U.S. patent application number 11/722287 was filed with the patent office on 2012-02-09 for nano-otologic protective equipment for impact noise toxicity and/or blast overpressure exposure.
This patent application is currently assigned to PRESIDENT AND FELLOWS OF HARVARD COLLEGE. Invention is credited to Brendan Clifford, John W. Hutchinson, Eben Oldmixon, Rick Rogers, Howard A. Stone, Robert M. Westervelt.
Application Number | 20120033823 11/722287 |
Document ID | / |
Family ID | 38257115 |
Filed Date | 2012-02-09 |
United States Patent
Application |
20120033823 |
Kind Code |
A1 |
Rogers; Rick ; et
al. |
February 9, 2012 |
NANO-OTOLOGIC PROTECTIVE EQUIPMENT FOR IMPACT NOISE TOXICITY AND/OR
BLAST OVERPRESSURE EXPOSURE
Abstract
An apparatus for preventing hearing loss having a body made of a
soft compliant material having first and second ends and a channel
extending therethrough, an acoustically limp material adjacent one
of the ends of the body with the acoustically limp material having
a hole therein aligned with the channel extending through the body,
and a component film, disc or other structure covering or sealing
the opening in the acoustically limp material. The film or disc may
be formed of a high-strength polymer material and may be less than
10 micrometers in thickness. Rather than having a single channel
extending through the body, a plurality of channels may extend
therethrough and a plurality of corresponding holes may be provided
in the acoustically limp material. The film, disc or other
structure covers or seals the plurality of holes in the
acoustically limp material. The film, disc or other structure may
be attached in such a fashion as to behave like a flap whose
operation is to close in response to high energy sound waves. The
flap is pressed shut from the high intensity shock wave itself. The
body may cylindrical in shape or may have another shape to fit
snugly in a human ear canal.
Inventors: |
Rogers; Rick; (Needham,
MA) ; Clifford; Brendan; (Encinitas, CA) ;
Westervelt; Robert M.; (Lexington, MA) ; Hutchinson;
John W.; (Cambridge, MA) ; Stone; Howard A.;
(Brookline, MA) ; Oldmixon; Eben; (Hyde Park,
NY) |
Assignee: |
PRESIDENT AND FELLOWS OF HARVARD
COLLEGE
Cambridge
MA
|
Family ID: |
38257115 |
Appl. No.: |
11/722287 |
Filed: |
January 10, 2007 |
PCT Filed: |
January 10, 2007 |
PCT NO: |
PCT/US2007/060346 |
371 Date: |
July 15, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60757673 |
Jan 10, 2006 |
|
|
|
60747246 |
May 15, 2006 |
|
|
|
Current U.S.
Class: |
381/72 |
Current CPC
Class: |
A61F 11/08 20130101 |
Class at
Publication: |
381/72 |
International
Class: |
A61F 11/06 20060101
A61F011/06 |
Claims
1-10. (canceled)
11. An apparatus for preventing hearing loss comprising: a power
supply; an energy activated sensor; an input device for receiving
sound; an output device for transmitting signals toward an eardrum;
a vacuum tube chamber substantially between said input device and
said output device; and a membrane surrounding at least said input
device, said vacuum tube chamber and said output device.
12. An apparatus for preventing hearing loss according to claim 11,
wherein at least said input device, said output device, said vacuum
tube chamber and said membrane form at least part of an assembly
that fits within a person's ear canal.
13. An apparatus for preventing hearing loss according to claim 11,
wherein the energy activated sensor comprises a housing and a
plurality of diodes.
14. An apparatus for preventing hearing loss according to claim 11,
wherein the energy activated sensor comprises: a flexible membrane;
a mirrored element connected to said flexible membrane such that
said mirrored element is displaced in a first direction during an
acoustic shock wave; an LED; a first diode detector array; a second
diode detector array; and a switch; wherein said LED transmits
light toward said first diode detector array; during a normal
operation said first diode detector array receives said light from
said LED, thereby causing said switch to be in a first states; and
during reception of an acoustic shock wave, said mirrored element
is displaced to a position in which is deflects said light from
said LED away from said first diode detector array and toward said
second diode array, thereby causing said switch to be in a second
state.
15. A apparatus for preventing hearing loss comprising: an assembly
comprising: first and second reflecting discs; an elastic
nanoparticle balloon between said first and second reflecting
discs, said balloon comprising a membrane filled with nanoparticles
and a low viscosity fluid, wherein said nanoparticles form a
disc-like structure when said balloon is compressed; a membrane
surrounding said assembly; an energy activated sensor; and an
energy source for supplying energy to said assembly and said
sensor.
16. A apparatus for preventing hearing loss comprising: an assembly
comprising: first and second pairs of reflecting discs; a first gel
spacer between said first pair of reflecting discs; a second gel
spacer between said second pair of reflecting discs; an elastic
nanoparticle balloon between on of said first pair of reflecting
discs and one of said second pair of reflecting discs, said balloon
comprising a membrane filled with nanoparticles and a low viscosity
fluid, wherein said nanoparticles form a disc-like structure when
said balloon is compressed; a membrane surrounding said assembly;
an energy activated sensor; and an energy source for supplying
energy to said assembly and said sensor.
17. An apparatus for preventing hearing loss comprising: a housing
having first and second ends, a length of said housing extending
between said first and second ends; a first plurality of empty
microtubes substantially parallel to said length of said housing; a
second plurality of microtubes substantially parallel to said
length of said housing, wherein each of said second plurality of
microtubes is substantially filled with a stack of discs, wherein
each said disc comprises a body, at least one sound aperture, an
alignment pad and a disalignment pad; a first winding around each
of said second plurality of microtubes for causing alignment of
said apertures in said stack of discs in said microtube; and a
second winding around each of said second plurality of microtube
for causing disalignment of said sound apertures in said stack of
discs in said microtube.
