United States Patent
`(12)
`Richardson et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,169,813 B1
`Jan. 2, 2001
`
`US006169813B1
`
`(54) FREQUENCY TRANSPOSITIONAL HEARING
`AH) WITH SINGLE SIDEBANI)
`MODULATION
`
`3,563,246 * 2/1971 Puharich etal. ..................... .. 607/55
`4,156,116 * 5/1979 Yanick ...... ..
`. 381/682
`4,419,544 * 12/1983 Adelman ..
`. 381/682
`
`4,686,705 * 8/1987 Smith . . . . . . . . . . . . . .
`
`. . . .. 455/109
`
`
`
`Inventors: Charles SI Richardson; Arnold SI Llppa, both of Tucson, AZ (US)
`
`
`
`* * Cited by examiner
`
`Lenhardt Ct 8.1.
`
`................. ..
`
`(73) Assignee: Hearing Innovations Incorporated,
`Tucson, AZ (Us)
`
`( * ) Notice:
`
`Under 35 USC. 154(b), the term of this
`patent shall be extended for 0 days.
`
`(21) Appl. N0.: 08/212,571
`_
`_
`Mar‘ 16’ 1994
`(22) Flled'
`(51) Int. Cl.7 ................................................... .. H04R 25/00
`(52) us CL
`381/312. 381/316, 381/320
`(58) Field of
`’
`381/68 2 68 4
`~~~~~~~~~~~~ "
`316
`32'1’
`381
`315 326 ’607/'5’6 5'5 ’57_ 455 /1b9_ 6’00/25’
`’
`’
`’
`’
`’
`’
`References Cited
`
`(56)
`
`U.S. PATENT DOCUMENTS
`
`Primary Examiner—Huyen Le
`(74) Attorney, Agent, or Firm—RothWell, Figg, Ernst &
`Manbeck
`(57)
`
`ABSTRACT
`
`A hearing aid apparatus and method of the type in Which
`audio frequency signals are frequency upshifted to ultra
`sonic frequency bands and are applied as vibrations to the
`human body to generate a hearing response- Frequency
`upshifting of the audio frequency signals to the ultrasonic
`frequency band is attained in one embodiment by amplitude
`modulation of an ultrasonic frequency carrier signal With an
`audio frequency modulating signal to form a modulated
`signal in Which one of the tWo sidebands is either completely
`or substantially suppressed and a modulated signal having
`only one predominant sideband is thus derived for applica
`tion to the human sensory system to generate a hearing
`
`2,995,633 * 8/1961 Puharich et a1. .................. .. 381/68.3
`3,170,993 * 2/1965 Puharich et a1.
`.. 381/683
`3,393,279 * 7/1968 Flanagan .............................. .. 607/56
`
`response‘
`
`11 Claims, 3 Drawing Sheets
`
`14
`CARRIER ,_/
`GENERATOR
`
`11
`a
`
`1O
`
`TRANSDUCER
`
`a
`12
`
`15
`’ ‘”
`16
`1 /
`355
`MODULATOR
`
`2
`17
`
`18
`/
`TRANSDUCER
`
`BODY 21
`
`2 — APPLICATOR
`19
`K
`20
`
`Ex. 2014
`TCL v. Ericsson
`Page 1 of 8
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`U.S. Patent
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`Jan. 2, 2001
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`US 6,169,813 B1
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`U.S. Patent
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`Jan. 2, 2001
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`US 6,169,813 B1
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`U.S. Patent
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`Jan. 2, 2001
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`Sheet 3 013
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`US 6,169,813 B1
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`US 6,169,813 B1
`
`1
`FREQUENCY TRANSPOSITIONAL HEARING
`AID WITH SINGLE SIDEBAND
`MODULATION
`
`The present invention relates to hearing aids for the deaf
`and the hearing impaired and, in particular, to a hearing aid
`apparatus and method Which utilize frequency transposition
`of signals from the audio frequency range to another fre
`quency range, such as the ultrasonic frequency range, and
`vibratory transmission to the human sensory system of the
`frequency shifted signals as a means of communicating With
`the human sensory system.
