Note: Descriptions are shown in the official language in which they were submitted.
CA 02592686 2007-06-29
METHOD AND APPARATUS FOR A BINAURAL HEARING ASSISTANCE
SYSTEM USING MONAURAL AUDIO SIGNALS
Field of the Invention
This application relates generally to method and apparatus for a hearing
assistance system, and more particularly to method and apparatus for a
binaural
hearing assistance system using a monaural audio signal.
Background
Modern wireless audio devices frequently apply a monaural signal to a
single ear. For example, devices such as cell phones and cellular headsets
receive
monaural communications for application to a single ear. By this approach,
many
advantages of binaural hearing are lost. Such devices only apply sound to one
ear,
so hearing can be impaired by loud noises in the other ear, and hearing can be
impaired by hearing limitations associated with a particular ear.
Thus, there is a need in the art for an improved hearing assistance system
which provides the advantages of binaural hearing for listening to a monaural
signal. The system should be controllable to provide better hearing,
convenience,
and an unobtrusive design. In certain variations, the system may also allow a
user
to customize his or her hearing experience by controlling the sounds received
by the
system.
Summary
This application addresses the foregoing need in the art and other needs not
discussed herein. The various embodiments described herein relate to a
wireless
system for binaural hearing assistance devices.
One embodiment includes an apparatus for a user having a first ear and a
second ear, including a wireless device to transmit a signal containing
monaural
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information; a first hearing assistance device including: a first radio
receiver to
receive the signal; an adjustable phase shifter adapted to apply a plurality
of
controllable, incremental phase shifts to the monaural information on the
signal; and
a first speaker to produce a first audio signal for the first ear; and a
second hearing
assistance device including a second radio receiver and a second speaker to
produce
a second audio signal for the second ear, wherein the first and second audio
signals
are produced with adjustable relative phase based on a setting of the
adjustable
phase shifter. Various embodiments provide adjustable level controls and
microphones in combinations of first and/or second hearing assistance devices.
Some applications include communications between cellular devices, such as
cellular phones and hearing aids. Various embodiments provide applications
using
wireless audio controllers having packetized audio. Both manual and automatic
adjustments are provided. In various embodiments, different combinations of
receivers and sensors, such as magnetic field sensors, are provided. In
various
embodiments, processing adapted to account for head-related transfer functions
and
for controlling the electronics using it are provided.
In one embodiment, a system is provided for a user having a first ear and a
second ear, including: a device comprising a controllable phase shifter
adapted to
receive a monaural information signal and convert it into a first monaural
signal and
a second monaural signal, the first and second monaural signals having an
interaural
phase shift; a first hearing assistance device including: a first receiver
adapted to
receive the first monaural signal; and a first speaker to produce a first
audio signal
for the first ear; and a second hearing assistance device including: a second
receiver
adapted to receive the second monaural signal; and a second speaker to produce
a
second audio signal for the second ear. Various embodiments provide adjustable
level controls and microphones in combinations of first and/or second hearing
assistance devices. Some applications include communications between cellular
devices, such as cellular phones and hearing aids. Various embodiments provide
applications using wireless audio controllers having packetized audio. Both
manual
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and automatic adjustments are provided. In various embodiments, different
combinations of receivers and sensors, such as magnetic field sensors, are
provided.
In various embodiments, processing adapted to account for head-related
transfer
functions and for controlling the electronics using it are provided.
Methods are also provided, including for example, a method for providing
sound to a first ear and a second ear of a wearer of first and second hearing
assistance devices, including: receiving a monaural information signal;
converting
the monaural information signal into a first monaural signal and a second
monaural
signal, the first and second monaural signals differing in relative phase
which is
controllable; and providing a first sound based on the first monaural signal
to the
first ear of the wearer and a second sound based on the second monaural signal
to
the second ear of the wearer to provide binaural sound to the wearer.