18. An apparatus for preventing hearing loss comprising: a housing;
a power supply; a field coil; an energy-activated switch; and an
antenna; wherein said switch activates said field coil to generate
an electromagnetic field that is directed by said antenna toward a
cochlea of an ear when an acoustic shock wave is received at said
switch to substantially paralyze outer hair cells on said cochlea
during said acoustic shock wave.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of the filing of
U.S. Provisional Patent Application Ser. No. 60/757,673 filed on
Jan. 10, 2006 by inventors Rick Rogers, Brendan Clifford and
Oldmixon Eben entitled "Nano-Otologic Protective Equipment for
Impact Noise Toxicity and/or Blass Overpressure Exposure" and U.S.
Provisional Patent Application Ser. No. 60/747,246, filed on May
15, 2006 by inventors Richard Rogers, Brendan Clifford, Robert
Westervelt, John Hutchinson, and Howard Stone entitled "Sound
Aperture Protective Equipment for Impact Noise Toxicity and/or
Blass Overpressure Exposure."
[0002] The aforementioned prior application is hereby incorporated
by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0003] Not Applicable.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The present invention relates to the field of prevention of
post-concussive hearing trauma, and more specifically to physical
devices, designed to be worn in the ear canal or affixed to the
outer ear to block extreme shock wave damage to the hearing
organ.
[0006] 2. Brief Description of The Related Art
[0007] There is a need for devices that provide protection from
blast overpressusre as experienced by military personnel on a
battlefield. Communication is the single most important asset of
our battlefield forces. Combat elements function as a team and must
be able to immediately react to unanticipated operational
contingencies. Instantaneous and uninterrupted communication is
fundamentally important and great effort has been made to insure
efficient and redundant communication within and among tactical
units in the field. However, a crucial aspect of this communication
network has been overlooked--blast induced hearing loss. Frontline
troops injured by explosions currently experience 64% hearing loss,
and represent an instantaneous reduction in the immediate effective
in-theater force, affecting the most critical element in the entire
chain--the advance-line soldier.
[0008] For over 500 years, national entities have used explosive
charges to wage war. Front line medical assets; improvements in
surgical techniques and the creation of Shock Surgical Trauma Teams
have significantly reduced the mortality radius from explosive
impacts. Use of individual protective gear and body armor mitigate
dismemberment and secondary limb damage in range of explosives
allowing prolonged duration of the effective force on the
battlefield. Hearing damage encountered in what we term the
otologic disablement zone extending hundreds of meters away from
the impact area remains an unaddressed component of battlefield
morbidity and tactical incapacitation.
[0009] In regional proximity to the target, an explosive charge can
produce a high-pressure shock wave with specific physical pressures
which not only rupture the eardrum, displacing the middle ear
ossicles, but also destroy inner ear sensory cells in the specific
frequency ranges most utilized for interpersonnel communication.
This acute hearing loss results from sharp impulse rise in sound
wave intensity produced by proximity to battlefield explosions. The
damage is immediate and irreversible. Soldiers within the otologic
disablement zone often do not exhibit any outward sign of hearing
impairment just after exposure other than being unable to respond
to commands. Battlefield management of the effective force assets
become secondarily compromised when the disabled team members are
unable to respond to commands. This loss of unit cohesion impedes
the attainment of mission objectives. Valuable time is lost as the
effective force adapts to this compromised situation.
[0010] According to the office of the Army Surgeon General, hearing
loss in soldiers sustained to blast injuries are running 64%, by
far the highest category of battlefield injuries, resulting in
significant reduction in effective force in the current War Against
Terrorism. The year 2004 had the highest rate of increase in combat
injuries hearing loss since records began to be kept in the mid
20.sup.th century, a period that included for example; WWII, the
Korean War, The Vietnam Conflict, the Marine deployment in Lebanon,
The Gulf War, and OIF/OEF.
[0011] In the 2005 survey of hearing protector efficacy, under
operational conditions, it was found that all the tested devices
attenuated C-weighted peak level to less than 130 dB, well below
the sound peaks experienced in explosions encountered in OIF. In
practice, these devices attenuated noise by only 10-30 dB.
[0012] Proximity to explosion is more important that size. Studies
on conventional bomb blasts ranging from 1 to 20 kg of TNT
confirmed that proximity to explosion is more important to the size
of the charge. At distances greater than 6 meters victims will
probably not have mortal wounds. A SCUD missile explosion in
military personnel housing injured the ears of 172 individuals. Of
the 86 hospitalized, 76% had ear drum perforations. Distances to
explosion were measured and used to construct mathematical model of
estimated wave form. Fifty percent of soldiers will sustain a ear
drum perforation at 185 dB (15 PSI).
[0013] Middle ear damage, such as Tympanic membrane perforation is
always an indication of cochlear damage. An important point
requires consideration. Tympanic membranes can be surgically
repaired. However, there are no medical/surgical procedures to
repair cochlear damage.
[0014] As in military applications, protection to the hearing organ
is important in occupational and industrial settings. Impact noise
in the industrial sector presents a problem similar to blast
overpressure in the military sector. According to the U.S.
Department of Labor, 28.4 per 10,000 workers will have recordable
hearing loss.sub..(2004) US Dept Labor. Ten million have
experienced permanent hearing loss, 30 million are exposed to
dangerous noise levels daily (NIOSH)
[0015] Industrial Devices such as electronic ear muffs amplify
outside noise so those with impaired hearing can hear warning
bells. The problem is that they transmit noise and directed
communication with equal intensity making no distinction between
the two. Although they do not electronically transmit noise over a
set dB range (often set to >85 dB), they are unable to intercept
harmful sound energy which continue onto the middle and inner ear
unabated.
[0016] A decibel is a sound pressure level. A whisper is 20-30 dB,
normal speech is approximately 50-60dB. A jet engine at 30 meters
is 150 dB. A loud factory is 90 dB. A pneumatic hammer at 2 meters
is 100 dB. The Krakatoa explosion at 100 miles was 180 dB. A rifle
being fired is 140 dB. OSHA defines dangerous hearing loss at
greater than 85 dB over a normal 40 hour work week. The standards
in other parts of the world are more stringent.
[0017] The Israeli medical association reported that 33 out of 34
of people who survived a suicide terrorist attack on a municipal
bus sustained hearing damage, yet all patients had normal
electronystagmography indicating vestibular function remained
unaffected even in close proximity to the blast. i.e. the bony
encasement of the semicircular canals protected them against the
blast overpressure force while the more vulnerable hearing organs
were uniformly damaged.
