to
controller are the upstream reference microphones 53.
This reference microphone contains noise and speech.
The speech is ?ltered from the noise and passed With the
“anti-noise” generated from the adaptive feed forWard con
troller and sent to the headset loud speaker. Both speech and
Warning signals, Which are typically above the speech band
and of knoWn frequencies, Will be heard by the user of the
lightWeight and open back headset.
With reference to FIG. 2, the “anti-noise” and speech
output signals are miXed and input to the speakers. This
sense speech and noise signals;
speaker means on said headset means adapted to convey
25
speech signals to a user’s ear; and
controller means adapted to control the speaker means
based on input from the reference sensing means to
provide active broadband attenuation of all random
inband noise as Well as adaptive speech ?ltering so that
only the speech reaches the ear, Wherein said active
broadband attenuation is accomplished Without syn
chroniZation pulses.
combined signal output sample, uk, is given by
2. A system as in claim 1 Wherein said headset means
includes residual microphone means located on said headset
means and including a feedback means connected to said
speaker means.
3. A system as in claim 2 Wherein said feedback means
35
includes an adaptive speech ?lter means and a cancellation
?lter means.
uk is the output speech and anti-noise value
4. A system as in claim 2 Wherein said controller means
Where rk is a vector of the most recent eXamples of the
is run by an adaptive feedforWard algorithm.
residual signal
5. A system as in claim 2 Wherein said headset means
includes an open backed muff.
Zk is a vector of the output of the speech ?lter after it
passed through the impulse response Ck
6. A system as in claim 2 Wherein said reference sensing
Ak is a vector of cancellation ?lter coefficients
yk is the output anti-noise value
Wk is the output speech value.
sk is the vector of compensated inputs.
means is an electret microphone.
45
7. A system as in claim 6 Wherein said headset system
comprises a pair of open backed muffs With the reference
sensing means located on the outside of said muffs.
8. An active plus selective headset system Which provides
Inputs to the controller and speech ?lter are the reference
signal, vk, and residual signal rk that are picked up via the
reference sensor and residual sensor respectively. The adap
tive feedforWard controller generates an “anti-noise”, yk,
active broadband attenuation of noise as Well as speech
?ltering, said system comprising:
a headset means adapted to be Worn by a user, Wherein
and the adaptive speech ?lter generates a clean speech
said headset means includes residual microphone
signal, Wk, that are miXed to form the output signal uk Which
is sent to the speakers. Each ear piece operates indepen
dently With separate reference and residual sensors and
means located on said headset means and including a
actuator.
feedback means connected to said speaker means that
55
reference sensing means on said headset means adapted to
It is essential that the output of the speech ?lter, Wk, be
sense speech, noise and Warning signals;
?ltered through the system in pulse response, Ck, and
speaker means on said headset means adapted to convey
subtracted from the residual input, rk, so as not to interfere
speech and Warning signals to a user’s ear; and
With the operation of the adaptive feedforWard controller.
OtherWise, the controller Will attempt to adapt to and cancel
the speech signal that is output to the speaker.
controller means adapted to control the speaker means
based on input from the reference sensing means to
provide active broadband attenuation of noise as Well
Several techniques can be used to minimiZe the delays of
the system. First, passive material can effectively act as a
loW pass ?lter for the input reference and residual sensors.
This Would eliminate the need for anti-aliasing ?lters and
thus the delays introduced by these ?lters Would be elimi
nated. This technique has been shoWn to be quite effective
includes an adaptive speech ?lter means adapted to
?lter speech from noise and a cancellation ?lter means;
as speech ?ltering so that only the Warning signals and
speech reach the ear.