Different
applications, including different methods for laterializing perceived sounds
and
levels of perceived sounds, are provided. Different embodiments for methods of
use, including sensing telephone (telecoil) modes, are provided. Different
embodiments for applications employing head-related transfer functions and
relaying are also provided. A variety of different interaural delays and phase
changes are provided. Other embodiments not expressly mentioned in this
Summary are found in the detailed description.
This Summary is an overview of some of the teachings of the present
application and not intended to be an exclusive or exhaustive treatment of the
present subject matter. Further details about the present subject matter are
found in
the detailed description and appended claims. 1
Brief Description of the Drawings
Various embodiments are illustrated by way of example in the figures of the
accompanying drawings.
FIG. lA shows one system using devices in a direct communication mode
according to one embodiment of the present subject matter.
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FIG. 1 B shows a block diagram of signal flow in a hearing assistance device
according to one embodiment of the present subject matter.
FIG. 1 C shows detail of the signal processing block of FIG. 1 B according to
one embodiment of the present subject matter.
FIG. 2 shows one system of devices in a relaying communication mode
according to one embodiment of the present subject matter.
FIG. 3 shows one system of devices in a relaying communication mode
according to one embodiment of the present subject matter.
FIG. 4A shows one system providing multiple signals according to one
embodiment of the present subject matter.
FIG. 4B shows a signal flow of a wireless audio controller according to one
embodiment of the present subject matter.
Detailed Description
In the following description, for purposes of explanation, numerous specific
details are set forth in order to provide a thorough understanding of the
various
embodiments. It will be apparent, however, to one skilled in the art that the
various
embodiments may be practiced without some of these specific details. The
following description and drawings provide examples for illustration, and are
not
intended to provide an exhaustive treatment of all possible implementations.
It should be noted that references to "an", "one", or "various" embodiments
in this disclosure are not necessarily to the same embodiment, and such
references
contemplate more than one embodiment.
The present subject matter presents sound to both ears of a user wearing
wireless hearing assistance devices which is derived from a single monaural
signal.
Among other things, it allows for better control of the received sound and
obtains
benefits of binaural hearing for listening to the monaural signal. In various
embodiments, the sound presented to one ear is phase shifted relative to the
sound
presented to the other ear. In various embodiments, the phase shift arises
from a
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constant time delay. In various embodiments, the phase shift arises from a
constant
phase shift at all frequencies. In various embodiments, the phase shift arises
from a
phase shift that is varying as a function of frequency. In various
embodiments, the
sound presented to one ear is set to a different level relative to the sound
presented
to the other ear. In various embodiments, the sound presented to one ear is
controllable in relative phase and in relative level with respect to the sound
presented to the other ear. Various apparatus and method set forth herein can
be
employed to accomplish these embodiments and their equivalents. Other
variations
not expressly set forth herein exist which are within the scope of the present
subject
matter. Thus, the examples provided herein demonstrate various aspects of the
present subject matter and are not intended to be limiting or exclusive.
FIG. 1 A shows one system using devices in a direct communication mode
according to one embodiment of the present subject matter. In various
embodiments, wireless device 102 supports one or more communication protocols.
In various embodiments, communications of far field signals are supported.
Some
embodiments employ 2.4 GHz communications. In various embodiments the
wireless communications can include standard or nonstandard communications.
Some examples of standard wireless communications include, but are not limited
to,
FM, AM, SSB, BLUETOOTHTM, IEEE 802.11(wireless LANs) wi-fi,
802.15(WPANs), 802.16(WiMAX), 802.20, and cellular protocols including, but
not limited to CDMA and GSM, ZigBee, and ultra-wideband (UWB) technologies.
Such protocols support radio frequency communications and some support
infrared
communications. It is possible that other forms of wireless communications can
be
used such as ultrasonic, optical, and others. It is understood that the
standards
which can be used include past and present standards. It is also contemplated
that
future versions of these standards and new future standards may be employed
without departing from the scope of the present subject matter.
