Tinnitus masker for direct drive hearing devices

Tinnitus maskers for direct drive hearing devices are provided. A circuit generates signals corresponding to sounds to mask tinnitus a user perceives. A direct drive hearing device which is coupled to a structure in the user vibrates in response to the signals. The vibrating direct drive hearing device stimulates hearing by vibrating the structure to which it is coupled. A user may select the frequency, intensity and phase of a tone generated. Additionally, a second tone or a background sound may be selected.

BACKGROUND OF THE INVENTION 
The present invention is related to hearing systems and, more particularly, 
to tinnitus masker systems for use with direct drive hearing devices. 
Tinnitus is the perception of sound when there is none present. It is most 
often described as "ringing in the ears" but varies from person to person. 
Some people hear hissing, buzzing, whistling, roaring, high-pitched 
screeches, or a sound like steam escaping from a radiator. Still others 
hear one tone or several tones. Twelve million Americans suffer from a 
severe case of tinnitus and it has been estimated that 20% of the 
population experiences tinnitus at some time in their lives. 
Initially, a person suffering from tinnitus may be worried or frightened 
because she is unsure what is wrong or how serious is the condition. 
Although tinnitus itself is not life threatening, some tinnitus sufferers 
describe the constant noise as irritating while others describe it as 
maddening. The actual medical cause of tinnitus is not clear but it is 
believed that some factors such as exposure to loud noise may produce or 
worsen tinnitus. 
Tinnitus maskers alleviate tinnitus by masking out the perceived sound of 
tinnitus. Conventional tinnitus maskers produce sound of their own to help 
mask the tinnitus sound. Perhaps the simplest tinnitus masker is a 
cassette or compact disk player that plays soothing background sounds like 
rain or surf. It is believed some sufferers find relief because they are 
able to focus on these soothing sounds and "tune out" the tinnitus sounds. 
Other conventional tinnitus maskers generate sounds at selected 
frequencies to cancel out the tinnitus sounds. Thus, "tinnitus masking" 
will be used herein to generally describe masking out tinnitus sounds by 
utilizing background sounds, sounds that cancel the tinnitus sounds, or a 
combination of the two. 
An example of conventional tinnitus masker is the Marsona.RTM. tinnitus 
masker, model #1550, available from Marpac Corporation, Wilmington, N.C. 
The Marsona .RTM. tinnitus masker resembles a clock radio and produces 
sounds through an integrated speaker. Controls on the unit allow a user to 
set the frequency and intensity of the sounds produced. 
Other conventional tinnitus maskers resemble hearing aids and are placed 
within the external ear canal. These tinnitus maskers also produce sounds 
in order to mask the tinnitus sound. 
With so many tinnitus sufferers, there is a great need for other methods 
and systems for masking tinnitus sounds. It is believed that since the 
direct drive hearing devices rely on direct vibrational conduction, they 
may mask tinnitus better than conventional acoustic hearing aids. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus for tinnitus masker systems 
utilizing direct drive hearing devices. A circuit generates signals 
corresponding to sounds to mask tinnitus a user perceives. A direct drive 
hearing device which is coupled to a structure (e.g., an ossicle) within 
the user or patient's body vibrates in response to the signals. The 
vibrating direct drive hearing device stimulates hearing by vibrating the 
structure to which it is coupled. 
In one embodiment, the present invention provides an apparatus for masking 
tinnitus, comprising: a battery; and a circuit, coupled to the battery, 
that generates signals for a direct drive hearing device in order to mask 
tinnitus. Preferably, the direct drive hearing device is a floating mass 
transducer direct drive hearing device. 
In another embodiment, the present invention provides a method of masking 
tinnitus, comprising the steps of: generating electric signals that 
correspond to sounds for masking tinnitus; and directly stimulating a 
structure of a user by vibrating a device coupled to the structure, the 
device vibrating in response to the electric signals. 
Other features and advantages of the present invention will become apparent 
upon a perusal of the remaining portions of the specification and drawings 
.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
In the description that follows, the present invention will be described in 
reference to preferred embodiments. The present invention, however, is not 
limited to any specific embodiment. Therefore, the description the 
embodiments that follow is for purposes of illustration and not 
limitation. 
FIG. 1 illustrates an embodiment of the present invention. A signal 
generator 100 generates signals for a direct drive hearing device in order 
to mask tinnitus. The signal generator includes a multiple user adjustable 
controls 102,104,106,108,110, a battery compartment 112, and an integrated 
circuit (not shown). A battery is placed in the battery compartment in 
order to provide power to the signal generator. 