`
`BACKGROUND AND PRIOR ART
`
`A hearing aid system of one general type to Which the
`present invention relates is disclosed in US. Pat. No.
`4,982,434—Lenhardt et al. In the referenced patent, there is
`disclosed a hearing aid system Which utiliZes such shifting
`of signals from the audio frequency range to the ultrasonic
`frequency range (referred to as “supersonic” frequency
`range in the referenced patent) and bone conduction of the
`ultrasonically shifted signals for communication With the
`human sensory system. In one embodiment of the invention
`as disclosed in the referenced patent, an audio frequency
`signal is amplitude modulated onto an ultrasonic carrier for
`bone conduction transmission. In that embodiment, ampli
`tude modulation is carried out by utiliZing the analog audio
`signal as the modulating signal to modulate an analog
`ultrasonic carrier signal. In such a modulation system as
`disclosed in the referenced patent, an amplitude modulated
`signal With double (upper and loWer) sidebands is derived.
`The referenced system has provided eXcellent results in
`permitting the severely hearing impaired and even otherWise
`totally deaf persons to sense and understand audio frequency
`communications Which have been frequency upshifted to the
`ultrasonic frequency range. It is an object of the present
`invention to provide even further improvements in systems
`of the aforementioned type.
`
`SUMMARY OF THE INVENTION
`The present invention provides further improvements in
`systems of the aforementioned type by providing an appa
`ratus and method in Which amplitude modulation of an
`ultrasonic frequency carrier signal is attained With an audio
`frequency modulating signal and in Which one of the tWo
`sidebands is either completely or substantially suppressed
`and a modulated signal having only one predominant side
`band is derived for application to the human sensory system.
`As Will be more fully explained beloW, it has been discov
`ered that the physiology of the human sensory system is
`more responsive to a an amplitude modulated frequency
`upshifted signal having only a single predominant sideband
`than to a double sideband amplitude modulated signal. The
`apparatus and method of the present invention provide such
`a single sideband amplitude modulated ultrasonic signal in
`a hearing aid apparatus. In one embodiment of the present
`invention Where the loWer sideband Was suppressed and
`only the upper sideband Was utiliZed, signi?cant improve
`ments in hearing response performance Were realiZed.
`Other objects and advantages of the present invention Will
`be apparent from the detailed description Which folloWs,
`taken in connection With the accompanying draWings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram of one embodiment of the
`system of the present invention;
`
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`FIG. 2 is a block diagram of another embodiment of the
`present invention Which includes a signal processor in Which
`the audio frequency signal is processed in various Ways as
`it is upshifted in frequency to an ultrasonic frequency;
`FIG. 2(a) is a cross sectional vieW of a combination
`transducer/applicator utiliZing a pieZoelectric element for
`use in the present invention;
`FIG. 3 is a block diagram of a single sideband amplitude
`modulating circuit suitable for operation in the embodiments
`of FIG. 1 and FIG. 2;
`FIG. 4 is a block diagram of another embodiment of the
`present invention in Which one of the sidebands is sup
`pressed by means of a sideband ?lter; and
`FIG. 5 is an illustration of a dual element hearing aid
`assembly Which includes means for sensing and applying
`frequency upshifted signals to both sides of the head of a
`user.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`In the present invention, a hearing response to audio
`frequency signals is generated using an ultrasonic frequency
`carrier signal Which is amplitude modulated With the audio
`frequency signals With one sideband of the modulated signal
`being suppressed to form a predominantly single sideband
`amplitude modulated signal. The single sideband amplitude
`modulated signal is applied in vibratory form to a portion of
`the human body, such as a portion of the head of a subject,
`to generate a hearing response. As pointed out above, it has
`been discovered that an amplitude modulated ultrasonic
`frequency signal having only one predominant sideband is
`more effective in this type of hearing aid apparatus than a
`double sideband signal of the prior art.
