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Patent 2707284 Summary

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(12) Patent Application: (11) CA 2707284
(54) English Title: METHOD AND SYSTEM FOR DRIVING BILATERAL BONE ANCHORED HEARING AIDS
(54) French Title: PROCEDE ET SYSTEME DE COMMANDE D'AIDES DE CORRECTION AUDITIVE A ANCRAGE OSSEUX BILATERAL
Status: Dead
Bibliographic Data
(51) International Patent Classification (IPC):
  • A61F 11/04 (2006.01)
  • H04R 25/00 (2006.01)
(72) Inventors :
  • DEAS, ROSS W. (Canada)
  • ADAMSON, ROBERT BRUCE ALEXANDER (Canada)
  • BANCE, MANOHAR (Canada)
  • BROWN, JEREMY A. (Canada)
(73) Owners :
  • DEAS, ROSS W. (Canada)
  • ADAMSON, ROBERT BRUCE ALEXANDER (Canada)
  • BANCE, MANOHAR (Canada)
  • BROWN, JEREMY A. (Canada)
(71) Applicants :
  • DEAS, ROSS W. (Canada)
  • ADAMSON, ROBERT BRUCE ALEXANDER (Canada)
  • BANCE, MANOHAR (Canada)
  • BROWN, JEREMY A. (Canada)
(74) Agent: BORDEN LADNER GERVAIS LLP
(74) Associate agent:
(45) Issued:
(22) Filed Date: 2010-06-11
(41) Open to Public Inspection: 2011-12-11
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract




Current bilateral BAHA configurations, for sounds directly facing a listener,
apply forces to
the skull that are in-phase with each other and directed towards the center of
the head.
The head's response approximates that of a rigid body at frequencies < 1000Hz,
thus it is
preferable to drive bilateral BAHAs such that when one pushes, the other
pulls. Adjusting
the relative phase offset of BAHAs, achieves this, resulting in greater
vibration and
improved hearing.


Claims

Note: Claims are shown in the official language in which they were submitted.




CLAIMS:

1. A method of driving bilateral bone anchored hearing aids, comprising:
sensing sound waves at a microphone;
driving the bilateral bone anchored hearing aids out of phase in response to
low
frequency sound waves, such that one of the bilateral bone anchored hearing
aids
pushes towards a wearer's skull, while the other of the bilateral bone
anchored hearing
aids pulls away from the skull, thereby generating bone vibration to excite
the movement
of cochlear fluids.


2. The method of claim 1, wherein driving the bilateral bone anchored hearing
aids
comprises driving the bilateral bone anchored hearing aids 180° out of
phase.


3. The method of claim 1, wherein driving the bilateral bone anchored hearing
aids
comprises driving the bilateral bone anchored hearing aids at frequencies
below 1000Hz.

4. A bilateral bone anchored hearing aid (BAHA) system, comprising:
bilateral abutments anchored to a wearer's skull;
an vibration actuator attached to each abutment;
driving circuitry for driving each electromagnetic vibration actuator in
response to
sound waves sensed by a microphone associated with each electromagnetic
vibration
actuator, the driving circuitry being configured to drive the electromagnetic
vibration
actuators out of phase with respect to each other, such that as force is
applied towards
the wearer's skull on one side, and away from the wearer's skull on the
opposing side,
thereby generating bone vibration to excite the movement of cochlear fluids.


5. The BAHA system of claim 4, wherein the driving circuitry comprises digital
signal
processing means.


6. The BAHA system of claim 4, wherein the vibration actuators are attached to
the
abutments through a snap coupling.


7. The BAHA system of claim 4, wherein the abutments are implanted titanium
fixtures.


8. The BAHA system of claim 4, wherein the vibration actuators comprise
electromagnetic vibration actuators.


-13-



9. The BAHA system of claim 8, wherein the electromagnetic vibration actuators

comprise an electromagnetic motor driving a counterweight.


10. The BAHA system of claim 4, wherein the vibration actuators comprise
piezoelectric vibration actuators.


-14-

Description

Note: Descriptions are shown in the official language in which they were submitted.



