Nano-otologic Protective Equipment For Impact Noise Toxicity And/or Blast Overpressure Exposure Patent Application (2025)

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.

NANO-OTOLOGIC PROTECTIVE EQUIPMENT FOR IMPACT NOISE TOXICITY AND/ORBLAST OVERPRESSURE EXPOSURE

Abstract

An apparatus for preventing hearing loss having a body made of asoft compliant material having first and second ends and a channelextending therethrough, an acoustically limp material adjacent oneof the ends of the body with the acoustically limp material havinga hole therein aligned with the channel extending through the body,and a component film, disc or other structure covering or sealingthe opening in the acoustically limp material. The film or disc maybe formed of a high-strength polymer material and may be less than10 micrometers in thickness. Rather than having a single channelextending through the body, a plurality of channels may extendtherethrough and a plurality of corresponding holes may be providedin the acoustically limp material. The film, disc or otherstructure covers or seals the plurality of holes in theacoustically limp material. The film, disc or other structure maybe attached in such a fashion as to behave like a flap whoseoperation is to close in response to high energy sound waves. Theflap is pressed shut from the high intensity shock wave itself. Thebody may cylindrical in shape or may have another shape to fitsnugly in a human ear canal.

Related U.S. Patent Documents

Claims

1-10. (canceled)

11. An apparatus for preventing hearing loss comprising: a powersupply; an energy activated sensor; an input device for receivingsound; an output device for transmitting signals toward an eardrum;a vacuum tube chamber substantially between said input device andsaid output device; and a membrane surrounding at least said inputdevice, 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 vacuumtube chamber and said membrane form at least part of an assemblythat 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 aplurality 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 thatsaid mirrored element is displaced in a first direction during anacoustic shock wave; an LED; a first diode detector array; a seconddiode detector array; and a switch; wherein said LED transmitslight toward said first diode detector array; during a normaloperation said first diode detector array receives said light fromsaid LED, thereby causing said switch to be in a first states; andduring reception of an acoustic shock wave, said mirrored elementis displaced to a position in which is deflects said light fromsaid LED away from said first diode detector array and toward saidsecond diode array, thereby causing said switch to be in a secondstate.

15. A apparatus for preventing hearing loss comprising: an assemblycomprising: first and second reflecting discs; an elasticnanoparticle balloon between said first and second reflectingdiscs, said balloon comprising a membrane filled with nanoparticlesand a low viscosity fluid, wherein said nanoparticles form adisc-like structure when said balloon is compressed; a membranesurrounding said assembly; an energy activated sensor; and anenergy source for supplying energy to said assembly and saidsensor.

16. A apparatus for preventing hearing loss comprising: an assemblycomprising: first and second pairs of reflecting discs; a first gelspacer between said first pair of reflecting discs; a second gelspacer between said second pair of reflecting discs; an elasticnanoparticle balloon between on of said first pair of reflectingdiscs and one of said second pair of reflecting discs, said ballooncomprising a membrane filled with nanoparticles and a low viscosityfluid, wherein said nanoparticles form a disc-like structure whensaid balloon is compressed; a membrane surrounding said assembly;an energy activated sensor; and an energy source for supplyingenergy to said assembly and said sensor.

17. An apparatus for preventing hearing loss comprising: a housinghaving first and second ends, a length of said housing extendingbetween said first and second ends; a first plurality of emptymicrotubes substantially parallel to said length of said housing; asecond plurality of microtubes substantially parallel to saidlength of said housing, wherein each of said second plurality ofmicrotubes is substantially filled with a stack of discs, whereineach said disc comprises a body, at least one sound aperture, analignment pad and a disalignment pad; a first winding around eachof said second plurality of microtubes for causing alignment ofsaid apertures in said stack of discs in said microtube; and asecond winding around each of said second plurality of microtubefor causing disalignment of said sound apertures in said stack ofdiscs in said microtube.

18. An apparatus for preventing hearing loss comprising: a housing;a power supply; a field coil; an energy-activated switch; and anantenna; wherein said switch activates said field coil to generatean electromagnetic field that is directed by said antenna toward acochlea of an ear when an acoustic shock wave is received at saidswitch to substantially paralyze outer hair cells on said cochleaduring said acoustic shock wave.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of the filing ofU.S. Provisional Patent Application Ser. No. 60/757,673 filed onJan. 10, 2006 by inventors Rick Rogers, Brendan Clifford andOldmixon Eben entitled "Nano-Otologic Protective Equipment forImpact Noise Toxicity and/or Blass Overpressure Exposure" and U.S.Provisional Patent Application Ser. No. 60/747,246, filed on May15, 2006 by inventors Richard Rogers, Brendan Clifford, RobertWestervelt, John Hutchinson, and Howard Stone entitled "SoundAperture Protective Equipment for Impact Noise Toxicity and/orBlass Overpressure Exposure."

[0002] The aforementioned prior application is hereby incorporatedby 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 ofpost-concussive hearing trauma, and more specifically to physicaldevices, designed to be worn in the ear canal or affixed to theouter ear to block extreme shock wave damage to the hearingorgan.

[0006] 2. Brief Description of The Related Art

[0007] There is a need for devices that provide protection fromblast overpressusre as experienced by military personnel on abattlefield. Communication is the single most important asset ofour battlefield forces. Combat elements function as a team and mustbe able to immediately react to unanticipated operationalcontingencies. Instantaneous and uninterrupted communication isfundamentally important and great effort has been made to insureefficient and redundant communication within and among tacticalunits in the field. However, a crucial aspect of this communicationnetwork has been overlooked--blast induced hearing loss. Frontlinetroops injured by explosions currently experience 64% hearing loss,and represent an instantaneous reduction in the immediate effectivein-theater force, affecting the most critical element in the entirechain--the advance-line soldier.