`Referring noW to FIG. 1, there is shoWn a system block
`diagram of one embodiment of the present invention in
`Which a predominantly single sideband modulated ultra
`sonic frequency signal of the aforementioned type is formed
`and applied to the human body to enable hearing perception.
`In this embodiment, a transducer 10 transposes an audio
`airborne signal 11, such as a voice signal, into an electrical
`signal 12. The audio signal 11 may also, of course, be any
`audio frequency signal such as information of any kind
`represented in the form of audio frequency signals intended
`to be communicated to a human subject. Typical audio
`frequencies are in the range of from about 100 HZ to about
`10,000 HZ. Those audio frequencies that are critical for
`speech detection are typically in the range of from about 500
`HZ to about 2,500 HZ.
`For the purposes of the present invention, the electrical
`audio frequency signal 12 is upshifted in frequency by
`means of single sideband amplitude modulation of an ultra
`sonic frequency carrier signal; that is, an amplitude modu
`lated signal in Which one of the sidebands is entirely or
`substantially suppressed and in Which only a single pre
`dominant sideband remains. In the embodiment of FIG. 1, a
`carrier generator 14 generates an ultrasonic frequency elec
`trical carrier signal Which is preferably in the form of a
`sinusoidal signal at 15. As used herein, the term “ultrasonic
`frequencies” means frequencies Which are above the normal
`human hearing range Which is generally accepted as having
`an upper cut-off frequency of about 20,000 HZ. In a pre
`ferred embodiment of the present invention, an ultrasonic
`carrier Frequency of about 30 kHZ Was found to provide
`good results.
`Asingle sideband amplitude modulator 16 is provided for
`accepting the electrical audio frequency signal 12 and the
`
`Page 5 of 8
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`

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`US 6,169,813 B1
`
`3
`ultrasonic carrier signal 15 and amplitude modulating the
`carrier signal 15 With the audio frequency signal 12 to form
`an ultrasonic single sideband amplitude modulated signal at
`17.
`The single sideband amplitude modulated signal 17 is
`formed With one sideband entirely or substantially sup
`pressed or attenuated such that only a single predominant
`sideband remains. Suppression of one sideband can be
`accomplished in several different Ways such as by ?ltering
`out or attenuating one of the sidebands, by using phase shift
`techniques or by using vestigial sideband modulation. Ves
`tigial sideband modulation, Which is included Within the
`scope of single sideband modulation for purposes cf the
`present invention, is a form of modulation in Which one
`sideband is substantially but not completely suppressed and
`in Which one remaining sideband is predominant. Such
`single sideband suppression techniques are knoWn to those
`skilled in the art and Will be discussed beloW in further
`detail. All such single sideband techniques fall Within the
`scope of the present invention as applied to the frequency
`shifted single sideband amplitude modulated ultrasonic fre
`quency signal 17. Accordingly, as used herein, a “single
`sideband amplitude modulated signal” is one in Which one
`of the sidebands is substantially suppressed such that only a
`single predominant sideband remains.
`The ultrasonic single sideband amplitude modulated sig
`nal 17 is connected to a second transducer 18 Which converts
`the input signal 17 to a vibratory signal at 19. The vibratory
`signal 19 is mechanically connected to an applicator 20
`Which applies the vibratory signal to a portion of the human
`body as represented at 21. The vibratory signal 19 may be of
`any physical form suitable for application to the human body
`to create a physical stimulus and may thus include physical
`ultrasonic Wave pulsations transmitted a short distance
`through the air by the applicator 20 to physically impact the
`target portion of the body to Which the vibratory signal is to
`be applied. For example, the applicator 20 may be in the
`form of a speaker Which creates physical vibrations in the
`air, Which vibrations are transmitted in Wave form through
`the air to impact a selected portion of the body Which has
`been determined to be responsive to physically applied
`vibrations. In such a case, the vibrations are directly physi
`cally applied to the selected portion of the human body by
`means of the interaction With and the resultant vibratory
`impact on the selected human body portion of the ultrasonic
`vibrations transmitted as Waves through the air as a medium.