Such wireless devices 102 include, but are not limited to, cellular
telephones,
personal digital assistants, personal computers, streaming audio devices, wide
area
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network devices, local area network devices, personal area network devices,
and
remote microphones. In various embodiments, the wireless device 102 includes
one
or more of the interface embodiments demonstrated in U.S. Provisional Patent
Application Ser. No. 60/687,707, filed June 5, 2005, entitled: COMMUNICATION
SYSTEM FOR WIRELESS AUDIO DEVICES, and U.S. Patent Application Ser.
No. 11/447,617, filed June 5, 2006, entitled: COMMUNICATION SYSTEM FOR
WIRELESS AUDIO DEVICES which claims the benefit of the provisional
application, the entire disclosures of which are hereby incorporated by
reference.
This is also applicable to wireless devices 202, 302, and 402 as described
herein.
In the embodiment demonstrated by FIG. lA, the listener has primary and
secondary wireless hearing assistance devices Rl and R2. The wireless hearing
assistance devices include, but are not limited to, various embodiments of
hearing
aids. In one embodiment, at least one wireless hearing assistance device is a
behind-the-ear hearing aid. In one embodiment, at least one wireless hearing
assistance device is an in-the-ear hearing aid. In one embodiment, at least
one
wireless hearing assistance device is a completely-in-the-canal hearing aid.
In one
embodiment, at least one wireless hearing assistance device is a wireless
earpiece.
In one embodiment, at least one wireless hearing assistance device is a behind-
the-
ear hearing aid with a wireless adaptor attached. Various examples of wireless
adapters for some hearing assistance devices using a direct-audio input (DAI)
interface are demonstrated in U.S. Patent Application Ser. No. 11/207,591,
filed
Aug. 18, 2005, entitled "WIRELESS COMMUNICATIONS ADAPTER FOR A
HEARING ASSISTANCE DEVICE;" and PCT Patent Application No.
PCT/US2005/029971, filed Aug. 18, 2005, entitled "WIRELESS
COMMUNICATIONS ADAPTER FOR A HEARING ASSISTANCE DEVICE,"
the entire disclosures of which are incorporated by reference.
In the system of FIG. 1 A, the communication protocol of wireless device
102 is adapted to controllably provide wireless communications 105, 109 to
both the
primary wireless hearing assistance device Rl and the secondary wireless
hearing
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assistance device R2. In various embodiments, the communications are
unidirectional. In various embodiments, the communications are bidirectional.
In
various embodiments, the comrnunications include at least one unidirectional
communication and one bidirectional communication. Thus, the system is highly
programmable to adapt to a number of communication requirements and
applications. The system is adapted to provide binaural information to both Rl
and
R2 based a monaural signal from wireless device 102.
In embodiments using BLUETOOTH as the communication protocol, it is
noted that BLUETOOTH is normally directed for point-to-point communications
using PINs (personal identification numbers), such that the wireless device
102. is
typically paired with only one other device, such as primary device Rl. Thus,
to
allow the wireless device 102 to also communicate with secondary device R2, a
second pairing must be done, whether by standard or nonstandard means.
FIG. 1B shows a block diagram of signal flow in a hearing assistance device
according to one embodiment of the present subject matter. For purposes of
demonstration, this block diagram will be that of wireless audio device Ri.
However, it is understood that R2 or any other wireless audio device receiving
the
monaural signal from wireless device 102 could employ the subject matter of
FIG.
1B without departing from the scope of the present subject matter.
The monaural signal 105 is received by receiver 122 which demodulates the
signal and provides the audio signal 128 to signal processor 124. Signal
processor
124 processes the signal to provide signal 130, which is then sent to speaker
126 to
play the processed signal 130 to one ear of a wearer of R1. Various inputs
from a
user or from other external programming means may be employed to provide
control to the signal processing performed by signal processor 124. These
inputs
can be accomplished with a variety of switches, and or programming ports, as
needed to provide signal processing selections and/or parameters for the
system.
