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JP2017521730

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DESCRIPTION JP2017521730
A method and system for attenuating noise comprises corresponding acoustical characteristics of
the emitted sound at an approximated position such that the sound emitted from the one or more
speakers is near the area occupant's ear Identifying a location within the region having acoustical
properties that are substantially similar in degree. A microphone, which may be a virtual
microphone, is disposed at the identified position. The microphone detects sound at the identified
location. In response to the sound detected by the microphone, the one or more speakers emit a
noise cancellation audio signal adapted to attenuate one or more frequencies in the sound
detected by the microphone.
System and method of microphone placement for noise attenuation
[0001]
The present invention relates to systems and methods of microphone placement for noise
attenuation.
[0002]
The present specification relates generally to noise cancellation systems, and more particularly to
noise attenuation or cancellation (generally referred to as noise cancellation) in a particular
environment such as a passenger compartment of a vehicle.
[0003]
All examples and features described below can be combined in any technically possible manner.
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[0004]
In one aspect, a method is provided for attenuating noise.
A method is provided in an area having acoustic characteristics wherein the sound emitted from
the one or more speakers is substantially similar in magnitude to the corresponding acoustic
characteristics of the emitted sound at a location near the occupant's ear of the area Identifying
the location of the
A microphone is placed at the identified position.
In response to the sound detected by the microphone, a noise cancellation audio signal is
generated to attenuate one or more frequencies in the sound detected by the microphone.
[0005]
Embodiments of the method can include one of the following features, or any combination
thereof.
[0006]
The microphone of the method may be a virtual microphone composed of a plurality of
microphones arranged in the area.
The area may be the passenger compartment of the vehicle. The signals produced by the
plurality of microphones may be combined to produce a composite response having acoustical
properties substantially similar to the acoustical properties of the emitted sound at locations near
the occupants of the environment. it can. Additionally, the acoustic characteristics of the sound
emitted by the one or more speakers include phase and magnitude.
[0007]
In addition, acoustic characteristics substantially similar in magnitude to the corresponding
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acoustic characteristics of the sound at locations approximated so that the sound emitted from
the one or more speakers is close to the occupant's ear in the area The step of identifying the
location comprises: calculating a first transfer function of the sound emitted from the one or
more speakers at a location near the area occupant's ear; and spatially from the location near the
ear Calculating a second transfer function of the sound emitted from the one or more speakers at
a second position in the region far apart, and comparing the first transfer function to the second
transfer function And C., if the second transfer function is substantially similar in degree to the
first transfer function, then identifying the second position as a candidate for the identified
position at which to place the microphone.
[0008]
The method is that if the phase component of the second transfer function is within 35 degrees
of the phase component of the first transfer function, and the magnitude component of the
second transfer function is the magnitude component of the first transfer function- It may further
include the step of determining that the second transfer function is substantially similar in
degree to the first transfer function if it is within 8.5 dB or +4.5 dB.
[0009]
In another aspect, the noise cancellation system comprises one or more speakers for emitting
sound, and one or more speakers for emitting the sound emitted by the one or more speakers
disposed in the environment. A microphone disposed in the environment at a location having a
transfer function from one or more speakers to the microphone that is substantially similar in
transfer function to the emitted sound to a position in the occupant's ear Equipped with
[0010]
Embodiments of the system can include one of the following features, or any combination
thereof.
[0011]
The microphone may be a virtual microphone composed of a plurality of microphones disposed
in the environment.
The controller receives signals generated by the plurality of microphones and produces a
composite signal having acoustic characteristics substantially equivalent to the acoustic
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characteristics of the emitted sound at a location near the occupants of the environment These
signals can be combined.
Also, each transfer function can have a magnitude component and a phase component.
[0012]
In addition, the microphone can generate a signal in response to detecting a sound, and the noise
cancellation receives a signal generated by the microphone and responds to this signal to
generate a control device that generates an output signal. It can further include.
In response to the output signal, the one or more speakers can emit a noise cancellation audio
signal designed to attenuate one or more frequencies in the sound detected by the microphone.