`The terms “applicator” and “applicator means” as used
`herein include all such apparatus.
`The transducer 18 and the applicator 20 may be integrated
`into a single unit Wherein the vibratory portion of the
`transducer 18 functions also as the applicator 20. Such an
`integrated unit is shoWn in cross sectional form in FIG. 2(a)
`in Which a pieZoelectric element 70 is positioned betWeen
`electrodes 72 and 74, Which are connected to the frequency
`upshifted modulated signal 17. The pieZoelectric element 70
`eXpands and contracts in response to the varying electric
`?eld applied through the electrodes to produce a vibratory
`signal in response to the input signal 17. An output pad 76,
`Which is preferably formed of a ?rm but someWhat resilient
`insulating material such as a plastic material, is attached to
`electrode 74 for applying the vibrations thus produced
`directly to the human body portion 21.
`The circuitry of a single sideband modulation system
`suitable for functioning as the modulator 16 is shoWn in
`block diagram form in FIG. 2. Before describing the cir
`cuitry of FIG. 2, a description of one methodology for the
`modulation of the audio frequency signal 12 onto the carrier
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`signal 15 Will be presented. In this ?rst described
`methodology, substantially complete suppression of one
`sideband is attained. In other methodologies, as further
`described beloW, substantial suppression of one sideband is
`attained although some vestiges of the suppressed sideband
`may still remain.
`Single sideband amplitude modulation in accordance With
`the present invention may be carried out, for eXample, using
`the circuitry shoWn in FIG. 2 in Which one sideband is fully
`suppressed. In this embodiment, the audio frequency signal
`12 may be represented as a function of time as X(t) and the
`carrier signal as 006. To form directly an upper sideband
`modulated signal Xc(t) in Which the carrier 006 is modulated
`by X(t), the folloWing mathematical relationship applies:
`
`(1)
`
`Where:
`t is time
`Xc(t) is the modulated frequency upshifted signal
`X(t) is the audio signal 12
`>A((t) is X(t) shifted by 90°
`we is the carrier or upshift frequency in radians
`It Will be observed from equation (1) that the elements of
`the equation must be computed and the operations per
`formed in accordance With the equation to yield the single
`sideband modulated upshifted signal Xc(t). As set forth in
`equation (1), Xc(t) is an upper sideband modulated signal. A
`loWer sideband signal may instead be formed by using the
`appropriate mathematical relationship of the elements. Thus,
`in accordance With the present invention, the signal Xc(t)
`may be single sideband modulated utiliZing either the upper
`or the loWer sideband. In the embodiment presented herein,
`the signal Xc(t) is modulated With the upper sideband.
`In the embodiment of FIG. 2, the electrical audio signal 12
`is split at 22 and is directed both to a phase shifter 24 and
`a multiplier 26. The phase shifter 24, Which may be an
`element of a Hilbert transform phase shifter, produces a
`minus 90° phase shift in signal 12 to output a signal 28,
`Which is
`The carrier generator 14 generates an ultra
`sonic frequency carrier signal 15 Which is connected to
`cosine function generating element 30, Which forms cos (net
`at 32.
`The cos uuct signal 32 is connected to multiplier 26 Where
`it is multiplied by X(t) signal 12 to form X(t)cos uuct at 34.
`The cos uuct signal 32 is also connected to another phase
`shifter element 36, Which may be another element of a
`Hilbert transform phase shifter along With element 24, to
`produce a minus 90° phase shifted signal at 38, Which is sin
`uuct. Signals 28 and 38 are multiplied by each other by a
`multiplier to form signal 40, Which is )Ar(t)sin uuct.
`Signals 34 and 40 are subtracted from each other at
`subtractor 42 to form a single sideband (upper sideband, in
`the eXample given), amplitude modulated ultrasonic fre
`quency signal 44 Which is X(t)cos uuct—fr(t)sin uuct. The single
`sideband, amplitude modulated ultrasonic frequency signal
`44 is connected to transducer 36 and converted to a vibratory
`signal as in the embodiment of FIG. 1 for application to a
`selected portion of the human body for transmission Within
`the body.