In one embodiment, signal processor 124 is a digital signal processor. In
one embodiment, signal processor 124 comprises hardware and software to
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accomplish the signal processing task. In one embodiment, signal processor 124
employs dedicated hardware in combination with other computational or digital
signal processing hardware to perform the signal processing task. It is
understood
that a separate amplifier may be used for amplifying the signa1130 before
sending it
to speaker 126 as is known in the art. Thus, FIG. 1B is intended to
demonstrate the
basic operational blocks at one level and is not intended to be exclusive or
exhaustive of the expressions of the present subject matter.
FIG. 1C shows detail of the signal processing block 124 of FIG. 1B
according to one embodiment of the present subject matter. In this example,
the
monaural input signal 128 is processed by phase shifter 132 to provide a phase
shifted version of the input signal 128. In various embodiments, the phase
shift
arises from a constant time delay applied to input signal 128. In various
embodiments, the phase shift arises from a constant phase shift at all
frequencies
applied to input signa1128. In various embodiments, the phase shift arises
from a
phase shift that is varying as a function of frequency. Thus, control 138
provides
some form of setting for adjusting phase shift and/or for selecting the type
of phase
shift to be applied. In one embodiment, the signal 125 is provided by a source
external to the hearing assistance device RI to control the phase shift.
Various
means for supplying signal 125 include one or more of switches operable by the
user, soft switches programmed by a programming device attached to the hearing
assistance device, or any combination of such inputs. Furthermore, in various
embodiments, signal 125 may be internally generated by systems within the
programming device to provide phase shift control as a function of one or more
of
sound received, conditions detected, and other processes requiring a change of
either phase shift amount and/or mode. The signal 125 may also be transmitted
and
received by the device to adjust its operation.
For example, signa1125 could be generated as a result of a telephone device
in proximity to the hearing assistance device to lateralize received sounds to
the ear
proximal the telephone. As another example, signal 125 can be generated to
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discontinue phase adjustment when the user receives a wireless signal
indicating a
ringing telephone. As another example, signal 125 can be generated to
discontinue
phase adjustment when detecting an emergency vehicle or other siren in
proximity.
Many other applications and operations of the system are possible without
departing
from the scope of the present subject matter. Those provided herein are
intended to
be demonstrative and not exhaustive or limiting of the present subject matter.
FIG. 1 C also shows the phase shifted signal may optionally be processed for
other effects by processor 134. The resulting signal is sent to amplifier
circuit 136
to generate output 130 for speaker 126. Processor 134 allows.further
adjustment of
the signal, including level adjustment. For example, the level and phase of
the
signal 130 can be programmably controlled, in one embodiment. If the hearing
assistance device on the other ear (e.g., R2) does not adjust phase or level,
then by
controlling Rl a wearer of the hearing assistance devices Rl and R2 can
experience
both interaural level differences and interaural time/phase differences that
are
adjustable and controllable.
In applications where both Rl and R2 include the system of FIGS. lA-1C,
the settings of both devices can be adjusted to achieve desired interaural
level and
interaural time/phase differences. One way of communicating settings to both
devices is to use signals embedded in the monaural information signals S1 that
are
received by R1 and R2. Thus, the monaural information is identical in such
embodiments, but the signals provided may be used to adjust Rl relative to R2.
Such embodiments require processing on wireless device 102 to provide
appropriate
control of Rl with respect to R2. It is understood that in one embodiment,
such
systems may employ a signaling that adjusts only R1, leaving R2 to operate
without
adjustment. In one embodiment, both Rl and R2 receive signals that adjust both
devices to relatively provide the desired interaural level and/or interaural
time/phase
differences. In other embodiments, the signals for such interaural differences
are
generated within Rl and/or R2. For example, in a telephone sensing embodiment,
the electronics of Rl may include a magnetic field sensor which programs Rl to
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shift to a telecoil mode (thereby turning off or diminishing the local
microphone-
received sound of the hearing assistance device R1) when a telephone is
detected at
or near RI. Many other embodiments and applications are possible without
departing from the scope of the present subject matter.
Other signaling and communications modes may be accomplished without
departing from the scope of the present subject matter. For example, FIG. 2
shows
one system of devices in a relaying communication mode according to one
embodiment of the present subject matter. The relaying can be of control
signals,
audio signals, or a combination of both. The relaying can be accomplished to
perform functions adjusting phase and amplitude of both R1 and R2 and provides
the ability to control lateralization and volume of the monaural signal to
both ears.
For example, when one ear detects a telephone signal, the relayed signal could
include instructions to shut off or diminish the local received sound to the
other ear
to better hear the caller. The relayed signal could also lateralize the sound
to the
device detecting the phone to enjoy the enhanced benefits of binaural
reception of
the caller. Such embodiments can provide relaying of the caller's voice to the
ear
without the telephone against it, albeit at the proper phase and level to
properly
lateralize the sound of the caller's voice.
New virtual communication modes are also possible. When used in
conjunction with telecommunications equipment, the system could provide a
virtual
handheld phone function without the user ever picking up the phone. For
example,
with this system, the user may answer his/her telephone (signaled from a
ringing
telephone), engage in a wireless session with his/her phone (e.g., Bluetooth
communications with a cellular phone), and the system will programmably and
automatically lateralize sound to a desired ear for binaural reception of the
caller.
All these activities can be performed without ever having to pick the phone up
or
place it near the ear. Those of skill in the art will readily appreciate a
number of
other applications within the scope of the present subject matter.
CA 02592686 2007-06-29
In some embodiments, it is possible to also insert special audio information
for playing to one or more ears based on events. For example, given the
previous
example of virtual phone, a voice could play when caller identification
identifies the
caller to let the wearer know who the caller is and to decide whether to
answer
his/her phone.
Other applications too numerous to mention herein are possible without
departing from the scope of the present subject matter.
FIG. 3 shows one system of devices in a relaying communication mode
according to one embodiment of the present subject matter. In the embodiment
of
FIG. 3 it is possible to allow one receiver (e.g., R1) to be used to receive
the
monaural signal S 1 and thereby relay the audio and/or control information to
a
second receiver (R2) in a relaying mode. The information communicated from
wireless device 302 to primary device R1 is retransmitted to secondary device
R2.
Such systems have an.additional time delay for the relay signal to reach
secondary
device R2 with the information. Thus, for synchronization of the information
timing, the system may employ delay in the primary device Rl to account for
the
extra time to relay the information to secondary device R2.
This additional relaying option demonstrates the flexibility of the system.
Other relaying modes are possible without departing from the scope of the
present
subject matter.
In the various relaying modes provided herein, relaying may be performed in
a variety of different embodiments. In one embodiment, the relaying is
unidirectional. In one embodiment the relaying is bidirectional. In one
embodiment, relaying of audio information is unidirectional and control
information
is bidirectional. Other embodiments of programmable relaying are possible
involving combinations of unidirectional and bidirectional relaying. Thus, the
system is highly programmable to adapt to a number of communication
requirements and applications.
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FIG. 4A shows one system providing multiple signals according to one
embodiment of the present subject matter. This system demonstrates that phase
and/or level adjustment may be performed at the wireless device 402 to provide
a
first signal S 1 and a second signal S2 from a single monaural signal. In some
embodiments, the signals S1 and S2 are adjusted to the desired interaural
phase/time
delay and interaural level differences by wireless device 402 and then played
to the
wearer of Rl and R2 without further adjustments to the phase and/or level. In
some
embodiments, further adjustment of the interaural phase/time delay and/or
interaural
level can be performed by either Rl or Rl or both in combination. The
adjustments
to interaural phase/time delay and/or interaural level are controllable by
inputs to the
wireless device 402 and many of the same applications can be performed as set
forth
herein.
FIG. 4B shows a signal flow of a wireless audio controller according to one
embodiment of the present subject matter. In this example, the monaural input
signal 405 is processed by phase shifter 432 to provide a phase shifted
version of the
input signa1405. In various embodiments, the phase shift arises from a
constant
time delay applied to input signa1405. In various embodiments, the phase shift
arises from a constant phase shift at all frequencies applied to input signal
405. In
various embodiments, the phase shift arises from a phase shift that is varying
as a
function of frequency. Thus, contro1438 provides some form of setting for
adjusting phase shift and/or for selecting the type of phase shift to be
applied. In
one embodiment, the signal 425 is provided by a source external to the hearing
assistance device Rl to control the phase shift. Various means for supplying
signal
425 include one or more of switches operable by a user, soft switches
programmed
by a programming device, or any combination of such inputs. Furthermore, in
various embodiments, signa1425 may be internally generated by systems within
the
programming device to provide phase shift control as a function of one or more
of
sound received, conditions detected, and other processes requiring a change of
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either phase shift amount and/or mode. The signal 425 may also be transmitted
and
received by the device to adjust its operation.
The phase adjusted signal may also be further processed using processor
434. The resulting signal is sent to radio transmitter 440 to provide S 1 and
S2 with
the desired interaural phase/time delay and interaural level adjustments.
Thus, the
phase shifter circuitry is located at the wireless device 402 in this
embodiment. In
various embodiments, the wireless device 402 includes one or more of the
interface
embodiments demonstrated in U.S. Provisional Patent Application Ser. No.
60/687,707, filed June 5, 2005, entitled: CONIlVf[JNICATION SYSTEM FOR
WIRELESS AUDIO DEVICES, and U.S. Patent Application Ser. No. 11/447,617,
filed June 5, 2006, entitled: COIVIIVIUNICATION SYSTEM FOR WIRELESS
AUDIO DEVICES which claims the benefit of U.S. Provisional Application Ser.
No. 60/687,707, the entire disclosures of which are hereby incorporated by
reference. The functionalities of the wireless audio controller can be
combined with
the phase/time delay and level adjusting features described herein. Various
different
inputs may be used in combination to perform phase/time delay adjustment
control
and interaural level adjustment control.
The system of FIG. 4 can perform many of the applications set forth above
for those systems of FIGS. 1-3. Furthermore, the systems may work in
conjunction
to provide interaural phase/time delay and interaural level adjustment of the
signals
for a variety of applications. Various different inputs may be used in
combination
to perform phase/time delay adjustment control and interaural level adjustment
control.
The following discussion applies to all of the embodiments set forth herein.
For audio applications including speech, a number of modes exist for binaural
presentation of speech to the primary device and secondary device. Binaural
speech
information can greatly enhance intelligibility of speech. This is especially
so when
speech has been distorted through a vocoder and when the wearer is attempting
to
listen in a noisy environment. The following modes also provide other
advantages
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to speech information, such as loudness summation and a release of masking
making the speech more understandable in a noisy environment.
1) Coherent Signals: When signals are coherent, the signals provided to a
wearer of, for example, a hearing aid receiving signals via the DAI interfaces
are
identical, producing a perception of centered sound to the user. Such speech
would
be diotic.
2) Incoherent Signals: A phase shift is applied across the spectrum of the
signal either in the primary or the secondary device. For example, the speech
signal
in the secondary device could be inverted, equivalent to providing a 180
degree
phase shift at all frequencies. The binaural speech will be perceived as
diffuse and
may be preferred by the wearer over the centered, diotic speech associated
with
coherent signals (above). The speech in the case of incoherent signals is
dichotic.
Those of skill in the art will know that many phase adjustments can be made to
achieve a diffuse perception, including a constant change across frequency of
a
phase value other than 180 degrees, and a frequency-varying phase change. Time-
domain filters, such as all-pass filters, can also be used to adjust the phase
of the
signal without the use of time-to-frequency conversion. One approach to
providing
such a phase shift includes conversion of the time domain signals processed by
the
system into frequency domain signals and then application of a predetermined
phase
to create the 180 degree shift for all frequencies of interest.