[0013]
Furthermore, the transfer function is such that if one phase component of the transfer function is
within 35 degrees of the other phase component of the transfer function, and one magnitude
component of the transfer function is one of the transfer functions If within -8.5 dB or +4.5 dB of
the other magnitude component, the degrees may be substantially similar to one another.
[0014]
The noise cancellation system may further comprise an amplifier for receiving the output signal
generated by the controller, amplifying and sending the amplified output signal to one or more
speakers for emission.
[0015]
In another aspect, a vehicle comprises a passenger compartment and a noise cancellation system
comprising one or more speakers disposed within the passenger compartment.
1One or more speakers emit sound.
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The noise cancellation system is substantially similar in magnitude to the transfer function of the
sound emitted from the one or more speakers to a position in the occupant's room ear from the
one or more speakers. The microphone further comprises a microphone disposed within the
passenger compartment at a location having a transfer function from one or more speakers to
the microphone.
[0016]
Embodiments of the system can include one of the following features, or any combination
thereof.
[0017]
The microphones of the noise cancellation system may be virtual microphones comprised of a
plurality of microphones disposed in the environment.
[0018]
The controller receives signals generated by the plurality of microphones to produce a composite
signal having acoustic characteristics substantially equivalent to the acoustic characteristics of
the emitted sound at a location near the occupants of the environment. Can be combined.
[0019]
The microphone can generate a signal in response to detecting the sound, and the controller can
receive the signal generated by the microphone and generate an output signal in response to the
signal.
In response to the output signal, the one or more speakers can emit a noise cancellation audio
signal adapted to attenuate one or more frequencies in the sound detected by the microphone.
[0020]
Furthermore, each transfer function can have a magnitude component and a phase component.
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Furthermore, if one phase component of the transfer function is within 35 degrees of the other
phase component of the transfer function, and one magnitude component of the transfer
function is the other magnitude of the transfer function When within -8.5 dB or +4.5 dB of the
components, the transfer functions are substantially similar to one another.
An amplifier may receive the output signal generated by the controller, amplify it, and send the
amplified output signal to one or more speakers for emission.
[0021]
The above and other features and advantages can be better understood by reference to the
following description in conjunction with the accompanying drawings in which like numerals
indicate like components and features in the various figures.
The drawings are not necessarily to scale, emphasis instead being placed upon illustrating
features and principles of implementation.
[0022]
FIG. 1 is a diagram of an environment with a noise cancellation system installed in the
environment. FIG. 2 illustrates deployment of a noise cancellation system in an environment to
an occupant. It is a model used to infer candidate positions for microphone placement at a given
ear position relative to a speaker. FIG. 7 is a process flow diagram for reducing noise heard by an
occupant of a particular environment by intentional placement of one or more microphones at
strategic locations in the environment.
[0023]
FIG. 1 shows a generalized example of an environment 10 having a noise cancellation system 12
installed in the environment to attenuate or cancel noise in the environment. The noise
cancellation techniques described herein can be applied to a variety of specific environments,
regardless of whether such environments are open or sealed. For example, deployment of the
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noise cancellation system 12 may be in a vehicle (e.g., car, truck, bus, train, aircraft, boat, and
ship), living room, movie theater, hall. Generally, strategic placement of one or more
microphones, anywhere, can achieve noise cancellation for occupants of such environments, as
described below. For example, in a vehicle, the noise cancellation system 12 may serve to
attenuate low frequency traffic noise, advantageously reducing the need to weight certain areas
of the vehicle for this.
[0024]
In the illustrated example, the noise cancellation system 12 includes one or more speakers 16,
one or more microphones 18, an amplifier 20, and a controller 22. Controller 22 may be
embodied in amplifier 20. 1The strategic placement of the one or more microphones 18 achieves
noise reduction or cancellation at the occupant's ear in the environment 10, as described herein.
Specifically, in a noise cancellation system 12 having a single microphone, the microphones 18
occupy the acoustic transfer function of the sound radiated from the one or more speakers 16 to
the microphone 18 from the one or more speakers 16 It is placed in an environment 10
substantially equal to the acoustic transfer function of the sound to the person's ear. In the
example with multiple speakers, the speakers 16 can be positioned at different distances from
the ear.
