U.S. patent application number 10/135395 was filed with the patent office on 2002-11-21 for tinnitis masking.
This patent application is currently assigned to SOUND TECHNIQUES SYSTEMS LLC. Invention is credited to Lenhardt, Martin L..
Application Number | 20020173697 10/135395 |
Document ID | / |
Family ID | 22299353 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020173697 |
Kind Code |
A1 |
Lenhardt, Martin L. |
November 21, 2002 |
Tinnitis masking
Abstract
A system and method for tinnitus masking. Ultrasound noise is
provided to a head of a patient as a vibration by way of a
transducer, to thereby stimulate the auditory cortex. Once
stimulated, the auditory cortex will suppress tinnitus. The
ultrasound noise may be provided as an ultrasound frequency tone or
as a range of frequencies that have been multiplied with an audio
frequency. Pulsed ultrasound is utilized for ultrasound noise in
the MHz range.
Inventors: |
Lenhardt, Martin L.; (Hayes,
VA) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
SOUND TECHNIQUES SYSTEMS
LLC
|
Family ID: |
22299353 |
Appl. No.: |
10/135395 |
Filed: |
May 1, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10135395 |
May 1, 2002 |
|
|
|
09417772 |
Oct 14, 1999 |
|
|
|
6394969 |
|
|
|
|
60104233 |
Oct 14, 1998 |
|
|
|
Current U.S.
Class: |
600/25 ;
601/2 |
Current CPC
Class: |
A61B 8/0808 20130101;
H04R 25/75 20130101; A61B 5/12 20130101; A61F 11/00 20130101; A61N
7/00 20130101 |
Class at
Publication: |
600/25 ;
601/2 |
International
Class: |
H04R 025/00 |
Claims
What is claimed is:
1. A tinnitus masker, comprising: an ultrasound source configured
to output at least one ultrasound frequency; and a vibration unit
connected to the ultrasound source and configured to convert the at
least one ultrasound frequency to a vibration, wherein the
vibration unit is coupled to a person who experiences tinnitus in
order to provide a vibration within a brain of the person to
thereby mask the tinnitus.
2. The tinnitus masker according to claim 1, further comprising an
amplifier and power supply unit connected between the ultrasound
unit and the vibration unit and configured to control an amplitude
level of the at least one ultrasound frequency to be no more than
20 dB greater than a threshold level of sound for the person.
3. The tinnitus masker according to claim 1, wherein the at least
one ultrasound frequency is a frequency of between 20 kHz and 200
kHz.
4. The tinnitus masker according to claim 1, wherein the at least
one ultrasound frequency is a frequency of between 10 kHz and 200
kHz.
5. The tinnitus masker according to claim 1, wherein the at least
one ultrasound frequency is a frequency of between 200 kHz and 5
MHz.
6. The tinnitus masker according to claim 1, wherein the at least
one ultrasound frequency is a frequency of between 20 kHz and 5
MHz.
7. The tinnitus masker according to claim 1, further comprising a
pulser connected between the ultrasound unit and the vibration unit
and configured to pulse the at least one ultrasound frequency at a
rate less than a 10 Hz rate.
8. The tinnitus masker according to claim 3, wherein the at least
one ultrasound frequency is swept over a range of frequencies
centered at the at least one ultrasound frequency.
9. The tinnitus masker according to claim 4, wherein the at least
one ultrasound frequency is swept over a range of frequencies
centered at the at least one ultrasound frequency.
10. The tinnitus masker according to claim 5, wherein the at least
one ultrasound frequency is swept over a range of frequencies
centered at the at least one ultrasound frequency.
11. A method of masking tinnitus, comprising the step of: a)
providing ultrasound noise to a head of a patient.
12. The method according to claim 11, wherein the ultrasound noise
is noise within a range of from 20 kHz to 200 kHz.
13. The method according to claim 11, wherein the ultrasound is
noise within a range of from 10 kHz to 200 kHz.
14. The method according to claim 11, wherein the ultrasound is
noise within a range of from 200 kHz to 5 MHz.
15. The method according to claim 14, further comprising the step
of: b) pulsing the ultrasound noise before applying the ultrasound
noise to the head of the patient.