[0008] For over 500 years, national entities have used explosivecharges to wage war. Front line medical assets; improvements insurgical techniques and the creation of Shock Surgical Trauma Teamshave significantly reduced the mortality radius from explosiveimpacts. Use of individual protective gear and body armor mitigatedismemberment and secondary limb damage in range of explosivesallowing prolonged duration of the effective force on thebattlefield. Hearing damage encountered in what we term theotologic disablement zone extending hundreds of meters away fromthe impact area remains an unaddressed component of battlefieldmorbidity and tactical incapacitation.

[0009] In regional proximity to the target, an explosive charge canproduce a high-pressure shock wave with specific physical pressureswhich not only rupture the eardrum, displacing the middle earossicles, but also destroy inner ear sensory cells in the specificfrequency ranges most utilized for interpersonnel communication.This acute hearing loss results from sharp impulse rise in soundwave intensity produced by proximity to battlefield explosions. Thedamage is immediate and irreversible. Soldiers within the otologicdisablement zone often do not exhibit any outward sign of hearingimpairment just after exposure other than being unable to respondto commands. Battlefield management of the effective force assetsbecome secondarily compromised when the disabled team members areunable to respond to commands. This loss of unit cohesion impedesthe attainment of mission objectives. Valuable time is lost as theeffective force adapts to this compromised situation.

[0010] According to the office of the Army Surgeon General, hearingloss in soldiers sustained to blast injuries are running 64%, byfar the highest category of battlefield injuries, resulting insignificant reduction in effective force in the current War AgainstTerrorism. The year 2004 had the highest rate of increase in combatinjuries hearing loss since records began to be kept in the mid20.sup.th century, a period that included for example; WWII, theKorean War, The Vietnam Conflict, the Marine deployment in Lebanon,The Gulf War, and OIF/OEF.

[0011] In the 2005 survey of hearing protector efficacy, underoperational conditions, it was found that all the tested devicesattenuated C-weighted peak level to less than 130 dB, well belowthe sound peaks experienced in explosions encountered in OIF. Inpractice, these devices attenuated noise by only 10-30 dB.

[0012] Proximity to explosion is more important that size. Studieson conventional bomb blasts ranging from 1 to 20 kg of TNTconfirmed that proximity to explosion is more important to the sizeof the charge. At distances greater than 6 meters victims willprobably not have mortal wounds. A SCUD missile explosion inmilitary personnel housing injured the ears of 172 individuals. Ofthe 86 hospitalized, 76% had ear drum perforations. Distances toexplosion were measured and used to construct mathematical model ofestimated wave form. Fifty percent of soldiers will sustain a eardrum perforation at 185 dB (15 PSI).

[0013] Middle ear damage, such as Tympanic membrane perforation isalways an indication of cochlear damage. An important pointrequires consideration. Tympanic membranes can be surgicallyrepaired. However, there are no medical/surgical procedures torepair cochlear damage.

[0014] As in military applications, protection to the hearing organis important in occupational and industrial settings. Impact noisein the industrial sector presents a problem similar to blastoverpressure in the military sector. According to the U.S.Department of Labor, 28.4 per 10,000 workers will have recordablehearing loss.sub..(2004) US Dept Labor. Ten million haveexperienced permanent hearing loss, 30 million are exposed todangerous noise levels daily (NIOSH)

[0015] Industrial Devices such as electronic ear muffs amplifyoutside noise so those with impaired hearing can hear warningbells. The problem is that they transmit noise and directedcommunication with equal intensity making no distinction betweenthe two. Although they do not electronically transmit noise over aset dB range (often set to >85 dB), they are unable to interceptharmful sound energy which continue onto the middle and inner earunabated.

[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 metersis 150 dB. A loud factory is 90 dB. A pneumatic hammer at 2 metersis 100 dB. The Krakatoa explosion at 100 miles was 180 dB. A riflebeing fired is 140 dB. OSHA defines dangerous hearing loss atgreater than 85 dB over a normal 40 hour work week. The standardsin other parts of the world are more stringent.

[0017] The Israeli medical association reported that 33 out of 34of people who survived a suicide terrorist attack on a municipalbus sustained hearing damage, yet all patients had normalelectronystagmography indicating vestibular function remainedunaffected even in close proximity to the blast. i.e. the bonyencasement of the semicircular canals protected them against theblast overpressure force while the more vulnerable hearing organswere uniformly damaged.

[0018] In past, various attempts have been made to provide earplugor ear protectors. Such past attempts include U.S. Pat. No.4,807,612 entitled "Passive Ear Protector," U.S. Pat. No. 4,852,683to "Earplug with Improved Audibility," U.S. Pat. No. 5,113,967entitled "Audibility Earplug," U.S. Pat. No. 6,070,693 entitled"Hearing Protector Against Loud Noise," and U.S. Pat. No. 6,148,821entitled "Selective Nonlinear Attenuating Earplug." While thesepast attempts may have provided some attenuation of or protectionagainst loud noises, they did not provide the protection providedby the present invention in combination with not substantiallylimiting or adversely affecting normal hearing.