CA 02707284 2010-06-11

METHOD AND SYSTEM FOR DRIVING BILATERAL BONE ANCHORED
HEARING AIDS

FIELD
[0001] The present disclosure relates generally to bone anchored hearing aids
(BAHAs). More particularly, the present disclosure relates to a method and
system for
driving a BAHA.

BACKGROUND
[0002] The bone anchored hearing aid (BAHA) is an effective implantable
prosthesis for patients with conductive hearing loss, who, for various reasons
(i.e. chronic
infections in ear canal), are unlikely to benefit from traditional air
conduction hearing aids
(Tjellestrom et al. 2001). The BAHA has traditionally been indicated for
moderate to
severe conductive hearing loss, but may also be used in cases of moderate
sensorineural
loss or mixed loss. More recently it has been used for contralateral routing
of sound
(CROS) applications for unilaterally deaf patients (Niparko et al. 2003;
Stenfelt 2005).
[0003] Typically, the BAHA consists of a microphone, amplification and signal
processing electronics and an electromagnetic vibration actuator that is
attached through
a snap coupling to an implanted titanium fixture called an abutment. The
abutment is
screwed 4 mm into the skull, where it osseointegrates into the temporal bone,
providing a
stiff mechanical coupling to the bone.
[0004] Bone vibrations are transformed into sound by a number of processes,
most notably the inertial movement of the inner ear ossicles and inner ear
fluids which
dominates at low frequencies, compression of the cochlear shell, and sound
radiation
from the vibrations in the skull to the external and middle ear spaces
(Tonndorf, 1966,
Stenfelt & Goode 2005). From the point of view of perceived hearing, cochlear
vibrations
caused by bone vibration are entirely equivalent to those caused by air-
conducted sound.
In fact, bone-borne and air-borne vibrations can be made to cancel each other
in the
cochlea (von Bekesy 1932; Stenfelt, 2007).
[0005] The BAHA generates bone vibration with an electromagnetic motor that
pushes a counterweight mass within its housing. This generates a reactive
force into the
abutment that drives vibration of the skull. At low frequencies below 1000 Hz,
these
vibrations act to move the entire head in phase (H6kansson et al. 1993;
Stenfelt & Goode
2005), and it is useful to think of the head as being a single rigid mass.
Above 1000 Hz,
the time taken for acoustic energy to propagate across the skull becomes
comparable to
the period of the oscillation. Consequently different parts of the skull
become mutually out
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CA 02707284 2010-06-11

of phase, and the skull can no longer be thought of as a single rigid body. At
all
frequencies the BAHA delivers sound to both cochleae. Although there is some
evidence
for attenuation of sound in crossing the skull at the highest frequencies
(Nolan & Lyons
1981; Stenfelt & Goode 2005), this attenuation is generally considered to be
less than
10dB.
[0006] Given that a single BAHA transmits sound to both cochleae, and that
fitting
a second device is associated with additional financial cost along with the
risks
associated with additional surgical procedures, it might be thought that there
is no benefit
to fitting a second BAHA, particularly since a second device yields only a
modest
improvement in audiological thresholds (Priwin et al. 2004). However,
bilateral BAHAs are
associated with greater quality of life (Ho et al. 2009) and improved
performance in a
number of listening situations.
[0007] Investigations into the efficacy of bilateral BAHAs relative to
unilateral
BAHAs have shown, fairly consistently, that localization ability improves (Van
der Pouw et
al. 1998; Bosman et al. 2001; Priwin et al. 2004). Azimuthal localization
improvements
are presumably due to the different azimuthal dependence of the signals
received by the
two microphones in the presence of head shadow and interaural delay effects
(Rayleigh,
1907). In addition to superior localization ability, different measures of
speech perception
show improvements with bilateral BAHAs relative to unilateral BAHAs (Van der
Pouw et
al. 1998; Bosman et al. 2001; Duff et al. 2002; Priwin et al. 2004). It has
been shown,
fairly consistently, that speech perception in quiet, measured by the level
needed for
accurate speech comprehension, improves with bilateral BAHAs relative to
unilateral
BAHAs (Van der Pouw et al. 1998; Bosman et al. 2001; Priwin et al. 2004).
Bilateral
BAHAs yield some improvement for speech in noise, relative to unilateral
BAHAs,
although these improvements are smaller (Van der Pouw et al. 1998; Bosman et
at. 2001;
Priwin at al. 2004). Therefore fitting bilateral BAHAs may result in
additional benefit that
goes beyond the simple doubling in power that results from two amplifiers and
transducers.
[0008] Given the potential benefit of bilateral BAHAs relative to unilateral
BAHAs,
it seems pertinent to attempt to establish optimal configuration for two
devices that work
in tandem on the same skull. Currently, bilateral BAHAs are not differentiated
into left and
right versions, except in some models where the microphone placement is
changed to
make them cosmetically symmetric. This means that in response to a positive
pressure at
the microphone, both bilateral BAHAs will generate a force directed inward
towards each
other or outwards away from each other as shown in Figure 1a. We say that the
two
BAHAs act in phase. The result is that to the extent that the skull can be
thought of as a
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CA 02707284 2010-06-11