16. A method of examining a patient in order to provide an
ultrasound treatment for that patient, comprising the steps of:
providing a plurality of ultrasound frequency tones, in sequence,
to the patient, to determine an optimum ultrasound frequency for
the patient; and providing a plurality of audible frequencies
modulated by the determined optimum ultrasound frequency, so as to
determine a particular audible frequency that is optimum for the
patient with respect to ultrasound tinnitus masking.
Description
[0001] This application claims priority of U.S. Provisional
Application No. 60/104,233 filed in the U.S. Patent and Trademark
Office on Oct. 14, 1998, the entirety of which is incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a system and method for
masking tinnitus. In particular, the present invention relates to a
system and method for masking tinnitus using high frequency signals
that affect the cortical auditory neurons in the brain.
[0004] 2. Description of the Related Art
[0005] Tinnitus is defined as any ringing in the ears for which
there is no external source. For example, a ringing, buzzing,
whistling, or roaring sound may be heard as a result of tinnitus.
Tinnitus can be continuous or intermittent, and in either case can
be very irritating to one who has such an affliction.
[0006] Prior to the present invention, there has been no
consistently effective way to counter, or mask, tinnitus. Most of
the attempts to date have focused on masking the perceived sound.
For example, U.S. Pat. No. 4,222,393, issued to Robert Hocks et
al., describes a tinnitus masker that provides sounds in the range
of from 1000 Hz to 5000 Hz, with a peak around 3000 or 4000 Hz. The
patient is provided with sounds of varying pitch, one after
another, so that the patient can identify the particular external
sound having the same pitch as the tinnitus that the patient is
experiencing. Once this is done, a power operated sound is applied
to the ear of the patient, with that sound including a range of
frequencies extending in a range above and below the perceived
pitch.
[0007] U.S. Pat. No. 4,226,248, issued to Samir Manoli, describes a
phonocephalographic device, which is used to passively,
non-invasively monitor sounds from the surface and cavities of a
patient's head and correlate these sounds with a person's
elecytrocardiagraph (ECG). A pair of insertable ear microphones of
ample sensitivity are inserted into the patient's ears, where they
detect sounds from the surface and cavities of the head. These
signals are processed, with the processing including the filtering
of these signals through a frequency analyzer, which is made up of
four Butterworth filters with a variable center frequency of
between 150 Hz and 1000 Hz. In addition, the output signals may be
passed to a oscillator for display on an oscilloscope, and or may
be displayed on a chart recorder. As such, this apparatus may be
used to diagnose certain medical problems of the patient, including
tinnitus.
[0008] U.S. Pat. No. 4,759,070, issued to Barry Voroba et al.,
describes a patient controlled master hearing aid. The device
includes a hearing test module and an operator's and patient's
console. Based on this testing apparatus, the patient can select
electronic components to be employed in his or her hearing aid,
which can be configured to address tinnitus. Testing and selection
of a tinnitus masker are performed using a pseudo-random generator,
which is connected to circuits through an analog switch. U.S. Pat.
No. 4,984,579, issued to Paul Burgert et al., describes a portable
apparatus for treating afflictions of the ear. The apparatus
temporarily changes the pressure in the ear canal to alleviate
Meniere's symptoms, such as hearing loss, vertigo, tinnitus,
nausea, and aural fullness, in which the patient can facilitate
immediate self-treatment.
[0009] U.S. Pat. No. 5,024,612, issued to van den Honert et al.,
describes an external ear canal pressure regulating device and
tinnitus suppression device. This device uses an in-the-canal
external ear pressure-regulating device to alter the pressure of
the fluid within the external ear canal. The device includes an
earplug with a bulbous portion, which contacts the wall of the
external ear canal and creates a seal that seals the external ear
canal interior from the ambient environment. The earplug is
inserted into the ear canal, and the bulbous end is compressed.
Fluid is passed outwardly into the ambient environment through a
valve, creating negative pressure in the exterior ear canal, which
pulls the eardrum out. This decreases the pressure in the inner ear
space. Once the bulbous end is released, it re-expands. This
process can be repeated until the desired pressure differential, or
tinnitus relief, is achieved.