`In another embodiment of the present invention, as shoWn
`in FIG. 3, the electrical audio signal 12 is processed through
`a signal processor 13 before it is modulated by the modulator
`16. The signal. processor 13 functions to improve the quality
`of the audio signal 12, such as by ?ltering out noise
`components and other disturbances and performing other
`signal processing functions. The modulator 16 modulates
`
`Page 6 of 8
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`

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`US 6,169,813 B1
`
`5
`the processed signal 12a onto the ultrasonic frequency
`carrier signal 15 and outputs a signal 17a Which is the
`ultrasonic carrier signal 15 modulated With the processed
`signal 12a. The remainder of the circuit of FIG. 3 is the same
`as and operates in the same manner as the embodiment
`shoWn in FIG. 1.
`The signal processor 13 also functions in selected appli
`cations to expand the bandWidth of the audio frequency
`information signal as it is shifted to a higher frequency range
`in order to provide a Wider difference in the frequency
`bandWidth of the audio information signal relative to the
`shifted frequency for purposes of facilitating detection of
`“just noticeable differences” betWeen the adjacent frequen
`cies in the information signal. It is believed that such
`expansion in frequency bandWidth of the audio frequency
`information signal facilitates better detection of the fre
`quency differences in the information signal at the shifted
`higher frequencies for some users of the hearing aid equip
`ment. The amount of the bandWidth expansion can be
`selected to optimiZe the response in individual cases.
`In the embodiment of FIG. 3, the signal processing and/or
`bandWidth expansion of the audio frequency information
`signal 12 is preferably effected before the frequency shift of
`the information signal to the higher frequency range. Where
`the frequency shift is effected by amplitude modulation of a
`higher frequency carrier signal, the bandWidth of the audio
`frequency information signal is expanded prior to the modu
`lation of the carrier.
`The expansion of the bandWidth of the audio frequency
`signal information signal may be effected by techniques
`knoWn in the art. Examples of such techniques are shoWn in
`US. Pat. No. 4,419,544—Adelman and US. Pat. No. 4,051,
`331—Strong. As disclosed in the referenced Adelman
`patent, harmonic transposition of frequencies from one
`frequency band to another is accomplished by selective
`multiplication cr division of all component frequencies by a
`constant value. Such bandWidth expansion may also be
`accomplished by means of “Fast Fourier Transforms” to
`derive numerically the Fourier transforms of the component
`frequencies of the audio frequency signal for enabling
`frequency translations to be performed in a Well knoWn
`manner such as described in the aforementioned Adelman
`and Strong patents.
`Such Fast Fourier Transform techniques are described, for
`example, in the book “Introduction to Communication Sys
`tems” Second Edition, by Ferrel G. Stremler, published in
`1982 by Addison-Wesley Publishing Company, dealing With
`Fast Fourier Transform (FFT) techniques. As noted on pages
`136—141 of the aforementioned book, the commonly used
`Cooley-Tukey FFT algorithm computes N discrete fre
`quency components from N discrete time samples of a
`signal, Where N is any selected number Which is an integer
`poWer of 2. The speci?cs of the FFT techniques using this
`algorithm are described in detail in the referenced portion of
`the text, the subject matter of Which is incorporated herein
`by reference.
`In another embodiment of the present invention as shoWn
`in FIG. 4, single sideband modulation is accomplished by
`?ltering out one of the sidebands. In this embodiment, the
`ultrasonic carrier frequency signal generator generates car
`rier signal 15 as in the embodiment of FIG. 3 and cosine
`generator 30 generates cos we signal 32. The audio fre
`quency signal 12, represented as a function of time x(t) and.
`the cos we signal 32 are connected to a multiplier 50, Which
`multiplies the tWo signals to form the double sideband
`modulated signal x(t)cos 006 at 52.