rigid body, particularly at low frequencies, the forces from the two BAHAs
substantially
cancel each other.
[0009] It is, therefore, desirable to provide an improved method and system
for
driving bilateral BAHAs that improves their efficiency, particularly at low
frequencies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Embodiments of the present disclosure will now be described, by way of
example only, with reference to the attached Figures.
[0011] Figure 1: Illustration of forces applied to the skull for low frequency
sounds
when bilateral BAHAs operate (a) in phase and (b) out of phase. These figures
illustrate
that at frequencies where the head moves as a solid mass (i.e. below 1000Hz),
larger
motion is experienced when BAHAs are out of phase.
[0012] Figure 2: Change in threshold for bilateral BAHAs relative to the
unilateral
BAHA. Data is displayed for each frequency tested, for in phase (triangles)
and out of
phase (squares) bilateral BAHA configurations. Error bars reflect SEM.
Negative values
reflect an improvement relative to unilateral thresholds.
[0013] Figure 3: Measurements of the velocity of the cochlear promontory on
the
cadaver head for in- phase and out-of-phase bilateral BAHAs. The four graphs
give the
magnitude of the velocity and the components in the vertical (x), Frankfurt
line (y) and
interaural (z) directions. Measurements are given relative to the velocity
measured with a
single BAHA driving the head.
[0014] Figure 4: Velocity of the cochlear promontory under various driving
conditions. From left to right, the graphs give the velocity under bilateral
in-phase drive,
bilateral out-of-phase-drive, and unilateral drive. The measured vibration
levels of
hundreds of pm/s to 1 mm/s are typical of the BAHA Divino's maximum output.
DETAILED DESCRIPTION
[0015] Generally, the present disclosure provides a method and system for
driving
bilateral BAHAs. The BAHAs are driven out of phase, such that in response to
positive
sound pressure one BAHA applies a force directed into the head and the other
applies a
force directed out of the head as shown in Figure 1 b. Such a "push-pull"
configuration is
more efficient at moving the skull and hence at creating bone-conducted
hearing.
[0016] Changing from in-phase to out-of-phase driving can be implemented in
many ways. Modifications to the driving circuitry or digital signal processing
can be easily
effected. It could, for instance, be achieved by swapping the electrical leads
attached to
either the microphone or the electromagnetic motor. In newer BAHAs that
incorporate a
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CA 02707284 2010-06-11

digital signal processing unit, the phase flip could be achieved by changing
the signal
processor firmware.
[0017] The effect of driving two BAHAs out of phase has been examined, and
results in lower thresholds of hearing for the same electrical power draw. We
compare
performance of bilateral BAHAs driven in this configuration to the standard
configuration.
In twelve normal participants we show significant improvements in low-
frequency (
<1000Hz) hearing thresholds using out-of-phase BAHAs. This is further
supported by
velocimetric measurements taken at the cochlear promontory in a cadaveric
head.
Comparing vibration arising from each configuration confirms that out-of-phase
driving
results in greater vibration. Our first experiment compares audiometric
hearing thresholds
for unilateral BAHAs and bilateral BAHAs where phases are equal and where
phases are
opposite. This is tested in participants who are audiologically normal. In the
second study,
the 3D velocity at the cochlear promontory of a cadaver head is measured.
Vibration level
arising from in phase and out of phase bilateral BAHAs are compared across a
range of
frequencies.