SUMMARY OF THE INVENTION

[0019] The present invention prevents hearing damage from occurringby means of highly engineered ear protection utilizing microdevicesand components, inserted into the ear canal of individuals or wornas a covering over the outer ear prior to military or industrialoperations. The solutions are based on multidisciplinaryproblem-based learning approach to understand the at-riskanatomical features of the hearing organ, a thorough understandingof hearing physiology, firsthand medical assessment of soldiersinjured in battle, and engineering application of the mostup-to-date nanotechnology principles and designs. The devicesresulting from the present invention hold no resemblance to hearingaids, which only filter or amplify selected sounds. Instead, thedevices in accordance with the present invention intercepts highenergy acoustic waves and/or reflect acoustic energy away from theear canal, and is transparent to low intensity sound waves fornormal hearing and ambient environments.

[0020] In a preferred embodiment, the present invention is anapparatus for preventing hearing loss. The apparatus comprises abody made of a soft compliant material having first and second endsand a channel or sound-transmitting polymer tube extendingtherethrough, an acoustically limp material adjacent one of theends of the body with the acoustically limp material having a holetherein aligned with the channel extending through the body, andcomponent, a film, disc or other structure covering or sealing theopening in the acoustically limp material. The film or disc may beformed of a high-strength polymer material and may be one or moremicrometers in thickness. Rather than having a single channelextending through the body, a plurality of channels may extendtherethrough and a plurality of corresponding holes may be providedin the acoustically limp material. The diameter of each hole orchannel may be 1 millimeter, or less. The film, disc or otherstructure covers or seals the plurality of holes in theacoustically limp material. The body may cylindrical in shape ormay have another shape to fit snugly in a human ear canal.

[0021] In another disclosed embodiment, an apparatus for preventinghearing loss according to the present invention comprises a powersupply, an energy activated sensor, an input device for receivingsound, an output device for transmitting signals toward an eardrum,a vacuum tube chamber substantially between the input device andthe output device, and a membrane surrounding at least the inputdevice, the vacuum tube chamber and the output device. The inputdevice, the output device, the vacuum tube chamber and the membranemay form at least part of an assembly that fits within a person'sear canal. The energy activated sensor may comprise a housing and aplurality of diodes. Alternatively, the energy activated sensor maycomprise a flexible membrane, a mirrored element connected to theflexible membrane, an LED, a first diode detector array, a seconddiode detector array, and a switch; wherein the LED transmits lighttoward the first diode detector array. During a normal operationthe first diode detector array receives light from the LED, therebycausing the switch to be in a first state. During reception of anacoustic shock wave, the mirrored element is displaced to aposition in which is deflects light from the LED away from thefirst 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 apparatusfor preventing hearing loss comprises an assembly comprising firstand second reflecting discs, an elastic nanoparticle balloonbetween the first and second reflecting discs, the ballooncomprising a membrane filled with nanoparticles and a low viscosityfluid, wherein the nanoparticles form a disc-like structure whensaid balloon is compressed, a membrane surrounding the assembly, anenergy activated sensor, and an energy source for supplying energyto said assembly and said sensor.

[0023] In a still another preferred embodiment of the invention, anapparatus for preventing hearing loss comprises a housing havingfirst and second ends, a length of the housing extending betweenthe first and second ends, a first plurality of empty microtubessubstantially parallel to the length of the housing, a secondplurality of microtubes substantially parallel to the length ofsaid housing, wherein each of the second plurality of microtubes issubstantially filled with a stack of discs, wherein each disccomprises a body, at least one sound aperture, an alignment pad anda disalignment pad, a first winding around each of said secondplurality of microtubes for causing alignment of the apertures inthe stack of discs in the microtube; and a second winding aroundeach of the second plurality of microtubes for causing disalignmentof the sound apertures in the stack of discs in the microtube.

[0024] In a still another embodiment of the present invention, anapparatus for preventing hearing loss comprises a housing, a powersupply, a field coil, an energy-activated switch, and an antenna.The switch activates the field coil to generate an electromagneticfield that is directed by the antenna toward a cochlea of an earwhen an acoustic shock wave is received at the switch tosubstantially paralyze outer hair cells on the cochlea during theacoustic shock wave.

[0025] Still other aspects, features, and advantages of the presentinvention are readily apparent from the following detaileddescription, simply by illustrating a preferable embodiments andimplementations. The present invention is also capable of other anddifferent embodiments and its several details can be modified invarious obvious respects, all without departing from the spirit andscope of the present invention. Accordingly, the drawings anddescriptions are to be regarded as illustrative in nature, and notas restrictive. Additional objects and advantages of the inventionwill be set forth in part in the description which follows and inpart will be obvious from the description, or may be learned bypractice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] For a more complete understanding of the present inventionand the advantages thereof, reference is now made to the followingdescription and the accompanying drawings, in which:

[0027] FIG. 1(a) is a perspective view of a hearing loss preventiondevice in accordance with a preferred embodiment of the presentinvention.

[0028] FIG. 1(b) is a side view of the hearing loss preventiondevice of FIG. 1(a) in accordance with a preferred embodiment ofthe present invention.

[0029] FIG. 2(a) is a perspective view of a hearing loss preventiondevice in accordance with an alternative preferred embodiment ofthe present invention.

[0030] l FIG. 2(b) is a side view of the hearing loss preventiondevice of FIG. 2(a) in accordance with a preferred embodiment ofthe present invention.

[0031] FIG. 3 is a diagram of a device constructed in accordancewith a third preferred embodiment of the present invention;

[0032] FIG. 4 is a diagram of an alternate arrangement of the thirdembodiment of the present invention;

[0033] FIG. 5(a) is a perspective view of a device in accordancewith a fourth preferred embodiment of the present invention;

[0034] FIG. 5(b) is a side and cross sectional view of a device inaccordance with a fourth preferred embodiment of the presentinvention.