[0010] U.S. Pat. No. 5,167,236, issued to Franz Junker, describes a
tinnitus masker having an electric circuit arranged in a housing
and an earpiece which produces a sound spectrum that masks the
tinnitus. The sound spectrum contains a line spectrum with a
fundamental tone, with an adjustment range of the fundamental tone
of from 0.125 kHz to 20 kHz.
[0011] U.S. Pat. No. 5,325,827, issued to Saren Westermann,
describes a tinnitus masker which uses one or more signal
generators, a controllable amplifier, one or two electroacoustic
transducers for converting the electrical signals into acoustic
signals, and a voltage source. The signal generators generate a
continuously repeated, sinusoidal pure tone signal which slowly
moves through the audio frequency range and whose cycle duration
can be adjusted between 0.1 and 1000 seconds.
[0012] U.S. Pat. No. 5,403,262, issued to Timothy Gooch, describes
a minimum energy tinnitus masker, which produces a masking signal
with a selected center frequency, selected bandwidth, and selected
volume. The bandwidth selector allows for four selections, 1/8,
1/2, 1 octave bandwidth, as well as broad bandwidth; and the center
frequency selector is selectable in a range of between 500 and
16,000 Hz.
[0013] U.S. Pat. No. 5,628,330, issued to George Upham, describes
an apparatus for treating people who are afflicted with tinnitus.
This apparatus includes an inner metal shell that is fitted onto a
patient's head. The inner metal shell is nestled with a larger
outer shell of similar characteristics. The patient experiences
relief from tinnitus by holding an open end of the apparatus
against the afflicted ear. The inventor of the '330 patent believes
that his apparatus may focus or somehow direct the "natural healing
process" of the human body to the injured part of the inner ear
and/or direct external healing to the injured part of the inner
ear. See column 4, lines 1-6.
[0014] U.S. Pat. No. 5,697,975, issued to Matthew Howard III, et
al., describes a human cerebral cortex neural prosthetic for
tinnitus. Howard's device can be positioned in the brain so that
electrical discharges can be accurately transmitted to
geometrically dispersed locations in either a cortex or the
thalamus, to allow a physician to physiologically test location and
function of the neural prosthetic electrodes to reduce/eliminate
the patient's tinnitus. In this regard, Howard's invention treats
tinnitus in the brain, and not in the inner ear. In particular,
Howard describes that the normal transduction of sound waves into
electrical signals occurs in the cochlea, which is a part of the
inner ear located within temporal bone. The cochlea is
tonotopically organized, which means that different parts of the
cochlea respond optimally to different tones. One end of the
cochlea (base) responds best to high frequency tones, while the
other end (apex) responds best to low frequency tones. The cochlea
converts the tones to electrical signals, which are then received
by the cochlear nucleus in the brain. This converted information is
passed from the cochlea into the brain stem by way of electrical
signals carried along the acoustic nerve, and in particular, the
cranial nerve VIII. As the acoustic nerve leaves the temporal bone
and enters the skull cavity, it penetrates the brain stem and
relays coded signals to the cochlear nucleus, which is also
tonotopically organized. Through many fiber-tract interconnections
and relays, sound signals are analyzed at sites throughout the
brain stem and the thalamus, with the final signal analysis site
being the auditory cortex situated in the temporal lobe of the
brain.
[0015] U.S. Pat. No. 5,663,727, issued to Peter Vokac, describes a
frequency response analyzer and shaping apparatus, and digital
hearing enhancement apparatus. The device provides many of the
characteristics of a complete fast fourier transform suitable for
audio signals and other signals. Vokac's device customizes the
frequency response for a particular patient, by providing an FFT'ed
signal in an audible frequency range.
[0016] U.S. Pat. No. 5,692,056, issued to William Gardner,
describes a method and apparatus for intracranial noise
suppression. Vibrations from an instrument, as well as vibrations
in the bone structure of the patient, are sensed and processed to
generate canceling noise, which is then fed into the inner ear
through vibrations on the head. Gardner's device also includes an
equalizer and an automatic adaptive coupler.
[0017] Also, there is on the market an electrical tinnitus
suppressor called "Theraband.RTM.". This is a battery powered
headset that delivers amplitude modulated radio frequency waves to
the subject. The carrier is about 60 (Hz (possibly variable), with
audio frequencies in the 200 Hz to 20,000 Hz range. The means of
delivery is to the ear of the subject, where the sounds are
received like any other sound. Theraband.RTM. uses electrical
energy capacitively coupled to the head via electrodes on
mastoid.