[0018] In past, various attempts have been made to provide earplug
or ear protectors. Such past attempts include U.S. Pat. No.
4,807,612 entitled "Passive Ear Protector," U.S. Pat. No. 4,852,683
to "Earplug with Improved Audibility," U.S. Pat. No. 5,113,967
entitled "Audibility Earplug," U.S. Pat. No. 6,070,693 entitled
"Hearing Protector Against Loud Noise," and U.S. Pat. No. 6,148,821
entitled "Selective Nonlinear Attenuating Earplug." While these
past attempts may have provided some attenuation of or protection
against loud noises, they did not provide the protection provided
by the present invention in combination with not substantially
limiting or adversely affecting normal hearing.
SUMMARY OF THE INVENTION
[0019] The present invention prevents hearing damage from occurring
by means of highly engineered ear protection utilizing microdevices
and components, inserted into the ear canal of individuals or worn
as a covering over the outer ear prior to military or industrial
operations. The solutions are based on multidisciplinary
problem-based learning approach to understand the at-risk
anatomical features of the hearing organ, a thorough understanding
of hearing physiology, firsthand medical assessment of soldiers
injured in battle, and engineering application of the most
up-to-date nanotechnology principles and designs. The devices
resulting from the present invention hold no resemblance to hearing
aids, which only filter or amplify selected sounds. Instead, the
devices in accordance with the present invention intercepts high
energy acoustic waves and/or reflect acoustic energy away from the
ear canal, and is transparent to low intensity sound waves for
normal hearing and ambient environments.
[0020] In a preferred embodiment, the present invention is an
apparatus for preventing hearing loss. The apparatus comprises a
body made of a soft compliant material having first and second ends
and a channel or sound-transmitting polymer tube extending
therethrough, an acoustically limp material adjacent one of the
ends of the body with the acoustically limp material having a hole
therein aligned with the channel extending through the body, and
component, a film, disc or other structure covering or sealing the
opening in the acoustically limp material. The film or disc may be
formed of a high-strength polymer material and may be one or more
micrometers in thickness. Rather than having a single channel
extending through the body, a plurality of channels may extend
therethrough and a plurality of corresponding holes may be provided
in the acoustically limp material. The diameter of each hole or
channel may be 1 millimeter, or less. The film, disc or other
structure covers or seals the plurality of holes in the
acoustically limp material. The body may cylindrical in shape or
may have another shape to fit snugly in a human ear canal.
[0021] In another disclosed embodiment, an apparatus for preventing
hearing loss according to the present invention comprises a power
supply, an energy activated sensor, an input device for receiving
sound, an output device for transmitting signals toward an eardrum,
a vacuum tube chamber substantially between the input device and
the output device, and a membrane surrounding at least the input
device, the vacuum tube chamber and the output device. The input
device, the output device, the vacuum tube chamber and the membrane
may form at least part of an assembly that fits within a person's
ear canal. The energy activated sensor may comprise a housing and a
plurality of diodes. Alternatively, the energy activated sensor may
comprise a flexible membrane, a mirrored element connected to the
flexible membrane, an LED, a first diode detector array, a second
diode detector array, and a switch; wherein the LED transmits light
toward the first diode detector array. During a normal operation
the first diode detector array receives light from the LED, thereby
causing the switch to be in a first state. During reception of an
acoustic shock wave, the mirrored element is displaced to a
position in which is deflects light from the LED away from the
first diode detector array and toward the second diode array,
thereby causing the switch to be in a second state.
[0022] In a still another embodiment of the invention, an apparatus
for preventing hearing loss comprises an assembly comprising first
and second reflecting discs, an elastic nanoparticle balloon
between the first and second reflecting discs, the balloon
comprising a membrane filled with nanoparticles and a low viscosity
fluid, wherein the nanoparticles form a disc-like structure when
said balloon is compressed, a membrane surrounding the assembly, an
energy activated sensor, and an energy source for supplying energy
to said assembly and said sensor.
[0023] In a still another preferred embodiment of the invention, an
apparatus for preventing hearing loss comprises a housing having
first and second ends, a length of the housing extending between
the first and second ends, a first plurality of empty microtubes
substantially parallel to the length of the housing, a second
plurality of microtubes substantially parallel to the length of
said housing, wherein each of the second plurality of microtubes is
substantially filled with a stack of discs, wherein each disc
comprises a body, at least one sound aperture, an alignment pad and
a disalignment pad, a first winding around each of said second
plurality of microtubes for causing alignment of the apertures in
the stack of discs in the microtube; and a second winding around
each of the second plurality of microtubes for causing disalignment
of the sound apertures in the stack of discs in the microtube.
[0024] In a still another embodiment of the present invention, an
apparatus for preventing hearing loss comprises a housing, a power
supply, a field coil, an energy-activated switch, and an antenna.
The switch activates the field coil to generate an electromagnetic
field that is directed by the antenna toward a cochlea of an ear
when an acoustic shock wave is received at the switch to
substantially paralyze outer hair cells on the cochlea during the
acoustic shock wave.
[0025] Still other aspects, features, and advantages of the present
invention are readily apparent from the following detailed
description, simply by illustrating a preferable embodiments and
implementations. The present invention is also capable of other and
different embodiments and its several details can be modified in
various obvious respects, all without departing from the spirit and
scope of the present invention. Accordingly, the drawings and
descriptions are to be regarded as illustrative in nature, and not
as restrictive. Additional objects and advantages of the invention
will be set forth in part in the description which follows and in
part will be obvious from the description, or may be learned by
practice of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] For a more complete understanding of the present invention
and the advantages thereof, reference is now made to the following
description and the accompanying drawings, in which:
[0027] FIG. 1(a) is a perspective view of a hearing loss prevention
device in accordance with a preferred embodiment of the present
invention.
[0028] FIG. 1(b) is a side view of the hearing loss prevention
device of FIG. 1(a) in accordance with a preferred embodiment of
the present invention.
[0029] FIG. 2(a) is a perspective view of a hearing loss prevention
device in accordance with an alternative preferred embodiment of
the present invention.