`A sideband ?lter 54 ?lters out a selected upper or loWer
`sideband to form a substantially single sideband modulated
`
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`signal 17, Which is the signal 17 in the embodiment of FIG.
`1. In the case Where the upper sideband is the predominant
`sideband, the ?lter 54 is a high pass ?lter Which cuts off in
`the vicinity of the frequency band of the loWer sideband. In
`the case Where the loWer sideband is the predominant
`sideband, the ?lter 54 is a loW pass ?lter Which cuts off the
`frequency band of the upper sideband. Aband pass ?lter may
`also be used as the ?lter 54 to ?lter out a selected one of the
`sidebands.
`Ideally, the ?lter 54 should have a sharp cutoff in the
`vicinity of the carrier frequency to reject all frequency
`components on one side of the carrier frequency. HoWever,
`since it is impossible to achieve an ideal ?lter characteristic,
`some compromise must be made in the realiZation of the
`actual ?lter characteristics and ?lters With some ?nite slope
`approaching the carrier frequency must be used. The audio
`bandWidth can be selected, particularly With respect to the
`loWer frequencies Which are to be utiliZed, such that the loW
`frequency components complement the ?lter design. Vesti
`gial sideband modulation, in Which one of the sidebands is
`substantially attenuated relative to the other sideband by the
`?lter 54, may also be used in the present invention. The
`advantages of the present invention may thus be attained
`Where a substantial portion of one of the sidebands is
`attenuated or suppressed and all of the foregoing thus fall
`Within the scope of the term “single sideband amplitude
`modulated signal” as that term is de?ned above.
`Referring noW to FIG. 5, there is shoWn a con?guration
`utiliZing the improved hearing aid apparatus of the present
`invention in Which hearing aid assemblies 60a and 60b are
`positioned on both sides of the head 62 of a user. The
`assemblies 60a and 60b are supported in place in contact
`With opposite sides of the head of the user by a resilient
`holder 61, Which resiliently urges the assemblies 60a and
`60b against the sides of the head of the user, preferably in
`contact With bone portions of the skull.
`In a preferred embodiment of FIG. 5, both of the assem
`blies 60a and 60b are each a complete assembly of the
`elements 10, 14, 16, 18 and 20 of FIG. 1 or of elements 10,
`13, 14, 16, 18 and 20 of FIG. 2. The audio frequency sounds
`that are detected and frequency upshifted by the assemblies
`60a and 60b are therefore those Which impinge at opposite
`sides of the head 62 of the user. Because the sounds thus
`detected and frequency upshifted for hearing response are
`positionally displaced from each other on the opposite sides
`of the head of the user, the con?guration of FIG. 5 is useful
`for improved hearing perception and for special purposes
`such as, for example, echo detection.
`In another embodiment of the con?guration of FIG. 5,
`only the assembly 60a contains the full complement of the
`elements of FIG. 1 or FIG. 2. The other assembly 60b
`contains only the elements 18 and 20 and the frequency
`upshifted signal 17 is carried by an electrical conductor in
`the holder 61 from the assembly 60a to the assembly 60b. In
`this arrangement, the audio signal is detected only on the
`side of the head on Which the assembly 60a is positioned and
`the same frequency upshifted signal 17 is then applied to the
`transducer 18 and applicator 20 positioned in each of the
`assemblies 60a and 60b. In this embodiment, therefore, the
`same frequency upshifted signal 17 is applied through
`combinations of transducers 18 and applicators 20 posi
`tioned on opposite sides of the head.
`The embodiment of FIG. 5 may take other forms in Which
`the frequency upshifted signal 17 is applied to multiple
`transducers 18 and applicators 20 positioned at various other
`points on the body of the user.
`It is to be understood that the embodiments set forth
`herein are described in detail for purposes of providing a full
`
`Page 7 of 8
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`US 6,169,813 B1
`
`7
`and complete disclosure of the best mode of the present
`invention and of practicing the same, and that such detailed
`disclosure is therefore not to be interpreted as in any Way
`limiting the scope of the present invention as de?ned in the
`appended claims. Various rnodi?cations and substitutions
`falling Within the scope of the teachings set forth herein and
`Within the scope of the appended claims Will therefore occur
`to those skilled in the art.