METHODS: AUDIOLOGICAL MEASUREMENTS

[0018] Subjects. Twelve normal hearing participants were tested in this study
(8
males). Ages ranged from 27 to 48 years old, with a mean of 35.67 years old
(S.D 7.808).
All had bone thresholds better than 25 dB in the frequency range 250-4000Hz
with the
exception of one participant, who had a mild high frequency hearing loss at
4000Hz.
Informed consent was obtained from each participant prior to their
participation in the
study.
Instrumentation. All testing was completed in a sound isolated double walled
sound booth
(Industrial Acoustics Inc.), with the subject seated in the booth and the
tester outside. The
ambient noise level of the booth met ANSI specifications for threshold
testing. Two
electromagnetic motors removed from BAHA Intenso (Cochlear Corp.) devices were
used
as the bone actuator. These were driven directly by a Grason-Stadler 61
Clinical
Audiometer calibrated to ANSI specifications (S3.6-1996). Phase was controlled
using a
phase inverter which ran between the motor and audiometer and acted to reverse
the
polarity of the electrical signal applied to the motor. Prior to experimental
testing it was
confirmed that the phase inverter did not affect audiological thresholds, and
the output as
measured by an accelerometer was the same for both BAHAs with, and without the
phase inverter.

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CA 02707284 2010-06-11

[0019] Procedure. Bone conduction thresholds were collected for 250, 500, 750,
1000, 1500, 2000, 3000 and 4000 Hz, using unilateral, bilateral in-phase
(opposing
forces), or bilateral out-of-phase (co-directed forces) BAHAs.
[0020] The BAHA motor was placed on the participant's head, held in place by a
metal headband, and placed on the usual BAHA site of 50-55mm from the ear
canal at
either the 10 o'clock or the 2 o'clock position, for the right and left sides
respectively.
Three experimental conditions were run. In the single BAHA condition, one
motor was
placed on either the left or right side of the head. Placement side was
randomized. In the
"in-phase" condition, two BAHAs were placed on the left and right BAHA sites
and were
driven from the same electrical signal. In the "out-of-phase" condition, one
of the BAHAs
was driven through the phase inverter. To eliminate any experimental bias,
both the
participant and the clinician measuring thresholds were blind to the
experimental
condition being tested. To minimize the chance that small differences in force
or device
placement (e.g. Dirks 1964) could potentially contaminate our results,
thresholds were
obtained three times for each condition, spread across three experimental
sessions. Each
individual session consisted of the three experimental conditions presented in
a random
order. Data were only accepted for participants with good test-retest
reliability, as
measured by reliability coefficients. Threshold was taken to be the mean HL
obtained
across three trials.

RESULTS: AUDIOLOGICAL MEASUREMENTS
Test-retest reliability
[0021] Test retest reliability was high. For each participant, reliability
coefficients
were calculated. Reliability coefficients (r) for the three tests in each
condition and for
each participant exceeded 0.7. Therefore, threshold for each frequency was
taken as the
mean of the three thresholds obtained within each condition.
Differences in thresholds
[0022] To compare performance of bilateral in phase and out of phase BAHAs,
the difference from baseline (single BAHA) was calculated for each of the
frequencies
tested. These data are plotted in Figure 2, with the change in threshold (y-
axis) plotted
against the frequencies tested (x-axis) for the out of phase condition
(squares) and the in
phase condition (triangles). Negative values reflect an improvement in
threshold. Error
bars reflect standard error of the mean.
[0023] Figure 2 shows a small (3-6dB HL) improvement in audiometric thresholds
for bilateral out-of-phase BAHAs relative to bilateral in-phase BAHAs at low
test