[0035] FIGS. 6(a) and (b) are top and side views illustrating thestructure of a compressed silicon membrane filled withnanoparticles forming a portion of the fourth embodiment of theinvention.

[0036] FIGS. 7(a) and (b) are top and side views illustrating thesecond structure of a disc-shape bag filled with nanoparticlesintended to be a sound absorber forming a portion of the fourthembodiment of the invention.

[0037] FIGS. 7(c) and (d) are diagrams illustrating the operationof nanoparticles in the fourth preferred embodiment of the presentinvention.

[0038] FIG. 8 is a diagram of an alternate arrangement forplacement of a device in accordance with the fourth embodiment ofthe present invention adjacent a person's ear.

[0039] FIG. 9 is a diagram of a fifth embodiment of the presentinvention;

[0040] FIG. 10 is a diagram of tube in accordance with a fifthembodiment of the present invention;

[0041] FIG. 11 is a diagram illustrating the structure of discs inaccordance with a fifth embodiment of the present invention.

[0042] FIG. 12 is an example of a perforated nanoparticle withcoating such as magnetizable metal in accordance with the fifthembodiment of the present invention.

[0043] FIG. 13 is a diagram of a device in accordance with a sixthpreferred embodiment of the present invention.

[0044] FIG. 14 is a diagram illustrating the placement of a devicein accordance with the sixth preferred embodiment of the presentinvention.

[0045] FIG. 15 is a diagram of a photonic energy activated switchin accordance with a preferred embodiment of the invention; and

[0046] FIGS. 16(a) and (b) are diagrams of a sound energy activatedswitch in accordance with a preferred embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] The ear canal is the most vulnerable point of entry into thehearing organ for damaging sound waves. The human body has alreadysupplied evidence for the protective nature of bone. The only organfully encased in bone is the vestibular system, known to containthe body's balance and position receptors. Even though thesemicircular canals are only millimeters away from the hearingorgan and have delicate sensory cells similar to the loss ofcochlear balance, perception is seldom an incapacitating injuryafter an explosive detonation.

[0048] The balance and position organ (semicircular canal system)is analogous to the hearing organ in three important ways: (1) bothare encased in bone; (2) balance and hearing organs are withinmillimeters of each other; and (3) both have delicate sensory cellsnecessary for nerve transmission.

[0049] A first preferred embodiment of a hearing loss preventiondevice in accordance with the present invention is described withreference to FIGS. 1(a) and 1(b). This embodiment also might bereferred to as an acoustic isolator assembly. In FIGS. 1(a)-(b), aperspective view and a side view of an acoustic isolator assemblyfor placement within an ear canal is shown. A body 110 preferablymade of a soft compliant material is provided with a plurality ofchannels 130 extending therethrough. Channels may be for example,sound-transmitting polymer tubes. The body 110 preferably is shapedto fit into an ear canal. The shape of the body 110 may be, forexample, cylindrical. An acoustically limp material forming adistinct component layer 120 is connected, secured or attached toan end of the body 110. The plurality of channels 130 extendthrough the acoustically limp material 120. A component appearingas a film or disc 140, made for example with a high strengthpolymer, such as mylar, is placed or secured over an end of theacoustically limp material 120 to thereby cover or seal theopenings 132 of the channels 130. The film or disc 140 may flat orcontoured and may have a thickness ranging up to approximately tenmicrometers. The film or disc in operation 140 preferably is indirect contact with the end of the acoustically limp material 120.Preferably, the film or disc 140 seals the openings 132 of thechannels. The component, film or disc 140 alternatively may beattached on one side to form a flap that closes in response to highintensity sound energy. In such alternate embodiments, closure ispassive and results from the physical force of the sound energy,which acts to push the flap shut, closed or sealed against thecomponent 120.

[0050] The shock wave intercepting film or disc 140 mustsimultaneously satisfy two criteria: It must be sufficiently thinsuch that it does not interfere with ambient sound transmission,and it must be sufficiently strong that it does not rupture whensubject to overpressures of one or two atmospheres. Modelingefforts indicate that a microns-thick film of one of thecommercially-available high-strength polymers can meet these tworequirements. Specifically, the mass/area of the 10-micron film issufficiently low as to have little influence on normal soundtransmission. With adjusted radius it is capable of withstandingoverpressures of 2 (or more) atmospheres. The essential mechanismof the protection afforded by the film (and ear plug seal) is theblockage of significant airflow through the ear canal therebymaintaining pressures at the tympanic film, at levels representinga small fraction of the outer overpressure, and thus minimizing thesubsequent destructive forces transmitted via the ossicles of themiddle ear to the oval window of the cochlea. Key to understandingthis function is the realization that a doubling of the pressure inthe ear (corresponding to an over pressure of one atmosphere)requires an approximate doubling of the mass of air in the innerear. Thus, if the plug/film system can block the mass flow of airresulting from a step-function of immediate pressure increasethrough the ear canal, without impeding the extraordinarily smallamounts of air flow associated with sound transmission, it caneffectively protect the inner ear against significantoverpressures.