[0030] l FIG. 2(b) is a side view of the hearing loss prevention
device of FIG. 2(a) in accordance with a preferred embodiment of
the present invention.
[0031] FIG. 3 is a diagram of a device constructed in accordance
with a third preferred embodiment of the present invention;
[0032] FIG. 4 is a diagram of an alternate arrangement of the third
embodiment of the present invention;
[0033] FIG. 5(a) is a perspective view of a device in accordance
with a fourth preferred embodiment of the present invention;
[0034] FIG. 5(b) is a side and cross sectional view of a device in
accordance with a fourth preferred embodiment of the present
invention.
[0035] FIGS. 6(a) and (b) are top and side views illustrating the
structure of a compressed silicon membrane filled with
nanoparticles forming a portion of the fourth embodiment of the
invention.
[0036] FIGS. 7(a) and (b) are top and side views illustrating the
second structure of a disc-shape bag filled with nanoparticles
intended to be a sound absorber forming a portion of the fourth
embodiment of the invention.
[0037] FIGS. 7(c) and (d) are diagrams illustrating the operation
of nanoparticles in the fourth preferred embodiment of the present
invention.
[0038] FIG. 8 is a diagram of an alternate arrangement for
placement of a device in accordance with the fourth embodiment of
the present invention adjacent a person's ear.
[0039] FIG. 9 is a diagram of a fifth embodiment of the present
invention;
[0040] FIG. 10 is a diagram of tube in accordance with a fifth
embodiment of the present invention;
[0041] FIG. 11 is a diagram illustrating the structure of discs in
accordance with a fifth embodiment of the present invention.
[0042] FIG. 12 is an example of a perforated nanoparticle with
coating such as magnetizable metal in accordance with the fifth
embodiment of the present invention.
[0043] FIG. 13 is a diagram of a device in accordance with a sixth
preferred embodiment of the present invention.
[0044] FIG. 14 is a diagram illustrating the placement of a device
in accordance with the sixth preferred embodiment of the present
invention.
[0045] FIG. 15 is a diagram of a photonic energy activated switch
in accordance with a preferred embodiment of the invention; and
[0046] FIGS. 16(a) and (b) are diagrams of a sound energy activated
switch in accordance with a preferred embodiment of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] The ear canal is the most vulnerable point of entry into the
hearing organ for damaging sound waves. The human body has already
supplied evidence for the protective nature of bone. The only organ
fully encased in bone is the vestibular system, known to contain
the body's balance and position receptors. Even though the
semicircular canals are only millimeters away from the hearing
organ and have delicate sensory cells similar to the loss of
cochlear balance, perception is seldom an incapacitating injury
after an explosive detonation.
[0048] The balance and position organ (semicircular canal system)
is analogous to the hearing organ in three important ways: (1) both
are encased in bone; (2) balance and hearing organs are within
millimeters of each other; and (3) both have delicate sensory cells
necessary for nerve transmission.
[0049] A first preferred embodiment of a hearing loss prevention
device in accordance with the present invention is described with
reference to FIGS. 1(a) and 1(b). This embodiment also might be
referred to as an acoustic isolator assembly. In FIGS. 1(a)-(b), a
perspective view and a side view of an acoustic isolator assembly
for placement within an ear canal is shown. A body 110 preferably
made of a soft compliant material is provided with a plurality of
channels 130 extending therethrough. Channels may be for example,
sound-transmitting polymer tubes. The body 110 preferably is shaped
to fit into an ear canal. The shape of the body 110 may be, for
example, cylindrical. An acoustically limp material forming a
distinct component layer 120 is connected, secured or attached to
an end of the body 110. The plurality of channels 130 extend
through the acoustically limp material 120. A component appearing
as a film or disc 140, made for example with a high strength
polymer, such as mylar, is placed or secured over an end of the
acoustically limp material 120 to thereby cover or seal the
openings 132 of the channels 130. The film or disc 140 may flat or
contoured and may have a thickness ranging up to approximately ten
micrometers. The film or disc in operation 140 preferably is in
direct contact with the end of the acoustically limp material 120.
Preferably, the film or disc 140 seals the openings 132 of the
channels. The component, film or disc 140 alternatively may be
attached on one side to form a flap that closes in response to high
intensity sound energy. In such alternate embodiments, closure is
passive and results from the physical force of the sound energy,
which acts to push the flap shut, closed or sealed against the
component 120.
[0050] The shock wave intercepting film or disc 140 must
simultaneously satisfy two criteria: It must be sufficiently thin
such that it does not interfere with ambient sound transmission,
and it must be sufficiently strong that it does not rupture when
subject to overpressures of one or two atmospheres. Modeling
efforts indicate that a microns-thick film of one of the
commercially-available high-strength polymers can meet these two
requirements. Specifically, the mass/area of the 10-micron film is
sufficiently low as to have little influence on normal sound
transmission. With adjusted radius it is capable of withstanding
overpressures of 2 (or more) atmospheres. The essential mechanism
of the protection afforded by the film (and ear plug seal) is the
blockage of significant airflow through the ear canal thereby
maintaining pressures at the tympanic film, at levels representing
a small fraction of the outer overpressure, and thus minimizing the
subsequent destructive forces transmitted via the ossicles of the
middle ear to the oval window of the cochlea. Key to understanding
this function is the realization that a doubling of the pressure in
the ear (corresponding to an over pressure of one atmosphere)
requires an approximate doubling of the mass of air in the inner
ear. Thus, if the plug/film system can block the mass flow of air
resulting from a step-function of immediate pressure increase
through the ear canal, without impeding the extraordinarily small
amounts of air flow associated with sound transmission, it can
effectively protect the inner ear against significant
overpressures.
[0051] Three results relevant to selecting the thickness and
properties of the film to cover the sound channel are presented.