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CA 02707284 2010-06-11

frequencies (below 1000Hz). A repeated measures two-way ANOVA revealed
significant
main effects of phase (f(1,11)= 16.02, p<0.01) and of frequency (f(7,77)=3.36,
p<0.05).
The analysis also revealed a significant interaction between phase and
frequency
(f(7,77)=3.56, p<0.01). To establish at which frequencies phase has a
significant effect,
repeated measures one-way ANOVAs were carried out at each frequency. These
analyses showed significantly lower thresholds in the out-of-phase condition
than in the
in-phase condition at 250 (f(1,11)=16.20, p<0.01), 500 (f(1,11)=29.36,
p=<0.01) and 750
Hz (f(1,11)=4.90, p<0.05). There was no significant difference at any other
frequency. We
conclude that at frequencies below 1000Hz, bilateral out of phase BAHAs yield
significantly lower thresholds than bilateral in phase BAHAs and that at no
frequency do
they significantly increase thresholds.

METHODS: LASER DOPPLER VELOCIMETRY

[0024] Out-of-phase and in phase driving was also studied on an embalmed head
where, unlike in living subjects, detailed velocimetry of the motion of the
cochlear
promontory was possible. The head was from a female, aged between 60 and 70
years
that had been deceased approximately 6 months at the time of the experiment.
The
embalming procedure consisted of an injection of 40-60 L of embalming fluid
through the
femoral artery, followed by another 20 L of hypodermic injection at various
sites. At the
time of testing the head weighed 3730 grams.
[0025] Measurements were performed with a Polytech CSV-3D (Polytech GmbH,
Waldbronn, Germany) 3D laser Doppler vibrometer which was capable of
simultaneously
measuring the magnitude and direction of the velocity of a 150 m diameter
area on a
surface. In order to have the laser beams reach the cochlea, the ear canal was
widened
to 2 cm in diameter and the tympanic membrane and ossicular chain removed. The
lasers
shone directly on the cochlear promontory.
[0026] Two BAHA abutments were implanted into the embalmed head using
methods similar to standard surgical implantation. The abutments were
positioned 55 mm
behind the ear canal at either the 10 o'clock or the 2 o'clock position. A
pilot hole was
drilled and the self-tapping abutment screwed 4 mm into the skull using a
wrench
designed for abutment implantation.
[0027] Two motors removed from BAHA Divinos (Cochlear Corp, Australia) were
used to drive the abutments. Both BAHAs were driven through an 8-ohm Crown
audio
amplifier, and the phase of one was reversed by swapping the wires driving the
motor.
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CA 02707284 2010-06-11

t0028] The .CLV-3D produced an..autput voltage proportional to the:valocity
along
three axes, which were carefully aligned, to the interaural, Frankfurt line
(connecting. the
inferior, orbital ridge to the center of.the aperture of the, external
auditory mpatus),,and.
vertical directions. The BAHAs were harmonically excited by a 1VRMS sine wave
that
was stepped through 200 frequencies from 1b0 610,000 Hz. 0.5 seconds-were
allowed
for any, transient response of the skull tostablkze, folio pd by. 1second
aGgwsiton at
each frequency. The output voltage of the-LDV'system was acquired Vith
a'44channel'
National Instruments (Austin,TX) PCI-4452 data acquisition card controlled by
a custom
Labview interface.