[0025]
In general, the acoustic transfer function corresponds to the measured response between the
sound source (e.g. a loudspeaker) and the sound pressure at a given position. The measurement
response measures the relationship between the output (i.e., the sound detected at a given
position) and the input emitted from the source (i.e., the sound). The measured relationship is a
function of frequency and has magnitude and phase components.
[0026]
2
In a noise cancellation system 12 having one or more microphones 18, the microphones 18 are
combined to produce a combined response of the sound emitted by the one or more speakers 16.
The combination of microphones 18 actually operates as a single "virtual" microphone that
produces this combined response. These multiple microphones 18 are strategically placed in the
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environment 10 at a position relative to the one or more speakers 16, so their combined
response is from the one or more speakers 16 to the occupant's ear It has an acoustic transfer
function substantially equal to the acoustic transfer function of sound. Such strategic placement
of the microphones 18 ultimately results in the acoustic transfer function of the sound radiated
from the speakers 16 to the virtual microphone being the acoustic transfer function of the sound
from the one or more speakers 16 to the occupant's ear It results in the strategic placement of a
single virtual microphone that is substantially equal. In the following, references generally
made to microphones generally include, by reference, single "real" microphones and "virtual"
microphones, unless "real" microphones or "virtual" microphones are specifically mentioned.
[0027]
An example of a technique for producing a virtual microphone with a response similar to that of
a real microphone in the occupant's ear is as follows. First, make a virtual microphone from the
transfer function from one or more speakers to the position of the ear, represented by T de (ω),
and one or more speakers, represented by T dsi (ω) A measurement of the transfer function to
the combining microphone is performed, where "i" represents the ith microphone used for the
combination. The error metric (error) is defined as:
[0028]
[0029]
Here, H i (ω) represents a filter applied to the ith microphone.
Then, an optimization algorithm, such as the Levenberg-Marquardt algorithm, can be used to
minimize the error function by adjusting the parameters of the filter H i (ω).
[0030]
1
By placing a microphone whose acoustic characteristics, ie magnitude and phase, of the sound
emanating from one or more speakers substantially match that of the sound in the ear, the
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microphone is far from the ear but the ear It accurately detects what you hear and is in a position
that produces a signal that represents the sound that the occupant has heard. Thus, noise
cancellation directed to sounds detected by the microphone causes corresponding noise
cancellation to occur in the ear.
[0031]
Generally, as illustrated in FIG. 2, one or more speakers 16 are disposed behind the occupant 30
in the environment, for example, mounted on a vehicle headrest, headliner, rear panel or other
interior surface be able to. 1Two real microphones 18 may be disposed on the driver 28
including, for example, one of the one or more speakers 16, and another real microphone 18
(shown in phantom) on the headliner 32. It can be arranged. The amplifier 20 and the control
device 22 can be arranged, for example, in the trunk of a vehicle or in the armrest of a reclining
chair. Controller 22 is in electrical communication with one or more real microphones 18 to
receive the signal produced by each real microphone.
[0032]
1
In response to the signals received from one or more real microphones 18, controller 22
executes an algorithm that generates an output signal. The purpose of the algorithm is to achieve
a significant reduction (eg, at least 4 dB) of noise in the signal. In general, the algorithm
implemented applies one or more filters to the signal produced by each real microphone 18. For
multiple real microphones 18, the algorithm implemented may apply different filters to the signal
produced by each real microphone 18 and combine the results to produce an output signal. The
applied filters may be digital or analog, linear or non-linear.
[0033]
Amplifier 20 receives the output signal from controller 22, amplifies it, and passes the amplified
output signal to one or more speakers 16. In response to the amplified output signal, the one or
more speakers 16 have acoustic characteristics that are substantially opposite (ie, approximately
equal in magnitude and 180 degrees out of phase) of the sound captured by the microphone 18
Produces noise reduction or cancellation noise.
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[0034]
FIG. 3 shows that the transfer function is substantially similar to the transfer function of the
nominal ear position of the sound emitted by one of the one or more speakers 16 at a given
frequency (e.g. 100 Hz) A model 100 is shown that illustrates the principles used to suggest
position. The model 100 includes a speaker driver (or box) 102 that includes a speaker 16. The
diagram of FIG. 3 corresponds to a vertical slice through the speaker driver 102 superimposed
on a three dimensional (3-D) coordinate system with X, Y and Z axes. 3The origin 104 (0, 0, 0) of
the D coordinate system is defined to be in front of the speaker 16. Sound radiates from this
point outwards and propagates towards the nominal ear position 106. In this example, the
nominal ear position 106 is defined to be (0, 20, 0) 20 cm apart on the y-axis from the origin (0,
0, 0) of the coordinate system. The position of the ear 106 is on a 3D contour line 108 produced
by the sound emanating from the speaker 16. The surface contours 108 represent locations of
points having acoustical properties substantially equivalent to the sound reaching the ear. That
is, the acoustic transfer function from the speaker 16 to any given point on this contour line 108
is substantially equal to every point on the contour line 108. Contour lines 108 can be referred
to as isobaric surfaces. More specifically, the loudness and phase of the sound from the speaker
are substantially equal at all points on this contour line 108.
[0035]
Contour line 110 represents the location of another point where the acoustic transfer function
from speaker 16 to any given point on contour line 110 is substantially the same for all points on
contour line 110. In this contour line 110, the acoustic transfer function has a smaller magnitude
difference (eg, -8.5 dB) from the transfer function to contour line 108, a delayed phase difference
(eg, -35 degrees), or both. The locations of the points on the spherical contour line 112 represent
another set of positions where the transfer function of the sound from the speaker is
substantially the same for all points on the contour line 112. This transfer function has a greater
magnitude difference (e.g., +4.5 dB) with the transfer function to a point on the contour line 108,
a lead phase difference (e.g., +35 degrees), or both. Each of these contour lines 110, 112
represents another isobaric ball closer to and farther from the speaker 16, respectively, than the
isobaric ball passing through the position 106 of the ear.
[0036]
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Each contour line 108, 110, and 112 intersects the top of the speaker box 102. In this example,
the contour line 108 intersects with the top of the speaker box 102 at coordinates 114, ie, 10 cm
apart or at (10, 0, 0) from the origin 104 along the X axis. Thus, model 100 has a frequency
response substantially equal to the frequency response that the microphone placed at
coordinates 114 near the front end of speaker box 102 received at nominal ear position 106 at
the modeled frequency (ie, , In magnitude and phase). In another example, the contours 108 may
intersect the vehicle's headrest or headliner to indicate other locations for microphone
placement.
[0037]
The contour lines 110, 112 of the model 100 can suggest boundaries for the placement of the
microphones to produce a frequency response substantially equivalent to that received at the
nominal ear position 106. In the case of virtual microphones, any one or more of the real
microphones 18 should be placed outside the contours 110, 112, provided that their composite
response falls on the contours 110, 112 or between the contours 110, 112. Can.
[0038]
FIG. 4 shows an example of a process 200 for performing noise cancellation near the location of
an occupant's ear having a particular predetermined environment. In the description of process
200, reference is made to the elements of FIG. Process 200 includes setup steps in which
possible locations of the microphone placement are identified and one or more microphones are
placed in the area, and an operational phase in which the noise cancellation system 12 performs
noise cancellation. The setup phase involves approximating the position of the expected
occupant's ear in a particular environment (step 202). 1The one or more speakers 16 emit a
sound having a range of frequencies of interest (ie, the original form of this audio signal is
predetermined). For example, the design of the noise cancellation system 12 can be to attenuate
low frequency noise (5 to 150 Hz), and the audio signal includes frequencies over the desired
frequency range. A transfer function (i.e., its magnitude and phase response) from the one or
more speakers to the estimated ear position is calculated for the range of frequencies in the
emitted sound (step 204).
[0039]
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At step 206, one or more locations within the region are identified as candidate locations for
microphone placement. Each candidate position corresponds to a location in the environment
where the transfer function of the sound emitted by the one or more speakers is substantially
equal to the transfer function calculated for the nominal position of the occupant's ear. The
sound emitted from the one or more speakers 16 may be the same as the sound used to calculate
the transfer function at the approximate ear position to identify each candidate position. The
microphones temporarily disposed at the candidate locations capture the sound from the one or
more speakers 16, produce a signal, and send the signal to a controller or other suitable
electronics. From this signal, controller 22 or other suitable electronics measure the frequency
response and compare it to the calculated frequency response for the estimated ear position.
Those measured frequency responses that satisfy certain criteria when compared to the
frequency response calculated for the position of the ear match (eg, "equal", "substantially equal",
"substantially similar" , "Substantially equal", "equal", "well enough", or "same") and are
considered acceptable candidate locations for microphone placement.
[0040]
For example, one criterion for acceptable match is that the magnitude component of the
frequency response to the candidate microphone position is within +4.5 dB or -8.5 dB of the
magnitude of the frequency response at the estimated ear position. The phase component of the
frequency response for a given microphone position may be within plus or minus 35 degrees of
the phase of the frequency response at the estimated ear position. Another example of an
acceptable match is that the transfer functions at the candidate microphone position and the ear
position are sufficiently similar to one another, thus performing noise cancellation on the sound
captured by the microphone at the candidate position: A noise reduction of at least 4 dB
measured at.
[0041]
One example technique for identifying candidate locations is to perform systematic 3D mapping
of the area near the location of the ear (spaced away, separated or moved from) It is. This
systematic mapping involves the steps of holding the microphone at a specific position in the
area, detecting the sound emitted by the speaker by the microphone, and calculating the
frequency response (i.e. transfer function) to the detected sound. , Comparing the frequency
response for a particular microphone position with the frequency response of the ear position,
and repeating (if desired) for another microphone position. Each measured frequency response is
measured using a structured-light sensor or a time-of-flight sensor (e.g., Microsoft (R), KINECT
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(TM)) The camera or 3D scanning device can be linked to a specific physical location, which was
performed by simultaneously tracking the position of the microphone during measurement.
[0042]
A microphone (virtual or real) is placed at one identified candidate position where the transfer
function substantially matches the transfer function calculated for the position of the ear (step
208). Placement of the (virtual or real) microphone in this position results in a "quiet zone"
around the ear for the range of frequencies of interest.
[0043]
During the operation phase, microphones arranged at one candidate position detect sounds that
may contain frequencies considered to be noise. In response to the sound, the microphone
produces a signal (step 210). In response to the signal from the microphone, controller 22
produces an output signal designed to cancel noise in the sound received by the microphone
when amplified by amplifier 20 and converted to sound by speaker 16 (Step 212).
[0044]
The example systems and methods described above include computer components and computer
implemented steps that will be apparent to those skilled in the art. For example, it will be
appreciated by those skilled in the art that computer implemented steps may be stored as
computer executable instructions on a computer readable medium, such as, for example, floppy
disk, hard disk, optical disk, flash ROM, non-volatile ROM, and RAM. It should be.
[0045]
Further, it should be understood by those skilled in the art that computer executable instructions
may be executed on various processors, such as, for example, microprocessors, digital signal
processors, gate arrays, and the like. For ease of explanation, not every step or element of the
above system and method is described herein as part of a computer system, each step or element
corresponding to a corresponding computer system or software configuration Those skilled in
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the art will recognize that it can have elements. Accordingly, such computer systems and / or
software components are effective by describing their corresponding steps or elements (ie, their
functionality) and are within the scope of the present disclosure.
[0046]
Several implementations have been described. Nevertheless, it will be understood that further
modifications can be made without departing from the scope of the inventive concept described
herein, and thus other embodiments are within the scope of the following claims.
[0047]
10 Environment 12 noise cancellation system 16 one or more speakers 18 one or more
microphones 20 amplifiers 22 controllers 30 occupants 32 headliners 100 models 102 speaker
drivers (or boxes) 104 origin 106 nominal ear position 108 3D Contours, Surface contours 110
Contours 112 Spherical contours 114 Coordinates
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