[0051] Three results relevant to selecting the thickness andproperties of the film to cover the sound channel are presented.First, the result of a one-dimensional analysis of the effect of afilm of mass density, .rho..sub.m, and thickness, t, on thetransmission of sound waves through the film. In this estimate, thefilm is taken to be unsupported (see following paragraph for theeffect of the support) and free to oscillate--only its mass impedesthe transmission of waves. Consider incident sound waves in air offrequency, .omega., and pressure amplitude, p.sub.I, "blocked" bythe film. Let p.sub.T be the pressure amplitude of the wavestransmitted through the film into the air on the other side of thefilm. A classical analysis of the relation of the transmittedpressure 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 polymericfilms (.rho..sub.m.about.10.sup.3 kg/m.sup.3) with thicknesses inthe range of t.about.1-10 .mu.m, the transmitted wave will beessentially 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 befirmly attached around the edge of the channel through the earplug. Now consider regard the film as a circular clamped plate ofradius R, corresponding to the radius of the channel. The lowestvibration 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 oft.about.10 .mu.m the lowest vibration frequency is on the order of10.sup.4 s.sup.-1. If R=2 mm, the lowest frequency is reduced by afactor of four. The implication of the two results outlined aboveis that the film will respond quasi-statically to sound waves withfrequency less than 10.sup.3 s.sup.-1.

[0053] The most restrictive constraint on the design is therequirement that the film not restrict the amplitude of the soundwaves in the channel. The amplitude of the air particle motion,.delta., in a sound wave is related to the amplitude of thepressure, 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 filmexperiences a deflection, .delta..sub.membrane, given by (based ona 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 theamplitude, .delta., of the particle motion. A film with radius 1 mmand thickness greater than 10 .mu.m does not meet this requirement,but a film with thickness 1 .mu.m easily does. A film withthickness 2 .mu.m is currently considered to be optimum, while afilm of thickness of about 6 .mu.m meets the requirementsufficiently to provide protection from blast overpressure withoutsubstantially reducing normal hearing. Experimentation with soundtransmission as a function of the film thickness will establishthat the quality of hearing is not significantly reduced by thefilm.

[0055] Can a circular polymeric film of thickness of ordert.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 awell-selected film material can survive these over-pressures basedon the two most likely failure modes. First, consider shear-off atthe perimeter of the film. Elementary equilibrium requires that theshear 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 isadequate (.about.50 MPa) to ensure survival of films even as thinas 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 thiscase the tensile strength of the film, .sigma..sub.m, mustsatisfy

.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 sustaindeflection angles on the order of .alpha..about.30.degree.. Forthis failure mode, as well, there is a selection of thin filmmaterials that can survive over-pressures of several atmospheresfor thicknesses on the order of 1 .mu.m or more.

[0057] Viscous effects on the propagation of pressure pulses: Inthe simplest cases of sound propagation it is sufficient to solvethe wave equation in the geometry of interest. For example, whenamplitudes are small, any arbitrary signal can be represented as aFourier series, and each Fourier mode (frequency .omega.)propagates with the wave (sound) speed c. The wave length of thepropagating signal is then .lamda.=c/.omega..

[0058] Viscous effects in the gas damp the wave propagation. Theeffect of viscosity is always present near rigid boundaries sincethe no-slip boundary condition demands that the fluid speed tangentto the surface equals zero at a stationary rigid wall. This viscousdamping is, of course, unwanted if there is only to be limitedsound attenuation (either noise or a spoken command).

[0059] To estimate the viscous effects it is simply necessary tonote that in any oscillatory fluid flow (small amplitude soundsignals correspond to oscillatory fluid motions) there is a narrowregion--a boundary layer--near the rigid surface where viscouseffects are typically confined. The thickness of the layer .delta.is approximately (.nu./.omega.).sup.1/2, where .nu. is thekinematic viscosity of the fluid. Consequently, for soundpropagation through a narrow constriction of width W, we shouldexpect viscous effects to be negligible so long as.delta.=(.nu./.omega.).sup.1/2<W. For air at room temperatureand pressure, .nu.=10.sup.-5 m.sup.2/sec. For a typical audiofrequency of 1000 Hz, the boundary-layer thickness is about 100micrometers, which is about the thickness of a human hair.

[0060] A second preferred embodiment of a hearing loss preventiondevice in accordance with the present invention is described withreference to FIGS. 2(a) and (b). This embodiment likewise might bereferred to as an acoustic isolator assembly. In FIGS. 2(a)-(b), aperspective view and a side view of an acoustic isolator assemblyfor placement within an ear canal is shown. A body 210 preferablymade of a soft compliant material is provided with a single channel230 extending therethrough. The body 210 preferably is shaped tofit into an ear canal. The shape of the body 210 may be, forexample, cylindrical. An acoustically limp material 220 isconnected, secured or attached to an end of the body 210. Thechannel 230 extends through the acoustically limp material 220. Afilm or disc 240, made for example with a high strength polymer isplaced or secured over an end of the acoustically limp material 220to thereby cover or seal the openings 232 of the channels 230. Thefilm or disc 240 may flat or contoured and may have a thicknessranging from a few micrometers to several tenths of micrometers.The film or disc 240 preferably is in direct contact with the endof the acoustically limp material 220.

[0061] The device in accordance with the present invention willselectively intercept and reflect shock wave energy into adirection 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, 230will be surrounded by high-density, acoustically limp, material120, 220 and will be inserted into the external auditory canal. Thefilm 140, 240 will reflect high-energy acoustic waves, but will betransparent to low intensity sound waves for normal hearing, andambient sounds.