3) Lateralized Signals: A delay and/or attenuation is applied to the speech
in either the primary or secondary device in order for the speech to be
perceived as
coming from the side that did not receive the delay and/or attenuation.
Typical
numbers include, but are not limited to, a one millisecond delay and a one
decibel
attenuation. Typical ranges of delay include, but are not limited to, 0.3
milliseconds
to 10 milliseconds. One such other range includes 0.2 milliseconds to 5
milliseconds. Typical attenuation ranges include, but are not limited to, 1
decibel
and 6 decibels. One such other range includes 1 decibel to 10 decibels. Other
delays and attenuations may be used without departing from the scope of the
present
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subject matter. A listener may prefer, for example, a one millisecond delay
and a
one decibel attenuation, since speech from, for example, a cell phone, is
normally
heard in one ear and since the perceived sound will be in one ear, yet retain
the
benefits of having a binaural signal to the listener. In various embodiments,
the
attenuations and delays are programmed by the dispensing professional using
hearing aid fitting software. So, different patients could have different
parameters
set according to their preference. Some patients may prefer diffuse sound,
some
may prefer sound to their left, some may prefer sound to their right, etc.
The wearer's voice in various embodiments can be transmitted back to the
wireless device. For example, in cases where the wireless device is a cell
phone and
the primary and secondary wireless hearing assistance devices are hearing
aids, it is
understood that the communications back to the cell phone by the aids include:
1) In one embodiment, the primary device (e.g., hearing aid) paired with the
wireless device (e.g., cell phone) transmits the wearer's voice back to the
wireless
device (cell phone) and does not transmit this to the secondary device (e.g.,
other
hearing aid). Thus, no voice pickup is used by the secondary device and no
transmission of the wearer's voice is made from secondary device to primary
device.
2) In one embodiment, the secondary device (e.g., other hearing aid) does
transmit audio to the primary device (e.g., hearing aid paired with the cell
phone).
In varying embodiments, the signals picked up from the primary device and
secondary device can be processed in a variety of ways. One such way is to
create a
beamformed signal that improves overall signal-to-noise ratio that is
transmitted
back to the wireless device (e.g., cell phone). A delay would be added to the
primary voice-pickup signal before effective combination with the secondary
voice
signal. Such a system can steer the beam to a location orthogonal to the axis
formed
by a line connecting primary and secondary, i.e., the direction of maximum
sensitivity of the beamformed signal can be set at the location of the
wearer's
mouth. In addition to beam forming, noise cancellation of uncorrelated noise
CA 02592686 2007-06-29
sources can be accomplished. In one application, such cancellation can take
place
by the primary device prior to transmission to the wireless device. These
techniques
improve the signal-to-noise ratio and quality of the signal received by a
person
listening to the signals from the wireless device (e.g., a person at the other
end of
the communication, for example, at another telephone).
It is understood that the present phase shifter could be replaced with a
processor offering a head-related transfer function (HRTF) which performs
phase
and level changes as a function of frequency that are specific to the acoustic
transfer
function from a free field source to the ear of the listener. Such processing
could be
accomplished using a digital signal processor or other dedicated processor.
It is understood that the examples set forth herein can be applied to a
variety
of wireless devices and primary and secondary device combinations. Thus, the
examples set forth herein are not limited to telephone applications. It is
further
understood that the wireless devices set forth herein can be applied to right
and left
hearing applications as desired by the user and is not limited to any one
direction of
operation.
This description has set forth numerous characteristics and advantages of
various embodiments and details of structure and function of various
embodiments,
but is intended to be illustrative and not intended in an exclusive or
exhaustive
sense. Changes in detail, material and management of parts, order of process
and
design may occur without departing from the scope of the appended claims and
their
legal equivalents.
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