[0018] All of the above-mentioned tinnitus maskers do not appear to
fully mask tinnitus, since they do not appreciate the true reason
why tinnitus occurs. In particular, these conventional tinnitus
maskers/suppressors operate under the assumption that the tinnitus
problem is in the inner ear, and they attempt to provide a solution
that is based on this assumption.
SUMMARY OF THE INVENTION
[0019] The invention is directed to a tinnitus masker, which
includes an ultrasound source configured to output at least one
ultrasound frequency. The masker also includes a vibration unit
connected to the ultrasound source and configured to convert the
ultrasound frequency to a vibration. The vibration unit is coupled
to a person who experiences tinnitus, thereby providing a
stimulation of the brain of that person, which in turn causes
tinnitus masking.
[0020] The invention is also directed to a method of masking
tinnitus, which includes a step of providing ultrasound noise to a
head of a patient.
[0021] The invention is further directed to a method of examining a
patient in order to provide an ultrasound treatment for that
patient. The method includes a step of providing a plurality of
ultrasound frequency tones, in sequence, to the patient, to
determine an optimum ultrasound frequency for the patient. The
method also includes a step of providing a plurality of audible
frequencies modulated by the determined optimum ultrasound
frequency, so as to determine a particular audible frequency that
is optimum for the patient with respect to ultrasound tinnitus
masking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The above-mentioned object and advantages of the invention
will become more fully apparent from the following detailed
description when read in conjunction with the accompanying
drawings, with like reference numerals indicating corresponding
parts throughout, and wherein:
[0023] FIG. 1 is a block diagram of a tinnitus masker according to
first and second embodiments of the invention;
[0024] FIG. 2 is a block diagram of a tinnitus masker according to
a third embodiment of the invention; and
[0025] FIG. 3 is a diagram showing a brain-sphere model used to
determine resonant frequencies of a brain.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] The embodiments of the invention are directed to a method
and a system for masking tinnitus, and may even suppress tinnitus.
The incidence of tinnitus increases with age, affecting almost half
of the population over seventy. Tinnitus is believed to exist in
around 15% of the population. See 1989 National Strategic Research
Plan, published by the National Institutes of Health, and referred
to in U.S. Pat. No. 5,697,975, discussed in the Background section.
Tinnitus is very often associated with hearing loss and noise
exposure. Tinnitus can be described as a phantom sound (e.g.,
whistling, buzzing) that arises without any external stimulation.
Often the source of tinnitus is assigned to the ear because it
"sounds" like a sound, that it has the pitch, loudness and timbre
of a sound. Tinnitus can be matched in quality to an external
sound, and it is often associated with one ear or the other, or
both ears. Tinnitus can often be masked by an external sound, as
discussed in the Background section. There have been reports that,
with the withdrawal of masking, tinnitus does not immediately
reappear. This is termed tinnitus suppression. Suppression is
typically short lived, and masking may again be required. The
suppression phenomena is valuable in that masking may only be
required for part of the day, such as for a short period of time in
the morning, with the rest of the day being "tinnitus free" due to
tinnitus suppression.
[0027] The fact that tinnitus is maskable suggests to most
researchers that the source of tinnitus is in the ear to which it
is localized. If this were true, then tinnitus masking would be
nearly 100% effective using the method and apparatuses discussed in
the Background section, which is not the case. In fact, the
matching of tinnitus with an external sound can be very difficult
and is often unreliable. This had lead some to refine the masking
energy in both spectrum and intensity, so-called minimum level of
masking.
[0028] Alternatively, there are some researchers that pose a
central origin to tinnitus, with that central origin being beyond
the ear and in the brain. For example, an article by Lockwood et
al., published in 1998, found widespread activation of the primary
cortex contralateral to the ear as being the source of tinnitus. In
other words, the source of tinnitus is actually cortical and not in
the ear. This is a reasonable view since it has been demonstrated
that auditory cortical neuron reprogramming in the ear is not
capable of providing frequency-specific stimulation. The
reprogramming process may well produce tinnitus as a by-product.