RESULTS

[0029] Measurements were obtained for bilateral in-phase, bilateral out-of-
phase
and unilateral conditions. Figure 3 shows the results. In order to facilitate
comparison with
the audiological data, the velocities for the two bilateral conditions were
referenced to the
unilateral condition and the y-axis of the plots reversed so that larger
velocities relative to
the unilateral condition are lower on the y-axis. In order to give the reader
a sense of the
absolute size of the three velocity components, all three components are
plotted for the
three conditions separately in Figure 4. At low frequencies the velocity is
primarily
directed along the interaural.direction z because the force of the BAHAs is
primarily
directed along this direction. The fact that the force and response of the
head are parallel
is indicative of rigid body motion. At higher frequencies this is no longer
true. Averaged
over frequencies, the three directions have roughly similar levels above 1000
Hz,
although at any given frequency one or the other direction may dominate. This
behavior is
indicative of non-rigid modal vibration.
[0030] Several qualitative features are strikingly similar between the
audiological
and velocimetric data. In both cases there is a clear separation into high
frequency and
low frequency regimes. In the high frequency regime there is no clear
advantage to in
phase versus out of phase driving, whereas in the low frequency regime the out-
of-phase
condition results in significantly higher velocities than the in-phase
condition. The
cadaveric data shows that the increase in velocity is strongly directionally-
dependent, with
the interaural direction showing a difference between the in-phase and out-of-
phase
driving conditions as large as 30 dB. In the Frankfurt-line direction, the in
phase condition
produces a 15 dB higher velocity than the out of phase component, although the
absolute
level of motion in this direction is much smaller than the motion in the
interaural direction.
Relative to the unilateral condition, the vector sum of the three velocity
components

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CA 02707284 2010-06-11

shows an increase of between 5 and 8 dB for the out of phase condition and
between -2
and 4 dB for the in phase condition. These changes correspond very well with
the
observed change in audiological hearing level in the test subjects. It has
been asserted
by others (Stenfelt & Goode 2005) that velocity magnitude appears to be more
strongly
correlated with hearing level than motion along any particular direction. Our
measurements support this assertion.

DISCUSSION
[0031] The two experiments described in this paper strongly suggest that
clinical
gains obtained from bilateral BAHAs can be optimized by offsetting signal
phase of one
device relative to another. Data obtained at the level of the promontory in a
cadaveric
head supports audiological data obtained from humans to provide a compelling
argument
for offsetting the phase of bilateral BAHAs. Both datasets show that
improvements
associated with out-of-phase bilateral BAHAs are significant at frequencies
below
1000Hz, while frequencies above this are not significantly affected by the
phase offset
either positively or negatively. The improvements we have observed in hearing
thresholds
for bilaterally implanted BAHA patients can be implemented with a very small
change in
the way that BAHAs are currently manufactured and fitted. Particularly in new
programmable BAHA designs, programming the relative phase between the
microphone
signal and force output should be extremely easy, allowing even a frequency-
dependent
phase to be programmed in. Our results suggest that making the phase offset a
standard
part of the BAHA fitting procedure will result in improved low frequency
hearing.
[0032] We know of no disadvantage to applying our technique. In particular
there
is no obvious reason to think that applying different phases at the two BAHAs
should
reduce the improvements in speech comprehension and localization ability
observed for
bilateral BAHAs. On the contrary, given that a common complaint of BAHA users
is that
they sound "tinny" (Stephens et al. 1996), with an over-emphasis on the high
frequencies,
an improvement in low frequency loudness can be expected to have a beneficial
effect on
perceived sound quality, and possibly on speech comprehension.
[0033] A few points of experimental methodology deserve further discussion.
The
decision not to simulate a conductive loss on the normal-hearing participants
was
motivated by the concern that plugging the ears would result in occlusion
effects
(Goldstein & Hayes 1965). The occlusion effect was expected to improve low
frequency
thresholds by as much as 20 dB HL below 1000 Hz. As these are the frequencies
of
primary interest in this study, it was deemed that plugging, by introducing an
effect