65
9. An active plus selective headset system Which provides
active broadband attenuation of noise as Well as speech
?ltering, said system comprising:
5,815,582
6
5
a speaker located on an inside portion of said muff; and
a controller attached to said reference microphone such
a headset means adapted to be Worn by a user, Wherein
said headset means includes residual microphone
means located on said headset means and including a
that said signals sensed by said reference micro
feedback means connected to said speaker means that
includes an adaptive speech ?lter means and a cancel
lation ?lter means;
reference sensing means on said headset means adapted to
phone act as an input to said controller; said con
troller producing an anti-noise output at said speaker
to eliminate said unWanted random inband noise
signals at a user’s ear and removing noise from said
sense speech, noise and Warning signals:
speech signal by adaptive speech ?ltering so that the
speech signals output to the user’s ear is clearer,
speaker means on said headset means adapted to convey
speech and Warning signals to a user’s ear; and
10
inband noise signals is accomplished Without syn
controller means adapted to control the speaker means
based on input from the reference sensing means to
provide active broadband attenuation of noise as Well
as speech ?ltering so that only the Warning signals and
speech reach the ear;
Wherein an output from said adaptive speech ?ltering
chroniZation pulses.
14. A headset system as in claim 13, further comprising a
15
output can be adjusted to compensate for said unWanted
random inband noise.
means is miXed With an output from said controller
15. A headset system as in claim 13 Wherein said con
troller includes a feedback compensator connected to said
means.
10. An active plus selective headset system Which pro
vides active broadband attenuation of noise as Well as
speaker.
speech ?ltering, said system comprising;
16. A headset system for providing active broadband
attenuation of unWanted noise, as Well as speech ?ltering,
a headset means adapted to be Worn by a user, Wherein
25
means located on said headset means and including a
comprising:
a pair of muffs, each of said muffs comprising:
feedback means connected to said speaker means that
includes an adaptive speech ?lter means and a cancel
lation ?lter means;
reference sensing means on said headset means adapted to
a reference microphone attached to an outside portion
of said muff for sensing speech signals, Warning
signals, and unWanted noise signals;
a speaker located on an inside portion of said muff; and
sense speech, noise and Warning signals;
a controller including a feedback compensator con
speaker means on said headset means adapted to convey
nected to said speaker and attached to said reference
speech and Warning signals to a user’s ear; and
controller means adapted to control the speaker means
based on input from the reference sensing means to
provide active broadband attenuation of noise as Well
residual microphone attached to said speaker for sensing any
unWanted random inband noise near the user’s ear and
providing an output to said controller so that the anti-noise
means and a resulting signal passed to said speaker
said headset means includes residual microphone
Wherein said elimination of said unWanted random
microphone such that said signals sensed by said
35
reference microphone act as an input to said con
troller; said controller producing an anti-noise output
at said speaker to eliminate said unWanted noise
as speech ?ltering so that only the Warning signals and
speech reach the ear,
Wherein an output from said adaptive speech ?ltering
signal at a user’s ear and removing noise from said
speech signal so that the speech signals output to the
user’s ear is clearer.
means is ?ltered by an impulse response of the can
cellation means and subtracted from a signal from the
residual microphone so as not to interfere With opera
tion of said controller means.
Wherein said feedback compensator includes an adaptive
speech ?lter and a cancellation ?lter.
17. A headset system as in claim 13 Wherein said con
feedforWard method of noise cancellation.
12. A system as in claim 2 Wherein said residual micro
phone means is internal of said speaker means on said
troller is operated based on an adaptive feedforWard algo
rithm.
18. A headset system as in claim 13 Wherein said refer
ence sensing microphone is an electret microphone.
19. A system as in claim 1 Wherein the reference sensing
means is adapted to additionally sense Warning signals, the
headset means and said controller means is adapted to
speaker means is adapted to convey speech and Warning
employ a feedback method of noise cancellation.
signals to the user, and the controller means is adapted to
provide active broadband attenuation of noise as Well as
11. Asystem as in claim 1 Wherein said reference sensing
means is external of said speaker means on said headset
means and said controller means is adapted to employ a
13. A headset system for providing active broadband
attenuation of unWanted random inband noise, as Well as
adaptive speech ?ltering, comprising:
a pair of muffs, each of said muffs comprising:
a reference microphone attached to an outside portion
of said muff for sensing speech signals and unWanted
random inband noise signals;
45
speech ?ltering so that only the Warning signals and speech
55 reach the ear.
20. Aheadset system as in claim 13, Wherein the reference
microphone additional senses Warning signals.
*
*
*
*
*
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement