Note: Descriptions are shown in the official language in which they were submitted.
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MICROPHONE PLACEMENT IN HEARING ASSISTANCE DEVICES
TO PROVIDE CONTROLLED DIRECTIVITY
Claim of Benefit
This application claims the benefit of U.S. Provisional Patent Application
Ser. No. 60/656,795, filed February 25, 2005, and to U.S. Patent Application
Ser. No. 11/276,354 filed February 24, 2006, both of which are hereby
incorporated by reference in their entirety.
Field of Disclosure
The present disclosure relates to hearing assistance devices, and in
particular, to microphone placement in hearing assistance devices for
controlled
directivity.
Background
Hearing aids are one form of hearing assistance devices that are used to
correct for hearing loss. Hearing aids provide amplification of sound in
ranges
of hearing loss; however, simply amplifying sound is not necessarily adequate.
Hearing aids also frequently require special attention to reduction of
feedback
and to placement of one or more microphones for proper hearing.
In one type of hearing aid, the behind-the-ear hearing aid ("BTE"), one
or more microphones are found on the hearing aid enclosure that rests behind
the
ear. Such devices do not have the benefit of the ear's anatomy for reflecting
sound to a focal point, such as at the ear canal. Thus, such devices may
receive
sounds from a different set of angles than which is normally heard. In noisy
environments, the user may have difficulty hearing due to the reception of
noise
generally about the user.
There is a need in the art for a system which will provide controlled
directivity of received sound for hearing assistance devices. Such a system
should provide a controllable region of reception so that the user of a
hearing
assistance device can better discern sources, even in noisy environments.
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Summary
The above-mentioned problems and others not expressly discussed herein
are addressed by the present subject matter and will be understood by reading
and studying this specification.
The present disclosure provides various examples, some of which are
apparatus, including: a hearing assistance device housing; a first directional
microphone having first and second sound ports along a first axis, the first
directional microphone producing a first audio signal; a second directional
microphone having third and fourth sound ports along a second axis, the second
directional microphone producing a second audio signal; and signal processing
electronics for adjustment of phase and magnitude of first audio signal and
the
second audio signal, wherein the first, second, third, and fourth sound ports
extend through the hearing assistance device housing.
In some examples the first directional microphone and the second
directional microphone are aligned such that the first axis and the second
axis are
at an angle greater than zero degrees. In some examples, the first axis and
the
second axis are at 90 degrees. In some examples, an omnidirectional
microphone produces a third signal, and the signal processing electronics
include
adjustment of phase and magnitude of the third audio signal.
Various examples, including, but not limited to, behind-the-ear, on-the-
ear, over-the-ear, and in-the-ear hearing assistance devices are set forth.
Various
realizations, include signal processing electronics using a digital signal
processor, microprocessor are discussed. The directional microphones can have
a variety of cardioid, supercardioid, dipole, and hypercardioid reception
patterns
in various combinations.
In various aspects of the present subject matter an example includes an
apparatus, having: a behind-the-ear hearing aid housing; a first directional
microphone having first and second sound ports along a first axis, the first
directional microphone producing a first audio signal; a second directional
microphone having third and fourth sound ports along a second axis, the second
directional microphone producing a second audio signal; a signal processor
receiving the first audio signal and the second audio signal and adapted to
adjust
phase and amplitude of first audio signal and the second audio signal, and
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produce a summed signal; and a receiver (loudspeaker) to produce an audio
signal based on the summed signal, wherein the first, second, third, and
fourth
sound ports extend through the hearing aid housing and wherein the first axis
and second axis are offset by angle B. Various offsets including ninety
degrees,
and others, and various microphone orientations and offsets in the device are
disclosed.
The present subject matter also includes a method, including: applying an
amplitude A and a phase 0 to a signal from a first directional microphone to
produce a first signal; applying an amplitude C and phase iG to a signal from
a
second directional microphone to produce a second signal, the first
directional
microphone and second directional microphone having axes that intersect at an
angle 0; summing the first signal and the second signal to produce an output
signal; and selecting values of A, C, 0, 0 and 0 to provide a desired
reception
pattern from a combination of signals from the first directional microphone
and
the second directional microphone. In some variations, the method includes
applying an amplitude B and phase a to a sound signal from an omnidirectional
microphone to produce a third signal, and wherein the signal processing
includes
selecting values of B and a to provide the desired reception pattern. In some
variations the suinming includes producing magnitudes of the first signal and
second signal; and adding the magnitudes. In some variations the summing
includes adding the first signal and second signal using a complex addition
process to create a complex sum; and producing a magnitude of the complex
sum.
This Suminary is intended to provide an overview of the subject matter
of the present application and is not intended to be an exclusive or
exhaustive
explanation of the present subject matter. The reader is directed to the
detailed
description to provide further information about the subject matter of the
present
patent application.
Brief Description of the Drawings
FIG. 1 shows a plan view of a behind-the-ear hearing aid including
microphone placements according to one embodiment of the present subject
matter.
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FIG. 2 shows a plan view of a behind-the-ear hearing aid including
microphone placements, according to one embodiment of the present subject
matter.
FIG. 3 shows a plan view of a behind-the-ear hearing aid including
microphone placements, according to one embodiment of the present subject
matter.
FIG. 4 shows a dual directional microphone system, according to one
embodiment of the present subject matter.
FIG. 5 shows a microphone system including two directional
microphones and an omnidirectional microphone, according to one embodiment
of the present subject matter.
FIG. 6 shows a microphone system including a directional microphone
and an omnidirectional microphone, according to one embodiment of the present
subj ect matter.
FIG. 7 is a polar plot showing one example of an angular reception
pattern for a system operating according to one embodiment of the present
subject matter and for a particular group of parameters for that system.
FIG. 8 is a polar plot showing one example of an angular reception
pattern for a system operating according to one embodiment of the present
subject matter and for a particular group of parameters for that system.
Detailed Description
The following detailed description refers to subject matter in the
accompanying drawings which demonstrate some exa.inples of specific aspects
and embodiments in which the present subject matter may be practiced. These
embodiments are described in sufficient detail to enable those skilled in the
art to
practice the present subject matter. References to "an", "one", or "various"
embodiments in this disclosure are not necessarily to the same embodiment, and
such references may contemplate more than one embodiment. The following
detailed description is, therefore, not to be taken in a limiting sense, and
the
scope is defined only by the appended claims, along with the full scope of
legal
equivalents to which such claims are entitled.
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The present subject matter relates to method and apparatus for control of
a maximum angle of reception for hearing assistance devices. The examples
provided demonstrate the subject matter on a behind-the-ear hearing device,
however, it is understood that the principles provided herein can be applied
to a
variety of hearing assistance devices, including over-the-ear, on-the-ear, in-
the-
ear and other devices.
FIG. 1 shows a plan view of a behind-the-ear hearing aid including
microphone placements according to one embodiment of the present subject
matter. In this example, the hearing assistance device 102 is a behind-the-ear
(BTE) device, however, as stated above, the present subject matter can be
applied to a variety of devices. The embodiment shown includes two directional
microphones. Each directional microphone receives sound from a pair of sound
ports. Thus, sound ports 1 and 2 are used by the first directional microphone
and
sound ports 3 and 4 are used by the second directional microphone. In some
embodiments, an omnidirectional microphone (not shown) is added to the
combination. Thus, FIG. 1 shows sound ports 1 and 2 being aligned along a
first
axis 104 and sound ports 3 and 4 aligned with a second axis 105. For
convenience, the zero degree reference 110 in all of the following plan views
will be pointing downward, as shown. This reference is not an absolute
direction
and used only to illustrate various angles and positions of microphone
components and sound reception polar patterns throughout.
In FIG. 1, second axis 105 of sound ports 3 and 4 intersects first axis 104
of sound ports 1 and 2 at 90 degrees. In this embodiment, axis 104 coincides
with the axis bisecting the plan view of the device 102. hi various
embodiments,
the separation of the sound ports and intersection location of the sound port
axes
will not be uniform. T11us, in various embodiments the separation between
sound ports 1 and 2 will be lesser than the separation between sound ports 3
and
4. hz various embodiments the separation between sound ports 1 and 2 will be
greater than the separation between sound ports 3 and 4. In various
embodiments the separation between sound ports 1 and 2 will be equal to the
separation between sound ports 3 and 4. In various embodiments the second
axis will intersect the first axis at a location closer to sound port 1. In
various
embodiments the second axis will intersect the first axis at a location closer
to
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sound port 2. In various embodiments the first axis will intersect the second
axis
at a location closer to sound port 3. In various embodiments, the first axis
will
intersect the second axis at a location closer to sound port 4. Thus, any
number
of orientations of ports 1, 2, 3, and 4, are contemplated providing that the
first
axis and second axis intersect at 90 degrees.
FIG. 2 shows a plan view of a behind-the-ear hearing aid including
microphone placements, according to one embodiment of the present subject
matter.
In this example, the hearing assistance device 202 is a behind-the-ear
(BTE) device, however, as stated above, the present subject matter can be
applied to a variety of devices. The embodiment shown includes two directional
microphones. In some einbodiments, an omnidirectional microphone (not
shown) is added to the combination.
In FIG. 2, second axis 205 of sound ports 3 and 4 intersects first axis 204
of sound ports 1 and 2 at 90 degrees; however, in this embodiment, first axis
204
has been rotated by an acute angle relative to the axis 203 bisecting the plan
view of the device 202. In various embodiments, the separation of the sound
ports and intersection location of the sound port axes will not be uniform.
Thus,
in various embodiments the separation between sound ports 1 and 2 will be
lesser than the separation between sound ports 3 and 4. In various embodiments
the separation between sound ports 1 and 2 will be greater than the separation
between sound ports 3 and 4. In various embodiments the separation between
sound ports 1 and 2 will be equal to the separation between sound ports 3 and
4.
In various embodiments the second axis will intersect the first axis at a
location
closer to sound port 1. In various embodiments the second axis will intersect
the
first axis at a location closer to sound port 2. In various embodiments the
first
axis will intersect the second axis at a location closer to sound port 3. In
various
embodiments, the first axis will intersect the second axis at a location
closer to
sound port 4. Thus, any number of orientations of ports 1, 2, 3, and 4, are
contemplated providing that the first axis and second axis are at 90 degrees
and
the first axis is rotated by an acute angle 0 relative to the bisecting axis
203. The
example shown in FIG. 2 is intended to demonstrate one configuration with a(3
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of 45 degrees; however, it is understood that other values of 0 may be used
without departing from the principles set forth herein.
FIG. 3 shows a plan view of a behind-the-ear hearing aid including
microphone placements, according to one embodiment of the present subject
matter.
In this example, the hearing assistance device 302 is a behind-the-ear
(BTE) device, however, as stated above, the present subject matter can be
applied to a variety of devices. The embodiment shown includes two directional
microphones. In some embodiments, an omnidirectional microphone (not
shown) is added to the combination.
This configuration, in various embodiments, provides for the first axis to
be at an angle from the second axis that is not 90 degrees. Thus, the symbol 0
is
the amount of angle between the first and second axis. Although, as the angle
approaches 0 degrees or 180 degrees, the ports would physically overlap, a
zero
degree or 180 degree embodiment features the directional microphone ports
having parallel axes where the ports are not overlapping. For example, where
the ports are side-by-side. Alternate zero degree or 180 degree embodiments
include, but are not limited to, where the ports are along the same axis, but
displaced in distance from each other.
FIG. 4 shows a dual directional microphone system, according to one
embodiment of the present subject matter. Directional microphone 402 is
mounted on the housing of a hearing assistance device to receive sound from
ports 1 and 2, and directional microphone 404 is mounted similarly to receive
sound from ports 3 and 4. Microphone 402 produces a time varying signal
having both amplitude and phase. Signal processor 406 applies amplitude A and
phase 0 to the time varying signal to produce an output signal. In one
embodiment, the signal processor 406 is filtering. In various embodiments, the
filtering is performed in the frequency domain. In various embodiinents, the
filtering is performed in the time domain.
Microphone 404 produces a time varying signal having both amplitude
and phase. Signal processor 408 applies amplitude C and phase ~ to the time
varying signal to produce an output signal. In one embodiment, the signal
processor 408 is filtering. In various embodiments, the filtering is performed
in
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the frequency domain. In various embodiments, the filtering is performed in
the
time domain. The output signals are summed by summer 410. In various
embodiments additional signal processing is performed on the summed signal.
A receiver (loudspeaker) receives the resulting output and produces audio
signals based on it.