First, the result of a one-dimensional analysis of the effect of a
film of mass density, .rho..sub.m, and thickness, t, on the
transmission of sound waves through the film. In this estimate, the
film is taken to be unsupported (see following paragraph for the
effect of the support) and free to oscillate--only its mass impedes
the transmission of waves. Consider incident sound waves in air of
frequency, .omega., and pressure amplitude, p.sub.I, "blocked" by
the film. Let p.sub.T be the pressure amplitude of the waves
transmitted through the film into the air on the other side of the
film. A classical analysis of the relation of the transmitted
pressure amplitude to the incident amplitude gives
p T p I = 1 1 + .omega..rho. m t 2 .rho. air c air ##EQU00001##
where and are the density and speed of sound in air. For polymeric
films (.rho..sub.m.about.10.sup.3 kg/m.sup.3) with thicknesses in
the range of t.about.1-10 .mu.m, the transmitted wave will be
essentially unaltered by the film for frequencies below
.omega..about.10.sup.4 s.sup.-1.
[0052] The above estimate ignores the fact that the film will be
firmly attached around the edge of the channel through the ear
plug. Now consider regard the film as a circular clamped plate of
radius R, corresponding to the radius of the channel. The lowest
vibration frequency of the plate is
.omega. c = 10.21 R 2 E m t 3 12 ( 1 - v m 2 ) ##EQU00002##
where and are the Young's modulus and Poisson's ratio of the film.
For polymeric films of 1 radius and thicknesses on the order of
t.about.10 .mu.m the lowest vibration frequency is on the order of
10.sup.4 s.sup.-1. If R=2 mm, the lowest frequency is reduced by a
factor of four. The implication of the two results outlined above
is that the film will respond quasi-statically to sound waves with
frequency less than 10.sup.3 s.sup.-1.
[0053] The most restrictive constraint on the design is the
requirement that the film not restrict the amplitude of the sound
waves in the channel. The amplitude of the air particle motion,
.delta., in a sound wave is related to the amplitude of the
pressure, p.sub.1, by
.delta. p I = 1 .rho. air c air .omega. ##EQU00003##
When subject to a pressure p.sub.1 a clamped circular film
experiences a deflection, .delta..sub.membrane, given by (based on
a quasi-static estimate, c.f. above)
.delta. membrane p I = 3 ( 1 - v m 2 ) R 4 16 Et 3 ##EQU00004##
[0054] To avoid reduction of sound transmission to the inner ear,
the film deflection should not be significantly less than the
amplitude, .delta., of the particle motion. A film with radius 1 mm
and thickness greater than 10 .mu.m does not meet this requirement,
but a film with thickness 1 .mu.m easily does. A film with
thickness 2 .mu.m is currently considered to be optimum, while a
film of thickness of about 6 .mu.m meets the requirement
sufficiently to provide protection from blast overpressure without
substantially reducing normal hearing. Experimentation with sound
transmission as a function of the film thickness will establish
that the quality of hearing is not significantly reduced by the
film.
[0055] Can a circular polymeric film of thickness of order
t.about.1-10 .mu.m and radius R.about.1 mm block an over-pressure,
.DELTA.p, of an atmosphere or more? Two estimates that show that a
well-selected film material can survive these over-pressures based
on the two most likely failure modes. First, consider shear-off at
the perimeter of the film. Elementary equilibrium requires that the
shear strength, .tau..sub.m, of the film must be such that
.tau. m > R 2 t .DELTA. p ##EQU00005##
[0056] Thin film polymeric materials exist whose shear strength is
adequate (.about.50 MPa) to ensure survival of films even as thin
as 1 .mu.m to survive an over-pressure of an atmosphere (0.1 MPa).
Next, consider tensile tearing of the film at it perimeter. In this
case the tensile strength of the film, .sigma..sub.m, must
satisfy
.sigma. m > R 2 t sin .alpha. .DELTA. p ##EQU00006##
where .alpha. is the deflection angle of the film at the perimeter.
Assuming moderate ductility, a film should be able sustain
deflection angles on the order of .alpha..about.30.degree.. For
this failure mode, as well, there is a selection of thin film
materials that can survive over-pressures of several atmospheres
for thicknesses on the order of 1 .mu.m or more.
[0057] Viscous effects on the propagation of pressure pulses: In
the simplest cases of sound propagation it is sufficient to solve
the wave equation in the geometry of interest. For example, when
amplitudes are small, any arbitrary signal can be represented as a
Fourier series, and each Fourier mode (frequency .omega.)
propagates with the wave (sound) speed c. The wave length of the
propagating signal is then .lamda.=c/.omega..
[0058] Viscous effects in the gas damp the wave propagation. The
effect of viscosity is always present near rigid boundaries since
the no-slip boundary condition demands that the fluid speed tangent
to the surface equals zero at a stationary rigid wall. This viscous
damping is, of course, unwanted if there is only to be limited
sound attenuation (either noise or a spoken command).
[0059] To estimate the viscous effects it is simply necessary to
note that in any oscillatory fluid flow (small amplitude sound
signals correspond to oscillatory fluid motions) there is a narrow
region--a boundary layer--near the rigid surface where viscous
effects are typically confined. The thickness of the layer .delta.
is approximately (.nu./.omega.).sup.1/2, where .nu. is the
kinematic viscosity of the fluid. Consequently, for sound
propagation through a narrow constriction of width W, we should
expect viscous effects to be negligible so long as
.delta.=(.nu./.omega.).sup.1/2<W. For air at room temperature
and pressure, .nu.=10.sup.-5 m.sup.2/sec. For a typical audio
frequency of 1000 Hz, the boundary-layer thickness is about 100
micrometers, which is about the thickness of a human hair.
[0060] A second preferred embodiment of a hearing loss prevention
device in accordance with the present invention is described with
reference to FIGS. 2(a) and (b). This embodiment likewise might be
referred to as an acoustic isolator assembly. In FIGS. 2(a)-(b), a
perspective view and a side view of an acoustic isolator assembly
for placement within an ear canal is shown. A body 210 preferably
made of a soft compliant material is provided with a single channel
230 extending therethrough. The body 210 preferably is shaped to
fit into an ear canal. The shape of the body 210 may be, for
example, cylindrical. An acoustically limp material 220 is
connected, secured or attached to an end of the body 210. The
channel 230 extends through the acoustically limp material 220. A
film or disc 240, made for example with a high strength polymer is
placed or secured over an end of the acoustically limp material 220
to thereby cover or seal the openings 232 of the channels 230. The
film or disc 240 may flat or contoured and may have a thickness
ranging from a few micrometers to several tenths of micrometers.