`What is claimed is:
`1. A hearing aid apparatus for receiving and transmitting
`to the human sensory system an audio frequency signal for
`enabling hurnan sensing of information contained in said
`audio frequency signal cornprising:
`?rst transducer means for converting an audio frequency
`sound signal into an audio frequency electrical signal;
`generating means for generating an ultrasonic frequency
`electrical carrier signal;
`single sideband arnplitude rnodulating means for ampli
`tude rnodulating said audio frequency electrical signal
`onto said ultrasonic frequency electrical carrier signal
`to form a single sideband arnplitude rnodulated elec
`trical signal;
`second transducer means for converting said single
`sideband, arnplitude rnodulated electrical signal into a
`vibratory signal; and
`applicator means for applying said vibratory signal to the
`human sensory system through physical interaction
`With the human body.
`2. Ahearing aid apparatus as set forth in claim 1 in Which
`said single sideband arnplitude rnodulating means comprises
`a phase shifter for forming a quadrature phase shifted signal
`from said audio frequency signal and providing said quadra
`ture phase shifted signal and said audio frequency signal to
`said arnplitude rnodulating means to form said single side
`band arnplitude rnodulated electrical signal.
`3. A hearing aid apparatus as set forth in claim 1 Wherein
`said single sideband arnplitude rnodulating means includes
`means for substantially suppressing one of the sidebands
`relative to the other.
`4. A hearing aid apparatus as set forth in claim 1 Wherein
`said applicator means includes means for applying said
`vibratory signals to a portion of the head of a user.
`5. A hearing aid apparatus as set forth in claim 4 Wherein
`said second transducer means and said applicator means are
`con?gured for generating and applying said vibratory signal
`to a portion of one side of the head; and including third
`
`10
`
`15
`
`25
`
`35
`
`45
`
`8
`transducer means for converting said single sideband, ampli
`tude rnodulated electrical signal into a second vibratory
`signal and second applicator means for generating applying
`said second vibratory signal to a portion of the other side of
`the head.
`6. A hearing aid apparatus as set forth in claim 4 Wherein
`said applicator means includes means for applying said
`vibratory signal to a portion of the head of a user for bone
`conduction Within the head.
`7. A hearing aid apparatus as set forth in claim 1 further
`comprising a signal processor for rnodi?cation of said audio
`frequency electrical signal to improve the clarity of per
`ceived hearing of the user.
`8. A hearing aid apparatus as set forth in claim 7 Wherein
`said signal processor includes means for eXpanding the
`bandWidth of said audio frequency electrical signal at said
`ultrasonic frequency carrier signal frequency.
`9. A hearing aid apparatus as set forth in claim 1 Wherein
`said second transducer means comprises a pieZoelectric
`transducer for converting said single sideband, arnplitude
`rnodulated electrical signal into a vibratory signal.
`10. A method of generating a hearing response in the
`human body comprising:
`converting an audio frequency sound signal, as to Which
`a hearing response is to be generated, into an audio
`frequency electrical signal;
`generating an ultrasonic frequency electrical carrier sig
`nal;
`arnplitude rnodulating said audio frequency electrical
`signal onto said ultrasonic frequency electrical carrier
`signal to thereby form a single sideband arnplitude
`rnodulated electrical signal;
`converting said single sideband, arnplitude rnodulated
`electrical signal into a vibratory signal; and
`applying said vibratory signal to the human sensory
`system through physical contact With the human body
`to thereby generate a hearing response to said audio
`frequency sound signal.
`11. The method of claim 10 including forming a quadra
`ture phase shifted signal from said audio frequency signal
`and utiliZing said quadrature phase shifted signal and said
`audio frequency signal in amplitude rnodulating said ultra
`sonic frequency electrical carrier signal to form said single
`sideband arnplitude rnodulated electrical signal.
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