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CA 02707284 2010-06-11

considerably larger than the one being measured, could complicate the
experiment.
Because participants' ears were left open, it could be argued that thresholds
arise not
because of bone-conduction, but rather by air-conduction that arises from
radiation from
the BAHA. We argue that this is, however, extremely unlikely for a number of
reasons:
Firstly, the amount of radiation caused by the device is negligible,
especially at the
threshold levels at which we are presenting the stimuli. Furthermore, if
thresholds arose
from air conduction it is unclear why there would be a differential effect of
phase across
conditions. This effect is consistent across participants, and is consistent
with
measurements obtained from the promontory of cadaveric heads which were
completely
insensitive to air-borne sound. We are therefore confident that the effects
measured are
due to bone conduction and not air conduction.
[0034] Laser Doppler vibrometry on a cadaver head showed that out-of-phase
bilateral BAHAs create a greater level of motion than either bilateral in
phase BAHAs or a
unilateral BAHA, with the level of improvement typically 5-8 dB relative to a
unilateral
BAHA. This agrees quite well with our audiological findings showing a 4-6 dB
improvement at the frequencies measured.
[0035] Though small, the observed improvements in audiological thresholds are
of obvious clinical benefit, particularly as the low frequencies (500 and
750Hz) are
involved in speech perception (French & Steinberg 1947). Improved ability to
perceive
speech is the primary motivator for patients to seek treatment (Crowley &
Nabelek 1996;
Garstecki & Erler 1998) and impaired speech perception is regularly reported
by people
with hearing impairments (Gatehouse & Noble 2004).
[0036] A number of studies have shown that traditional in-phase bilateral BAHA
configurations yield improvements in speech comprehension both in quiet, and
in noise. It
is important to establish whether the improvement offered by out-of-phase
BAHAs
translates to improved speech comprehension. Of equal importance is
establishing how
the out of phase bilateral BAHA configuration affects sound localization.
Improving
localization performance is a key factor in fitting bilateral BAHAs as, in
addition to
avoiding environmental hazards, aids people listening to speech in noise
(Freyman et al.
1999). This low-frequency improvement in performance will only be useful if it
does not
interfere with speech and localization capabilities. These are situations that
our laboratory
intends to investigate.
[0037] This study shows that by offsetting the phase of one BAHA in a
bilateral
BAHA pair, improvements of up to 6dB (equivalent to a doubling of loudness)
are seen in
the low frequencies, relative to regular bilateral configurations. This
improvement can be
achieved with very simple change in BAHA design or fitting, and can be used
either to
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CA 02707284 2010-06-11

increase perceived loudness or to reduce power consumption at a given
loudness. We
conclude that when designing BAHAs intended for bilateral use, manufacturers
should
consider offsetting the phase of one device relative to another.
[0038] In the preceding description, for purposes of explanation, numerous
details
are set forth in order to provide a thorough understanding of the embodiments.
However,
it will be apparent to one skilled in the art that these specific details are
not required. In
other instances, well-known electrical structures and circuits are shown in
block diagram
form in order not to obscure the understanding. For example, specific details
are not
provided as to whether the embodiments described herein are implemented as a
software
routine, hardware circuit, firmware, or a combination thereof.
[0039] The above-described embodiments are intended to be examples only.
Alterations, modifications and variations can be effected to the particular
embodiments by
those of skill in the art without departing from the scope, which is defined
solely by the
claims appended hereto.

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CA 02707284 2010-06-11
REFERENCES

The following references are incorporated herein by reference in their
entirety:
Bosman, A.J., Snik, A.F.., van der Pouw, C.T., Mylanus, E.A., Cremers, C.W.
(2001).
Audiometric evaluation of bilaterally fitted bone anchored hearing aids. Int J
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Representative Drawing
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Administrative Status

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Title Date
Forecasted Issue Date Unavailable
(22) Filed 2010-06-11
(41) Open to Public Inspection 2011-12-11
Dead Application 2013-06-11

Abandonment History

Abandonment Date Reason Reinstatement Date
2012-06-11 FAILURE TO PAY APPLICATION MAINTENANCE FEE

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Application Fee $400.00 2010-06-11
Owners on Record

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Current Owners on Record
DEAS, ROSS W.
ADAMSON, ROBERT BRUCE ALEXANDER
BANCE, MANOHAR
BROWN, JEREMY A.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Abstract 2010-06-11 1 11
Description 2010-06-11 12 601
Claims 2010-06-11 2 46
Drawings 2010-06-11 3 47
Representative Drawing 2011-10-26 1 5
Cover Page 2011-11-22 1 34
Assignment 2010-06-11 3 94