[0062] The high-strength polymer film 140, 240, on the order ofseveral microns in thickness, and capable of reflecting high-energyacoustic waves, covers one or more small-radius hole(s) 130, 230designed to allow innocuous sound transmission required forfront-line communication. The assembly will be fully encased incompliant medical grade silicone 150, 250 and be inserted into theear canal at or near the cartilaginous/bony interface.

[0063] In operation, the shock wave intercepting film 140, 240 mustsimultaneously satisfy two essential criteria: It must besufficiently thin such that it does not interfere with soundtransmission, and it must be sufficiently strong that it does notrupture when subject to overpressures of one or two atmospheres.Modeling efforts indicate that a microns thick film of one of thecommercially-available high-strength polymer can meet these tworequirements. Specifically, the mass/area of the 10-micron film issufficiently low as to have little influence on sound transmission.With adjusted radius it is capable of withstanding overpressures of2 (or more) atmospheres. The essential mechanism of the protectionafforded by the film (and ear plug seal) is the blockage ofsignificant airflow through the ear canal thereby maintainingpressures at the tympanic membrane, at levels representing a smallfraction of the outer overpressure, and thus minimize thesubsequent destructive forces transmitted via the ossicles of themiddle ear to the oval window of the cochlea. To appreciate thiseffect, one must realize that an overpressure of two atmosphereswould require roughly an instantaneous doubling of the mass of airwithin the ear canal region. Thus, if the plug/thin film system canblock the mass flow of air resulting from a step-function ofimmediate pressure increase through the ear canal (without impedingthe extraordinarily small amounts of air flow associated with soundtransmission), it can effectively protect the inner ear againstsignificant overpressures.

[0064] While some of the embodiments of the present invention havebeen described in the military context, it should be understoodthat all of the embodiments are applicable to many circumstances orsettings other than military settings.

[0065] In a third preferred embodiment of the present invention, aconcept that may be referred to as "vacuum interposition" isemployed. Generally speaking, the embodiment uses hearingprotective technology consisting of silicone rubber-covered sealedcavities containing micro circuitry adapted from affixed to ends ofa vacuum chamber in the ear canal.

[0066] As shown in FIG. 3, the third preferred embodiment of theinvention has a power supply 310, an energy activated sensor orswitch 320, and a silicon membrane 330 having within it an inputdevice or receiver 340, a vacuum tube chamber 350, and an outputdevice or transmitter 360. The energy activated sensor or switchmay be of any of a variety of structure or arrangements, two ofwhich 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 maybe appropriate and useful under various circumstances and thepresent invention is not limited to any particular sensor or switchor any particular response time.

[0067] The input device 340 has circuitry or other means (notshown) for conducting or transmitting signals through the device.The signals may be conducted or transmitted through the device byany means, for example, by photonic through the vacuum, electricalwired or RF-energy wired. The output device 360 receives signalsfrom the input device and transduces sound to the ear drum.

[0068] The device may be designed to transmit sounds in aparticular frequency range. For example, frequencies in the range(500 to 4,000 Hz) of verbal commands and sounds found in theimmediate surrounding may be transmitted by wired, electromagneticor laser transmitted photonic energy through a vacuum chamber to areceiver adjacent to the ear drum. If electromagnetic broadcast isutilized, the effective transmission range of transmitter 350 wouldbe less than 10 cm enabling redundant contralateral hearing shouldsystems failure occur on one side. The energy activated sensor orswitch 320 will respond to incoming sonic blast(s) and turn off thesound transmission component of the device. To limit hearingdamage, switch response time will be less than 1 millisecond, withapproximately 30 microseconds attained. Reset time interval will beless than 30 microseconds. To prevent interception, the transmitter350 and receiver 330 may be paired using, for example, prime numberencryption. The present invention is not limited to encryptedsignals or any particular type of encrypted signals.

[0069] The embodiment further may have different settings, adjustedby changing the sensitivity of the device or the sensors forvarious circumstances, whether the context be military, industrialor 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 thepresent invention. Operational settings could feature combat mode,transport mode (trucks, Humvees, helicopters), and quiet(reconnaissance) mode. An alternate approach for this preferredembodiment is to use microfabricated quantum cascade lasers totransmit photonic "sounds" through the vacuum.

[0070] In FIG. 3, the device is shown as being constructed to beinserted into an ear canal between an ear drum 372 and an ear canalopening 374. Such a device preferably is designed such that thesilicone membrane 330 fits tight in a typical ear canal. In analternate arrangement, a device in accordance with this thirdembodiment may be constructed to fit over an ear 380 like an earmuff. Many other arrangements of this third embodiment of theinvention, such as being part of a head band, helmet, hat, head orbody container or the like are possible and will be apparent to oneof ordinary skill in the art.

[0071] A fourth preferred embodiment will be described withreference to FIGS. 5-8. Preliminarily, it is known that infantswith ear canal wall atresia with an intact inner ear register a 90dB hearing loss. Using this knowledge, the fourth embodiment of thepresent invention takes advantage of physical properties ofadvanced polymer gel chemistries and nanoscale structures toprotect 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 thehearing organ for damaging sound waves. The human body has alreadysupplied evidence for the protective nature of bone. The only organfully encased in bone is the vestibular system, known to containthe body's balance and position receptors. Even though thesemicircular canals are only millimeters away from the hearingorgan and have delicate sensory cells similar to the loss ofcochlear balance, perception is seldom an incapacitating injuryafter an explosive detonation.

[0073] The balance and position organ (semicircular canal system)is analogous to the hearing organ in three important ways: (1) bothare encased in bone; (2) balance and hearing organs are withinmillimeters of each other; and (3) both have delicate sensory cellsnecessary for nerve transmission.