The film or disc 240 preferably is in direct contact with the end
of the acoustically limp material 220.
[0061] The device in accordance with the present invention will
selectively intercept and reflect shock wave energy into a
direction perpendicular to the ear canal by utilizing a sound-
transmitting tube or tubes 130, 230 with a high-strength film 140,
240 covering the outer opening(s) 132, 232. The tube(s) 130, 230
will be surrounded by high-density, acoustically limp, material
120, 220 and will be inserted into the external auditory canal. The
film 140, 240 will reflect high-energy acoustic waves, but will be
transparent to low intensity sound waves for normal hearing, and
ambient sounds.
[0062] The high-strength polymer film 140, 240, on the order of
several microns in thickness, and capable of reflecting high-energy
acoustic waves, covers one or more small-radius hole(s) 130, 230
designed to allow innocuous sound transmission required for
front-line communication. The assembly will be fully encased in
compliant medical grade silicone 150, 250 and be inserted into the
ear canal at or near the cartilaginous/bony interface.
[0063] In operation, the shock wave intercepting film 140, 240 must
simultaneously satisfy two essential criteria: It must be
sufficiently thin such that it does not interfere with sound
transmission, and it must be sufficiently strong that it does not
rupture when subject to overpressures of one or two atmospheres.
Modeling efforts indicate that a microns thick film of one of the
commercially-available high-strength polymer can meet these two
requirements. Specifically, the mass/area of the 10-micron film is
sufficiently low as to have little influence on sound transmission.
With adjusted radius it is capable of withstanding overpressures of
2 (or more) atmospheres. The essential mechanism of the protection
afforded by the film (and ear plug seal) is the blockage of
significant airflow through the ear canal thereby maintaining
pressures at the tympanic membrane, at levels representing a small
fraction of the outer overpressure, and thus minimize the
subsequent destructive forces transmitted via the ossicles of the
middle ear to the oval window of the cochlea. To appreciate this
effect, one must realize that an overpressure of two atmospheres
would require roughly an instantaneous doubling of the mass of air
within the ear canal region. Thus, if the plug/thin film system can
block the mass flow of air resulting from a step-function of
immediate pressure increase through the ear canal (without impeding
the extraordinarily small amounts of air flow associated with sound
transmission), it can effectively protect the inner ear against
significant overpressures.
[0064] While some of the embodiments of the present invention have
been described in the military context, it should be understood
that all of the embodiments are applicable to many circumstances or
settings other than military settings.
[0065] In a third preferred embodiment of the present invention, a
concept that may be referred to as "vacuum interposition" is
employed. Generally speaking, the embodiment uses hearing
protective technology consisting of silicone rubber-covered sealed
cavities containing micro circuitry adapted from affixed to ends of
a vacuum chamber in the ear canal.
[0066] As shown in FIG. 3, the third preferred embodiment of the
invention has a power supply 310, an energy activated sensor or
switch 320, and a silicon membrane 330 having within it an input
device or receiver 340, a vacuum tube chamber 350, and an output
device or transmitter 360. The energy activated sensor or switch
may be of any of a variety of structure or arrangements, two of
which are discussed below with reference to FIG. 15 and FIGS. 16(a)
and (b). The energy activated sensor has a response time interval,
for example, of less than 30 microseconds. Other response times may
be appropriate and useful under various circumstances and the
present invention is not limited to any particular sensor or switch
or any particular response time.
[0067] The input device 340 has circuitry or other means (not
shown) for conducting or transmitting signals through the device.
The signals may be conducted or transmitted through the device by
any means, for example, by photonic through the vacuum, electrical
wired or RF-energy wired. The output device 360 receives signals
from the input device and transduces sound to the ear drum.
[0068] The device may be designed to transmit sounds in a
particular frequency range. For example, frequencies in the range
(500 to 4,000 Hz) of verbal commands and sounds found in the
immediate surrounding may be transmitted by wired, electromagnetic
or laser transmitted photonic energy through a vacuum chamber to a
receiver adjacent to the ear drum. If electromagnetic broadcast is
utilized, the effective transmission range of transmitter 350 would
be less than 10 cm enabling redundant contralateral hearing should
systems failure occur on one side. The energy activated sensor or
switch 320 will respond to incoming sonic blast(s) and turn off the
sound transmission component of the device. To limit hearing
damage, switch response time will be less than 1 millisecond, with
approximately 30 microseconds attained. Reset time interval will be
less than 30 microseconds. To prevent interception, the transmitter
350 and receiver 330 may be paired using, for example, prime number
encryption. The present invention is not limited to encrypted
signals or any particular type of encrypted signals.
[0069] The embodiment further may have different settings, adjusted
by changing the sensitivity of the device or the sensors for
various circumstances, whether the context be military, industrial
or otherwise. For example, in military settings, three decibel (dB)
tolerance settings could be used: (1) sleeping quarters; (2)
recreational area; and (3) mess hall to accommodate ambient noise.
Fewer or greater tolerance settings may be provided with the
present invention. Operational settings could feature combat mode,
transport mode (trucks, Humvees, helicopters), and quiet
(reconnaissance) mode. An alternate approach for this preferred
embodiment is to use microfabricated quantum cascade lasers to
transmit photonic "sounds" through the vacuum.
[0070] In FIG. 3, the device is shown as being constructed to be
inserted into an ear canal between an ear drum 372 and an ear canal
opening 374. Such a device preferably is designed such that the
silicone membrane 330 fits tight in a typical ear canal. In an
alternate arrangement, a device in accordance with this third
embodiment may be constructed to fit over an ear 380 like an ear
muff. Many other arrangements of this third embodiment of the
invention, such as being part of a head band, helmet, hat, head or
body container or the like are possible and will be apparent to one
of ordinary skill in the art.
[0071] A fourth preferred embodiment will be described with
reference to FIGS. 5-8. Preliminarily, it is known that infants
with ear canal wall atresia with an intact inner ear register a 90
dB hearing loss. Using this knowledge, the fourth embodiment of the
present invention takes advantage of physical properties of
advanced polymer gel chemistries and nanoscale structures to
protect the hearing organ from incoming pressure forces by forming
"instant bone" in the ear canal that simulates an atretic ear.