In one embodiment, summer 410 derives the magnitude of each input
signal individually and then does an addition of the resulting magnitudes. In
one
embodiment, summer 410 does a complex addition of the signals and then
derives an overall magnitude of the coinplex sum.
Different forms of directional niicrophones may be employed in various
embodiments. For example, if directional microphones are used, such
microphones can provide cardioid, supercardioid, dipole, or hypercardioid
reception patterns for each individual directional microphone. Various
embodiments include combinations of microphones having similar reception
patterns. Various combinations include microphones having different reception
pattenls. Thus, various combinations of reception patterns can be
accomplished,
and the resulting summations of the reception fields can provide a distinctly
different overall reception pattern for the hearing assistance device.
It is understood that the signal processors 406 and 408 and summer 410
can be implemented in hardware, software, or combinations thereof. In varying
embodiments a processor 412 performs all of the operations. Processor 412, in
various embodiments, is a digital signal processor. In some embodiments,
processor 412 is a microprocessor. Other embodiments exist which do not
depart from the scope of the present teachings.
FIG. 5 shows a microphone system including two directional
microphones and an omnidirectional microphone, according to one embodiment
of the present subject matter. Omnidirectional microphone 501 is mounted on
the housing of a hearing assistance device to receive sound through a port.
Omnidirectional microphone 501 produces a time varying signal having both
amplitude and phase. Signal processor 503 applies amplitude B and phase a to
the time varying signal to produce an output signal. In one embodiment, the
signal processor 503 is filtering. In various embodiments, the filtering is
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performed in the frequency domain. In various embodiments, the filtering is
performed in the time domain. The output is sent to summer 510.
Directional microphone 502 and is mounted on the housing of a hearing
assistance device to receive sound from ports 1 and 2, and directional
microphone 504 is mounted similarly to receive sound from ports 3 and 4.
Microphone 502 produces a time varying signal having both amplitude and
phase. Signal processor 506 applies amplitude A and phase 0 to the time
varyiiig signal to produce an output signal. In one embodiment, the signal
processor 506 is filtering. In various embodiments, the filtering is performed
in
the frequency domain. In various embodiments, the filtering is performed in
the
time domain. Microphone 504 produces a time varying signal having both
amplitude and phase. Signal processor 508 applies amplitude C and phase ~ to
the time varying signal to produce an output signal. In one embodiment, the
signal processor 508 is filtering. In various embodiments, the filtering is
performed in the frequency domain. Iii various embodiments, the filtering is
perfonned in the time domain. The output signals are summed by summer 510.
In various embodiments additional signal processing is performed on the
suinmed signal. A receiver (loudspeaker) receives the resulting output and
produces audio signals based on it.
In one embodiment, summer 510 derives the magnitude of each input
signal individually and then does an addition (or subtraction, wliich implies
that
the signal of one channel is multiplied by -1 before it is sumined with the
other
channel) of the resulting magnitudes. In one embodiment, suininer 510 does a
coinplex addition of the signals and then derives an overall magnitude of the
complex sum.
Different forms of directional microphones may be employed in various
embodiments. For example, if directional microphones are used, such
microphones can provide cardioid, supercardioid, dipole, or hypercardioid
reception patterns for each individual directional microphone. Various
embodiments include combinations of microphones having similar reception
patterns. Various combinations include microphones having different reception
patterns. Thus, various combinations of reception patterns can be
accomplished,
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and the resulting summations of the reception fields can provide a distinctly
different overall reception pattern for the hearing assistance device.
It is understood that the signal processors 503, 506 and 508 and summer
510 can be implemented in hardware, soflware, or combinations thereof. In
varying embodiments a processor 512 performs all of the operations. Processor
512, in various embodiments, is a digital signal processor. In some
embodiments, processor 512 is a microprocessor. Other embodiments exist
which do not depart from the scope of the present teachings.
FIG. 6 shows a microphone systein including a directional microphone
602 and an omnidirectional microphone 601, according to one embodiment of
the present subject matter. In one einbodiment, this configuration is achieved
through signal processing by substantially reducing the gain, turning off, or
ignoring the audio signal of a second directional microphone, such as the
directional signal of a system according to FIG. 5. In varying embodiments,
this
configuration is achieved by dedicated inicrophones 602 and 601 and signal
processor 606 and 603, respectively, feeding signals to summer 610.