[0074] In FIGS. 5(a) and (b), a perspective view and across-section of an acoustic isolator assembly for placement withinan ear canal is shown. A plurality of sound transmitting polymertubes 510 run through gel or fluid-filled spacers 515 that aredelimited by paired bi-concave discs 530, 540 interspaced with agel with a high spring constant. The gel spacers 515 may haveperipheral grooves on their outer surfaces to give the acousticisolator assembly shape filling capacity and some reserve capacityto fit into an ear snugly upon expansion or activation. Small discs520 contain nanoparticles 710 and elastic microballoons 720 of ahigher density than the gel in the spacers. The discs 530, 540preferably are formed from a hard sound reflecting material. Thediscs may be shaped, for example, like a snail operculum as shownin FIGS. 6(a) and (b) and are flat plates, bi-concave,convex/concave or bi-convex . The acoustic isolator assembly iscovered with a silicone membrane 550

[0075] The acoustic isolator assembly of this fourth embodimentinstantaneously responds to abrupt changes in sonic pressure toform into a material with bone-like consistency in the ear canal,closing sound conducting channels 212 in energy ranges from 500 to10,000 Hz, such as those found in the range of verbal commands andthe immediate operational surroundings. All sounds are transmittedfrom the outer ear region to the ear drum through agel/nanoparticle matrix. The gel 520 is designed to attenuate thetransmission of energy at levels known to damage the hearing organ.As shown in FIG. 5, the incoming pressure wave impacts the outerdisc 530 displacing this disc inward toward the ear canal. The pairof biconcave discs 530, 540 is compressed from the sonic energysqueezing fluid in the gel spaces 520 into the silicon membrane 552as shown in FIG. 5. The residual shock energy passes through thesubjacent rubber-like gel spaces 520 to the next biconcave discpair 530, 540 compressing into each gel-nanoparticle structure insequence until the all complex power levels of sound have beenattenuated. The outer silicone rubber membrane 550 acts as areservoir for the displaced fluid and nanoparticles from the innercylindrical device. The spring constant of the gel 520 is tuned torecoil 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, thenanoparticles compact together to form a bonelike structure. Inthis manner, the gel absorbs energy and the compacted nanoparticlesconduct sound to an angle, orthogonal to the long axis of the earcanal. Since the fourth embodiment preferably is constructed ofpassive components, to energy activation sensor or switch isnecessary, although variations using or requiring such a sensor orswitch will be apparent to those of skill in the art and fallwithin the scope of the invention.

[0076] As shown in FIGS. 7(a), 7(b) and 7(d), when the gel spaces520 are compressed, the nanoparticles compact together to form abonelike structure. In this manner, the gel absorbs energy and thecompacted nanoparticles conduct sound to an angle orthogonal to thelong axis of the ear canal. Since the fourth embodiment preferablyis constructed of passive components, to energy activation sensoror switch is necessary, although variations using or requiring sucha sensor or switch will be apparent to those of skill in the artand fall within the scope of the invention.

[0077] While the fourth embodiment in shown in FIGS. 5-6 as being adevice that is placed in the ear canal, one of skill in the artwill recognize that many alternatives exist, such as incorporatingthe fourth embodiment into an ear muff design such as is shown inFIG. 8 or another design outside the ear canal.

[0078] A fifth preferred embodiment of the invention is describedwith reference to FIGS. 9-12. This fourth preferred embodiment ofthe invention selectively reflects acoustic waves by utilizingnanoparticles with dipole moments that can electromagneticallyre-orient to form acoustic wave deflector surfaces ornanoperforations.

[0079] As shown in FIG. 9, a cylindrical shaped container 910 withpolymer microtubes 920, 930 running along the long axis of thecontainer 910 fits within a person's ear canal 370 between the eardrum 372 and the opening 374. The microtubes 920, 930 are, forexample, on the order of 10 to 100 microns in diameter nm. Themicrotubes may be composed of soft and compliant polymer with tinyferrous rings or ridges along their circumference. The microtubes920 are empty to allow ambient sound transmission while themicrotubes 930 are filled with stacked discs 950 as shown in FIGS.10-11. The unfilled tubes will collapse and close upon sound energydeformation of the assemblies, or will remain open depending on thesensitivity and operational mode of the device. Each of themicrotubes 930 is wound with an alignment field coil 922 and adisalignment field coil 924. Alternatively, the microtubes 930 mayhave built into them a conductive series of rings or tracks.Preferably the discs 950 are made of a material with bone-likedensity and sound reflecting and/or absorbing characteristics.

[0080] Each disc 950 has a body 952 with a spindle hole 954 and aplurality of sound apertures 956 formed within in it, for example,constructed by microlithography. A short microfabricated column orwire extends through the spindle holes in the discs in the stack.Each disc further has a magnetic alignment pad 958 and a magneticdisalignment pad 960. An intertubular ground substance 970 ofhighly elastic, gel encases the microtube array. As with the priorembodiments of the invention, this embodiment may take on otherforms such as a covering wrapping around the outer aspect of anear.

[0081] While FIG. 11 depicts nanodiscs, other types ofnanoparticles such as rods, rectangles, trapezoids, or irregulardiscs may be used. For example, the microtubes may be filled withsound attenuating nanodiscs such as are shown in FIG. 12. Thenanodisc shown in FIG. 12 is made of or coated with sound dampingmaterials 972 and has a plurality of nanoperforations 974 that are,for example, 10 nm holes. Alternatively or additionally, thenanodisc of FIG. 12 may have surface-raised nanobumps. Manyalternatives will apparent to those of ordinary skill in theart.