Perceptually, the source of cortical stimulation is directed to the
peripheral sensory end organ. The reason for failure of attempts to
mask or pharmaceutically treat tinnitus in the ear may well be that
the ear is not the site of tinnitus!
[0029] This view of having a central origin for the source of
tinnitus is supported by the lack of success with conventional
tinnitus maskers, and also with the observations that after
surgically severing the auditory nerve, tinnitus persists, and
further with position emission tomography (PET) scans. The neural
imaging data show that tinnitus activates the primary auditory
cortex contralateral to the ear in which the tinnitus is localized,
with that area activated being broader than that activated by
sounds of similar frequency. This is one important reason why
conventional tinnitus maskers fail, since they do not completely
mask the tinnitus at the central origin or location. To broaden the
frequency spread at the cortex, a masking signal that is broader
and louder at the ear must be provided. However, when such a signal
is given to patients who suffer from tinnitus, they find that the
masker is more intolerable than the tinnitus. In other words, the
cure is worse than the disease.
[0030] To determine a better cure for tinnitus, one has to
understand the workings of the inner ear and the brain. External
sounds activate both primary cortices, and each cortex is connected
to a respective ear via a descending auditory nervous system.
Maskers have an additional limitation in that if fitted on the left
ear due to tinnitus localized left, both auditory cortices are
stimulated, even though only the right cortex is activated by the
tinnitus. The masker will in fact interfere with normal auditory
function in the brain, and this will contribute to patient
intolerance and discomfort. The brain will actively try to reduce
the amount of masking arising up the auditory pathway by activating
the descending auditory neural track. The result is that the brain
will try to turn down the masker, limiting its effectiveness.
[0031] As a result, what is needed is a stimulus that is
sufficiently salient to mask the tinnitus, but is not treated as an
unwanted signal that will be inhibited by the brain. A masker that
provides such a stimulus will be effective in terms of auditory
cortical activation, and will not interfere with everyday important
sounds, such as speech. Such a masker will be effective with people
having hearing loss.
[0032] While there may be disagreement about the site of tinnitus
(ear versus brain), most researchers agree that tinnitus and
hearing loss are linked. Although documentation is incomplete, some
deaf individuals also complain of bothersome tinnitus. Conventional
tinnitus maskers are not very effective with those persons who have
profound hearing loss. Also, it is desirable to have a masker that
is audible only to the patient and does not radiate into the
environment. Maskers that are implanted into the middle ear fit
this criterion, but other types of maskers do not.
[0033] The masking stimulus that will meet all of the above
criteria, and that is used in the tinnitus masker and method
according to one embodiment of the invention, is ultrasonic noise.
This noise can be made up of any part of the spectrum from 20,000
Hz up to 200,000 Hz. In a second embodiment, the noise band may
extend from 10,000 Hz to 200,000 Hz, but it must be noted that the
frequencies from 10,000 Hz to 20,000 Hz typically are not as
effective in suppressing tinnitus as the higher frequencies. In a
third embodiment, frequencies in an imaging frequency band of from
200,000 Hz to 5 MHz may be used with or without the other ranges in
the first two embodiments.
[0034] There have been two reports of ultrasonic tinnitus
suppression in the literature: Carrick et al., 1986 British Journal
of Audiology, vol. 20, pages 153-155; and Rendell et al., 1987
British Journal of Audiology, vol. 21, pages 289-293. The Carrick
article reported positive findings using a 500 kHz pulsed
ultrasonic suppressor that produced 57 kPa of energy at 1 cm with 4
mW cm.sup.2 of power. The Rendell article failed to replicate those
findings using the same equipment and drawing subjects from the
same clinic population. This technique appears to have been
abandoned.
[0035] Pulsed ultrasound in the low to mid kHz has been shown to
introduce lower frequency transients into the signal. It is now
believed that the low frequency ultrasound that was effective in
tinnitus suppression in the above-mentioned studies. Since this
feature was not presented optimally or perhaps consistently, varied
positive results could be expected, as is the case with the
differences in results in the two studies.