[0072] The ear canal is the most vulnerable point of entry into the
hearing organ for damaging sound waves. The human body has already
supplied evidence for the protective nature of bone. The only organ
fully encased in bone is the vestibular system, known to contain
the body's balance and position receptors. Even though the
semicircular canals are only millimeters away from the hearing
organ and have delicate sensory cells similar to the loss of
cochlear balance, perception is seldom an incapacitating injury
after an explosive detonation.
[0073] The balance and position organ (semicircular canal system)
is analogous to the hearing organ in three important ways: (1) both
are encased in bone; (2) balance and hearing organs are within
millimeters of each other; and (3) both have delicate sensory cells
necessary for nerve transmission.
[0074] In FIGS. 5(a) and (b), a perspective view and a
cross-section of an acoustic isolator assembly for placement within
an ear canal is shown. A plurality of sound transmitting polymer
tubes 510 run through gel or fluid-filled spacers 515 that are
delimited by paired bi-concave discs 530, 540 interspaced with a
gel with a high spring constant. The gel spacers 515 may have
peripheral grooves on their outer surfaces to give the acoustic
isolator assembly shape filling capacity and some reserve capacity
to fit into an ear snugly upon expansion or activation. Small discs
520 contain nanoparticles 710 and elastic microballoons 720 of a
higher density than the gel in the spacers. The discs 530, 540
preferably are formed from a hard sound reflecting material. The
discs may be shaped, for example, like a snail operculum as shown
in FIGS. 6(a) and (b) and are flat plates, bi-concave,
convex/concave or bi-convex . The acoustic isolator assembly is
covered with a silicone membrane 550
[0075] The acoustic isolator assembly of this fourth embodiment
instantaneously responds to abrupt changes in sonic pressure to
form into a material with bone-like consistency in the ear canal,
closing sound conducting channels 212 in energy ranges from 500 to
10,000 Hz, such as those found in the range of verbal commands and
the immediate operational surroundings. All sounds are transmitted
from the outer ear region to the ear drum through a
gel/nanoparticle matrix. The gel 520 is designed to attenuate the
transmission of energy at levels known to damage the hearing organ.
As shown in FIG. 5, the incoming pressure wave impacts the outer
disc 530 displacing this disc inward toward the ear canal. The pair
of biconcave discs 530, 540 is compressed from the sonic energy
squeezing fluid in the gel spaces 520 into the silicon membrane 552
as shown in FIG. 5. The residual shock energy passes through the
subjacent rubber-like gel spaces 520 to the next biconcave disc
pair 530, 540 compressing into each gel-nanoparticle structure in
sequence until the all complex power levels of sound have been
attenuated. The outer silicone rubber membrane 550 acts as a
reservoir for the displaced fluid and nanoparticles from the inner
cylindrical device. The spring constant of the gel 520 is tuned to
recoil and rebound in less then 30 microseconds. As shown in FIGS.
7(a), 7(b) and 7(d), when the gel spaces 520 are compressed, the
nanoparticles compact together to form a bonelike structure. In
this manner, the gel absorbs energy and the compacted nanoparticles
conduct sound to an angle, orthogonal to the long axis of the ear
canal. Since the fourth embodiment preferably is constructed of
passive components, to energy activation sensor or switch is
necessary, although variations using or requiring such a sensor or
switch will be apparent to those of skill in the art and fall
within the scope of the invention.
[0076] As shown in FIGS. 7(a), 7(b) and 7(d), when the gel spaces
520 are compressed, the nanoparticles compact together to form a
bonelike structure. In this manner, the gel absorbs energy and the
compacted nanoparticles conduct sound to an angle orthogonal to the
long axis of the ear canal. Since the fourth embodiment preferably
is constructed of passive components, to energy activation sensor
or switch is necessary, although variations using or requiring such
a sensor or switch will be apparent to those of skill in the art
and fall within the scope of the invention.
[0077] While the fourth embodiment in shown in FIGS. 5-6 as being a
device that is placed in the ear canal, one of skill in the art
will recognize that many alternatives exist, such as incorporating
the fourth embodiment into an ear muff design such as is shown in
FIG. 8 or another design outside the ear canal.
[0078] A fifth preferred embodiment of the invention is described
with reference to FIGS. 9-12. This fourth preferred embodiment of
the invention selectively reflects acoustic waves by utilizing
nanoparticles with dipole moments that can electromagnetically
re-orient to form acoustic wave deflector surfaces or
nanoperforations.
[0079] As shown in FIG. 9, a cylindrical shaped container 910 with
polymer microtubes 920, 930 running along the long axis of the
container 910 fits within a person's ear canal 370 between the ear
drum 372 and the opening 374. The microtubes 920, 930 are, for
example, on the order of 10 to 100 microns in diameter nm. The
microtubes may be composed of soft and compliant polymer with tiny
ferrous rings or ridges along their circumference. The microtubes
920 are empty to allow ambient sound transmission while the
microtubes 930 are filled with stacked discs 950 as shown in FIGS.
10-11. The unfilled tubes will collapse and close upon sound energy
deformation of the assemblies, or will remain open depending on the
sensitivity and operational mode of the device. Each of the
microtubes 930 is wound with an alignment field coil 922 and a
disalignment field coil 924. Alternatively, the microtubes 930 may
have built into them a conductive series of rings or tracks.
Preferably the discs 950 are made of a material with bone-like
density and sound reflecting and/or absorbing characteristics.
[0080] Each disc 950 has a body 952 with a spindle hole 954 and a
plurality of sound apertures 956 formed within in it, for example,
constructed by microlithography. A short microfabricated column or
wire extends through the spindle holes in the discs in the stack.
Each disc further has a magnetic alignment pad 958 and a magnetic
disalignment pad 960. An intertubular ground substance 970 of
highly elastic, gel encases the microtube array. As with the prior
embodiments of the invention, this embodiment may take on other
forms such as a covering wrapping around the outer aspect of an
ear.