[0082] Variations of this embodiment additionally may be used toproduce a protective shield or coating to protect body cavitiesfrom high velocity sound waves traversing beyond the end of travelfor a projectile such as a bullet entrapped by a protective vest.This layer would be considered a sound aperture beneath the bodyarmor itself. Activation would be in the form of a switch or localimpact with realignment of the nanoparticles due to magneticfield.

[0083] A pressure sensitive/shock-wave activated switch turns suchas is shown in FIGS. 15-16 and discussed below turns on EMFgenerating coils 980, which in turn align the discs 950 to becomesound deflecting surfaces, re-orienting acoustic energyperpendicular to the long axis of the ear canal. During receptionof an acoustic shock wave, the filled tubes may be displacedperpendicular to their length, thereby collapsing or limiting soundtransmission through the empty tubes. The container 910 has threecoils 980 on its circumference, capable of generating up to a 1tesla Electromagnetic Field. The device will reverse EMF polarityto disalign the discs. While rotating discs are described in thisembodiment, other designs for nanoparticles such as the followingare possible: split log, cylinder, trapezoid, rhombus, square,complex rectangles, discoid, oval. A possible drawback of thispreferred embodiment is that it will block some ambient sound evenwhen not activated.

[0084] A sixth preferred embodiment of the present invention isbased on research showing that outer hair cells can be electricallystimulated in vitro. Electro stimulatory inhibition of cochleasensory cells is used in the sixth preferred embodiment to dampensound energy transmitted along the tectoral membrane in the innerear. The device will hyperpolarize outer hair cells, attenuates themechanical transduction of sound energy onto the tectoral membrane.The net effect is to render outer hair cells of the cochlearefractory to sound energy input.

[0085] As shown in FIGS. 13-14, an ear patch 400 affixed to theskin or outer ear 376 contains a power source 710, a soundpressure-sensitive switch 720, an electromagnetic field (EMF)generating coil 730, a light sensor 740 and an antenna 750. Thedevice may be in the form of an ear patch worn on the outer ear asis 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 theear canal in front of the third, fourth or fifth embodiments of thepresent invention to be pointed to the cochlea but not thevestibular apparatus, the balance and position sensing organ.

[0086] In this sixth embodiment, a pressure sensitive/shock-waveactivated switch turns on EMF generating coils 730, which in turnhyperpolarize (paralyze) the outer hair sensory cells in thecochlea, preventing them from activating or transducing sound. Itis known that the protein prestin in the hair cells are contractile(Anders Fridberger, 2004) which converts receptor potentials intofast alterations of cellular length and stiffness that routinelyboost hearing sensitivity almost one thousand fold. The device willstop EMF transmission as the blast shock wave(s) are no longerencountered.

[0087] In this sixth embodiment, the device will interfere withhearing until the action potential of the hyperstimulated outerhair cells return to normal resting state. Alignment of the antennais important. The device may use a reflected light signal or thelike to point an EMF antenna 750 to the inferior aspect of the umboof the mallius bone of the middle ear.

[0088] FIG. 15 shows an embodiment of a photonic energy activatedswitch that may be used in connection with various embodiments ofthe present invention. The switch may have a housing 322 and aplurality 324 of small (approximately 100 microns) light sensingdiodes in the far red to infrared spectrum. The diodes 326 wired inparallel or in series. The housing 322 may be of any appropriateshape, form or material to operate with any of the embodimentsdiscussed above.

[0089] Alternatively, FIGS. 16(a) and (b) illustrate a sound energyactivated switch that may be used in connection with variousembodiments of the present invention. The sound energy activatedswitch. FIG. 16(a) illustrates the switch in a positioncorresponding to an ON device state 670. FIG. 16(b) illustrates theswitch in a position corresponding to an OFF device state. Amirrored cone 620 is located in a membrane 610. Two arrays of diodephotodetectors 640 and 650 are arranged perpendicular to each otherwith one array 640 aligned with an LED 630 and the other array 640aligned perpendicular to the LED 630. The LED may, for example, beapproximately 300 microns in diameter. The outputs of the arrays640 and 650 are connected to a switch 660. The membrane and coneare aligned relative to the diode arrays and the LED such thatunder normal conditions, the mirrored cone 620 does not interferewith the reception of light from the LED at the array 630, but whena noise or shock wave displaces the membrane, the mirrored coneredirects the light from the LED 630 onto array 640, therebychanging the state of the device from ON to OFF. When the shockwave dissipates, the membrane and hence the cone return to theiroriginal positions, thereby permitting light form the LED to againbe received by array 630, thereby returning the device to an OFFstate. Tension of the membrane 610 may be adjustable forsensitivity and different operational modes. Various types ofswitches may be used for switch 660 and various arrangements of thediodes and mirrored cone will be apparent to those of skill in theart. Additionally, other shapes besides a cone may be used for theredirection of light and other arrangements of the diodes may beused.

[0090] While some of the embodiments of the present invention havebeen described in the military context, it should be understoodthat all of the embodiments are applicable to many circumstances orsettings other than military settings.

[0091] The foregoing description of the preferred embodiment of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and modifications andvariations are possible in light of the above teachings or may beacquired from practice of the invention. The embodiment was chosenand described in order to explain the principles of the inventionand its practical application to enable one skilled in the art toutilize the invention in various embodiments as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto, and theirequivalents. The entirety of each of the aforementioned documentsis incorporated by reference herein.

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