[0036] In the case the MHz tonal or noise frequencies used
according to the third embodiment of the invention, the stimulus is
provided in a pulsed manner. The rate of pulsing is not critical,
but a slow rate of pulsing, such as a rate from 1-10 Hz, is
preferred. Because the tinnitus masker according to the embodiments
of the invention is high pitched and broad in spectrum, the
tinnitus-affected area of the cerebral cortex will virtually all be
masked. Since the delivery intensity will be low, minimal energy
(re: threshold) will be expended. Since ultrasound is difficult to
detect by air conduction, the masker will be personal and inaudible
to others who may be nearby the person undergoing tinnitus masking
treatment. Since those with severe hearing loss can detect
ultrasound, such as by using a supersonic bone conduction hearing
aid as described in U.S. Pat. No. 4,982,434, which is incorporated
in its entirety herein by reference, it will address their needs
for a masker. Preliminary results suggest temporary tinnitus
suppression by using an apparatus or method according to the
embodiments of the invention.
[0037] The noise energy that is provided to suppress tinnitus of
from 10 kHz upward can be a tone or filtered noise. It can be
continuous or pulsed. The noise energy is preferably delivered near
or at no more than 20 dB or so above threshold (e.g., between
threshold and 20 dB above threshold). Delivery is preferably by a
vibrator placed on the skin of the head or neck. A MHz pulser, to
be used to deliver MHz noise signals according to the third
embodiment, will preferably be delivered to the skin over the
foreman magnum (back of skull by the neck). A transducer will
preferably be similar to that used in transcranial Doppler
insonation.
[0038] Ultrasound affects not only a wide area in the ear (sending
afferent information to the auditory cortex), but it also affects
the brain itself. Ultrasound actually pulses the brain since the
brain's fundamental resonant frequency is in the low ultrasonic
range to the high audio range (determined by the diameter of the
brain and sound velocity in water). FIG. 3 shows a brain-sphere
model used to compute the brain's fundamental resonant frequency
for two differently-sized brains. The computation of the brain's
fundamental resonant frequency is based on the model of the brain
as a sphere with the skull as a boundary. As a result, a number of
resonant frequencies will be generated when the brain is
pulsed.
[0039] Pulsed ultrasound of noise according to the third embodiment
will also send the brain into oscillation at its resonant
frequency, and thus is also a viable means of stimulation. Delgado
and Monteagudo (1995) demonstrated that low frequency
amplitude-modulated (am) ultrasound can effectively stimulate
cortical neutrons, which was used to stimulate brain tissues for
brain modification. The present invention also stimulates cortical
neurons, but for the purpose of tinnitus masking, which was not
proposed by Delgado and Monteagudo.
[0040] Therefore, the embodiments of the present invention provide
for the use of ultrasound to mask tinnitus by stimulating any
remaining high frequency area in the ear and by suppressing
tinnitus by acting on cortical auditory neurons in the brain.
[0041] FIG. 1 shows a block diagram of an apparatus for tinnitus
masking according to either the first or second embodiments of the
invention. In FIG. 1, a sound source unit 110 produces filtered
noise (over a range of frequencies) or a frequency tone. In the
first embodiment, the ultrasonic energy is presented as an
amplitude modulated carrier that can be set at any discrete
frequency from 20 kHz to 200 kHz. The range can be set to any
discrete frequency from 10 kHz to 200 kHz in the second embodiment,
and anywhere from 200 kHz to 5 MHz in the third embodiment. The
carrier also may be swept over the entire range or part thereof.
The carrier is multiplied by an audio tone in the range of from 1
kHz to 20 kHz. This corresponds to a carrier modulated by audio.
The audio tone can also be presented over a small range or swept
through the entire range of audio frequencies. Sweep time is
variable, and preferably is set to a range of from 2 to 3 minutes.
The flexibility in the carriers and audio frequencies allows a
fitter to set frequency parameters such that the end product is
stimulation over the ultrasonic range of from 20 kHz to at least
200 kHz. Speech also may be employed as part of the audio
frequencies.
[0042] The preferred method of signal transmission is by way of
double sideband modulation (suppressed carrier). Full amplitude
modulation (full am carrier plus both sidebands) or single sideband
modulation (either upper or lower sideband with the carrier and the
other sideband suppressed) can alternatively be utilized.