[0081] While FIG. 11 depicts nanodiscs, other types of
nanoparticles such as rods, rectangles, trapezoids, or irregular
discs may be used. For example, the microtubes may be filled with
sound attenuating nanodiscs such as are shown in FIG. 12. The
nanodisc shown in FIG. 12 is made of or coated with sound damping
materials 972 and has a plurality of nanoperforations 974 that are,
for example, 10 nm holes. Alternatively or additionally, the
nanodisc of FIG. 12 may have surface-raised nanobumps. Many
alternatives will apparent to those of ordinary skill in the
art.
[0082] Variations of this embodiment additionally may be used to
produce a protective shield or coating to protect body cavities
from high velocity sound waves traversing beyond the end of travel
for a projectile such as a bullet entrapped by a protective vest.
This layer would be considered a sound aperture beneath the body
armor itself. Activation would be in the form of a switch or local
impact with realignment of the nanoparticles due to magnetic
field.
[0083] A pressure sensitive/shock-wave activated switch turns such
as is shown in FIGS. 15-16 and discussed below turns on EMF
generating coils 980, which in turn align the discs 950 to become
sound deflecting surfaces, re-orienting acoustic energy
perpendicular to the long axis of the ear canal. During reception
of an acoustic shock wave, the filled tubes may be displaced
perpendicular to their length, thereby collapsing or limiting sound
transmission through the empty tubes. The container 910 has three
coils 980 on its circumference, capable of generating up to a 1
tesla Electromagnetic Field. The device will reverse EMF polarity
to disalign the discs. While rotating discs are described in this
embodiment, other designs for nanoparticles such as the following
are possible: split log, cylinder, trapezoid, rhombus, square,
complex rectangles, discoid, oval. A possible drawback of this
preferred embodiment is that it will block some ambient sound even
when not activated.
[0084] A sixth preferred embodiment of the present invention is
based on research showing that outer hair cells can be electrically
stimulated in vitro. Electro stimulatory inhibition of cochlea
sensory cells is used in the sixth preferred embodiment to dampen
sound energy transmitted along the tectoral membrane in the inner
ear. The device will hyperpolarize outer hair cells, attenuates the
mechanical transduction of sound energy onto the tectoral membrane.
The net effect is to render outer hair cells of the cochlea
refractory to sound energy input.
[0085] As shown in FIGS. 13-14, an ear patch 400 affixed to the
skin or outer ear 376 contains a power source 710, a sound
pressure-sensitive switch 720, an electromagnetic field (EMF)
generating coil 730, a light sensor 740 and an antenna 750. The
device may be in the form of an ear patch worn on the outer ear as
is shown in FIGS. 13-14, or may project from the inner aspect of,
for example, a helmet to abut the mastoid region of the skull.
Another design calls for a field coil antenna, inserted into the
ear canal in front of the third, fourth or fifth embodiments of the
present invention to be pointed to the cochlea but not the
vestibular apparatus, the balance and position sensing organ.
[0086] In this sixth embodiment, a pressure sensitive/shock-wave
activated switch turns on EMF generating coils 730, which in turn
hyperpolarize (paralyze) the outer hair sensory cells in the
cochlea, preventing them from activating or transducing sound. It
is known that the protein prestin in the hair cells are contractile
(Anders Fridberger, 2004) which converts receptor potentials into
fast alterations of cellular length and stiffness that routinely
boost hearing sensitivity almost one thousand fold. The device will
stop EMF transmission as the blast shock wave(s) are no longer
encountered.
[0087] In this sixth embodiment, the device will interfere with
hearing until the action potential of the hyperstimulated outer
hair cells return to normal resting state. Alignment of the antenna
is important. The device may use a reflected light signal or the
like to point an EMF antenna 750 to the inferior aspect of the umbo
of the mallius bone of the middle ear.
[0088] FIG. 15 shows an embodiment of a photonic energy activated
switch that may be used in connection with various embodiments of
the present invention. The switch may have a housing 322 and a
plurality 324 of small (approximately 100 microns) light sensing
diodes in the far red to infrared spectrum. The diodes 326 wired in
parallel or in series. The housing 322 may be of any appropriate
shape, form or material to operate with any of the embodiments
discussed above.
[0089] Alternatively, FIGS. 16(a) and (b) illustrate a sound energy
activated switch that may be used in connection with various
embodiments of the present invention. The sound energy activated
switch. FIG. 16(a) illustrates the switch in a position
corresponding to an ON device state 670. FIG. 16(b) illustrates the
switch in a position corresponding to an OFF device state. A
mirrored cone 620 is located in a membrane 610. Two arrays of diode
photodetectors 640 and 650 are arranged perpendicular to each other
with one array 640 aligned with an LED 630 and the other array 640
aligned perpendicular to the LED 630. The LED may, for example, be
approximately 300 microns in diameter. The outputs of the arrays
640 and 650 are connected to a switch 660. The membrane and cone
are aligned relative to the diode arrays and the LED such that
under normal conditions, the mirrored cone 620 does not interfere
with the reception of light from the LED at the array 630, but when
a noise or shock wave displaces the membrane, the mirrored cone
redirects the light from the LED 630 onto array 640, thereby
changing the state of the device from ON to OFF. When the shock
wave dissipates, the membrane and hence the cone return to their
original positions, thereby permitting light form the LED to again
be received by array 630, thereby returning the device to an OFF
state. Tension of the membrane 610 may be adjustable for
sensitivity and different operational modes. Various types of
switches may be used for switch 660 and various arrangements of the
diodes and mirrored cone will be apparent to those of skill in the
art. Additionally, other shapes besides a cone may be used for the
redirection of light and other arrangements of the diodes may be
used.
[0090] While some of the embodiments of the present invention have
been described in the military context, it should be understood
that all of the embodiments are applicable to many circumstances or
settings other than military settings.
[0091] The foregoing description of the preferred embodiment of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed, and modifications and
variations are possible in light of the above teachings or may be
acquired from practice of the invention. The embodiment was chosen
and described in order to explain the principles of the invention
and its practical application to enable one skilled in the art to
utilize the invention in various embodiments as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto, and their
equivalents. The entirety of each of the aforementioned documents
is incorporated by reference herein.
* * * * *