It is understood that the signal processors 603 and 606 and summer 610
can be implemented in hardware, software, or combinations thereof. In varying
embodiments a processor 612 performs all of the operations. Processor 612, in
various einbodiments, is a digital signal processor. In some embodiments,
processor 612 is a microprocessor. Other embodiments exist which do not
depart from the scope of the present teachings.
For the embodiments set forth in FIGS. 5 and 6, it is understood that the
placement of the omnidirectional microphone on the housing may vary. In one
embodiment, the omnidirectional microphone resides in the vicinity, or even
shares one, of the directional ports. Different locations on the housing can
employed without departing from the scope of the present subject matter.
FIG. 7 is a polar plot showing one example of angular reception for a
system operating according to one embodiment of the present subject matter and
for a particular group of parameters for that system; namely, a cardioid
directional microphone occupying ports 1 and 2 pointing towards 00 along axis
110, and a dipole directional microphone occupying ports 3 and 4 pointing
along
axis 105. The polar response is obtained by taking the magnitude of the
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sum (amplitude and phase) from each directional microphone. This polar
response is frequency independent, assuming that the cardioid and dipole
responses are frequency independent. For example, to achieve the polar pattern
of FIG. 7, one sets A = C and 0 =~ in the system set forth in FIG. 4. It is
understood that parameter values may be changed to change the reception
pattern. Thus, the system is highly controllable and programinable.
FIG. 8 is a polar plot showing one example of angular reception for a
system operating according to one embodiment of the present subject matter and
for a particular group of parameters for that system; namely, a cardioid
directional microphone occupying ports 1 and 2 pointing towards 0 along axis
110, and a dipole directional microphone occupying ports 3 and 4 pointing
along
axis 105. The polar response is obtained by taking the difference between the
cardioid magnitude and the dipole magnitude. This polar response is frequency
independent, assuming that the cardioid and dipole responses are frequency
independent. For example, to achieve the polar pattern of FIG. 8, one sets A=
C
and 0 =~ in the system set forth in FIG. 4. It is understood that paranleter
values may be changed to change the reception pattern. Thus, the system is
highly controllable and programmable.
The present system controls the reception pattern by adjusting A,B,C, 0,
a, and 0 to produce a desired reception pattern. One way to set these
paraineters is to model the values using computer programs, such as MATLAB.
Other programs and modeling may be performed without departing from the
scope of the present subject matter.
It is understood for the embodiments set forth herein, that the port pairs
can be separated by a number of various distances which are limited primarily
by
available space on the housing. For example, port pair distances 3nun to 26mm
are possible in varying einbodiments. Port spacings can vary between ports 1
and 2 as compared to the spacing of ports 3 and 4. Sound port shapes are shown
as circular in the figures, but other shapes may be employed without departing
from the scope of the present subject matter. For purposes of the discussion
throughout this disclosure, port shapes are demonstrative only and can thus
have
various shapes and surface areas or can be covered with an acoustically
appropriate material so that their features are not visible.
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It is understood that the present subject matter provides a great deal of
flexibility and programmability. In various embodiments, an axis of the
microphones is aligned with an intended direction of reception. In various
einbodiments, an axis of the microphones is offset from an intended direction
of
reception.
In various embodiments, the resulting signal from the foregoing
embodiments is amplified and sent to a receiver (loudspeaker), which produces
an audio version of the resulting signal. An additional processing step can
occur
before amplification if desired. In wireless applications, the resulting
signal can
be transmitted using radio frequency energy. Ot11er uses of the resulting
signal
are possible without departing from the scope of the present subject matter.
Althougli specific embodiments have been illustrated and described
herein, it will be appreciated by those of ordinary skill in the art that any
arrangement which is calculated to achieve the same purpose may be substituted
for the specific einbodiment shown. This application is intended to cover
adaptations or variations of the present subject matter. It is to be
understood that
the above description is intended to be illustrative, and not restrictive.
Combinations of the above embodiments, and other embodiments, will be
apparent to those of skill in the art upon reviewing the above description.
The
scope of the present subject matter should be determined with reference to the
appended claims, along with the full scope of equivalents to which such claims
are entitled.
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