Modulation depth preferably does not exceed 90%, and the energy
does not exceed 15 kPa (in water at 3.5 cm). Total power is
preferably limited to 30 mW cm.sup.2. Commercially available
piezoelectric transducers are used to deliver the ultrasound in
vibratory form to the patient's head. The precise level of energy
(not to exceed 15 kPa) is to be determined for each patient during
testing of each patient. The ultrasound may be audible during
therapy.
[0043] Referring back to FIG. 1, the sound source unit 110 includes
a filter for producing filtered noise, a timer, or clock. These
elements operate as a pulse filter for ultrasonic noise, with the
timer or clock providing the pulse timing. The output of the sound
source unit 110 is provided to an amplifier and power supply unit
120, which amplifies the signal to the proper level to provide a
signal to the patient at the low, minimal energy, as explained
above. A transducer unit 130 converts the output of the power
supply unit 120 to a vibration, which is felt by the patient. The
transducer unit 130, preferably a piezoelectric device, is placed
somewhere on the patient's head 140, preferably just behind the
ear. Those vibrations are provided to the brain (not shown) within
the skull of the patient's head 140, thereby stimulating the
cortices and masking tinnitus.
[0044] FIG. 2 shows the differences between the delivery of
ultrasound noise according to the first and second embodiments as
compared to the third embodiment. In the third embodiment, a tone
generator 210 provides a tone in the MHz range. The output of the
tone generator 210 is provided to a pulser 220, which provides
pulses of MHz noise at a predetermined rate, say, between 1 and 10
Hz rate. A transducer (part of the ultrasonic noise unit 230) is
preferably situated on the patient's skin on the back of the skull
by the neck. FIG. 2 also shows the delivery of non-pulsed
ultrasonic noise in the range of from 20 kHz to 200 kHz via an
ultrasonic noise unit 230. In FIG. 2, ultrasonic noise unit 230
includes the sound source unit, amplifier and power supply unit,
and transducer unit shown in FIG. 1.
[0045] Thus, according to the embodiments of the invention, an
ultrasonic transducer delivers energy occipitally to the patient,
to thereby mask and/or suppress tinnitus.
[0046] The ultrasound technique discussed herein is not without
some disadvantages. The ultrasound technique does not produce low
frequency stimulation of the inner ear, as with the conventional
electrical maskers. Some tinnitus is low pitched, and thus may not
be masked by the ultrasound technique described herein, but most
tinnitus is not in this range. The electrical signal provided by
the conventional tinnitus maskers is presumably demodulated at the
skin or cochlea, leaving the audio frequencies "in" the inner ear.
However, the ultrasound technique according to the embodiments of
the invention does not appear to demodulate in the cochlea. Rather,
the energy focuses at the base of the cochlea, in the region that
codes audio frequencies from 5,000 Hz upwards.
[0047] However, the embodiments have several advantages over
conventional maskers, some of which have already been described.
Low frequency neural synchronization can be accomplished with
ultrasound when it is amplitude modulated by very low audio
frequencies, for example, 1 Hz to 50 Hz. The precept is of high
pitch sound having a low frequency periodicity. The periodicity can
be increased or decreased by changes in the audio frequency tone.
Thus, the ultrasound tinnitus suppression apparatus and method
according to the embodiments of the invention provides only high
frequency stimulation presumably in the area of damage (as
indicated by the tinnitus pitch). Furthermore, auditory nerve low
frequency synchronous firing can also be incorporated in the
ultrasound treatment regime according to the embodiments of the
invention.
[0048] According to the invention, the site of action in the inner
ear appears to be the hair cells for MHz amplitude modulation, in
which the audio tone is reintroduced by demodulation. In the
ultrasound method and apparatus according to the invention,
demodulation does not appear to take place in the cochlea, but
instead the site of action appears to take place at the cilia of
the hair cells. The cilia have ultrasonic resonance, and a movement
of endolymph by a compressive intracochlear ultrasonic wave may
have rejuvenative effects on the cell directly. Stimulation of
nearby cells (with respect to those injured) will also stimulate
adjunct areas in the central nervous system, which could activate
inhibitory influences in the ear.
[0049] While preferred embodiments have been described herein,
modification of the described embodiments may become apparent to
those of ordinary skill in the art, following the teachings of the
invention, without departing from the scope of the invention as set
forth in the appended claims.
* * * * *