The adjustable controls allow a user to select characteristics of the 
signals that the signal generator produces, with the signal corresponding 
to sounds the user will perceive to mask the tinnitus. In one embodiment, 
adjustable control 102 allows a user to select the frequency of a primary 
tone. As the tinnitus sound is often a pure tone, the tinnitus sound may 
be masked by a signal that is 180.degree. out of phase with the tinnitus 
sound. In this manner, the tinnitus sound is effectively canceled out by 
the direct drive hearing device that receives a signal that is 180.degree. 
out of phase with the tinnitus sound. 
Adjustable control 104 allows a user to select the phase of the primary 
tone. By selecting the phase of the primary tone, the tinnitus may be more 
effectively masked. A user selects the intensity of signals produced by 
the signal generator with adjustable control 106. 
Some tinnitus sufferers hear multiple tones. A user is able to select the 
frequency of a secondary tone with control 108. Additionally, an 
adjustable control may be utilized to set the phase of the secondary tone. 
Thus, signals corresponding to a primary and secondary tone may be 
utilized to mask tinnitus. 
In other embodiments, the signal generator has controls that allow the user 
to select the bandwidth for the primary and secondary tones. The bandwidth 
controls direct the signal generator to produce a range of sounds around 
the user specified tone. For example, if a user selects a primary tone of 
1000 Hertz, the bandwidth control may direct the signal generator to 
produce tones in the range of 900-1100 Hertz. 
Some tinnitus sufferers find relief in listening to soothing background 
sounds like "white noise," rain, streams, waterfalls, surf, and the like. 
It is believed that these sufferers find relief because they are able to 
focus on the soothing background sounds and effectively "tune out" the 
tinnitus. Regardless of the reason, many tinnitus sufferers find relief 
from background sounds or noise. Adjustable control 110 allows a user to 
select the intensity of signals corresponding to background sounds. 
Additionally, an adjustable control may be utilized to select one of 
multiple background sounds stored in memory of the signal generator. 
Although the user adjustable controls are illustrated as screw-type 
mechanisms, the user adjustable controls manipulated by the user may also 
be in the form of dials, sliding mechanisms, switches, and the like. 
Additionally, embodiments of the signal generator may be fully implanted, 
the characteristics of the signals produced being set through magnetic 
switches or set prior to being implanted. 
FIG. 2 shows a block diagram of a tinnitus masker system utilizing a direct 
drive hearing device. The signal generator utilizes an integrated circuit 
200. The integrated circuit includes a pair of oscillators 202,204, a 
background signal generator 206, and an amplifier 208. Frequency controls 
210 and 211 determine the frequency of the signals generated by 
oscillators 202 and 204, respectively. Similarly, bandwidth controls 21 
and 213 determine the bandwidth of the signals generated by oscillators 
202 and 204, respectively. The frequency and bandwidth controls may be any 
number of known devices including pentiometers, variable resistors, and 
the like. 
Signals from the oscillators pass through a phase control 214 which may 
alter the phase of the signals generated by the oscillators. Once through 
the phase control, the signals are amplified or otherwise modified by an 
amplifier 208. For example, the amplifier may have an internal frequency 
which is subtracted from the frequency from the oscillators in order to 
produce a beat frequency which is in the range of human hearing. 
Additionally, the amplifier amplifies the signals from the background 
signal generator 206. An intensity (or amplitude) control 216 adjusts the 
intensity of the signals generated by the amplifier. 
An adjustment control 218 allows a user to select or otherwise alter the 
background signal generated by background signal generator 206. In one 
embodiment the adjustment control selects the intensity of the background 
noise. In another embodiment, the adjustment control allows the user to 
select the background signal generated. For example, the user may select 
white noise, rain, streams, waterfalls, or surf that are stored in a 
memory of the signal generator. In still another embodiment, both controls 
are utilized. 
A battery 220 provides power to the components of integrated circuit 200. 
The specific connections of the battery will vary depending on the 
components utilized; however, the battery is typically connected to all 
the components on the integrated circuit. In fully implanted embodiments, 
the battery may be rechargeable as through electromagnetic induction. 
Amplifier 208 produces a signal corresponding to sounds to mask tinnitus. 
The amplifier is coupled to a direct drive device 222. The amplifier may 
be directly electrically connected to the direct drive hearing device as 
shown or there may be intervening coils to transmit the signals across the 
user's skin as will be discussed in reference to FIG. 4. 
When used herein the term "direct drive hearing device" describes a hearing 
device that is attached or connected to a structure of a user so that 
vibration of the hearing device vibrates the structure resulting in 
perception of sound by the user. Typically, the direct drive hearing 
device is attached to a vibratory structure of the ear like the tympanic 
membrane, ossicles, oval window, or round window. However, direct drive 
hearing devices may also be attached to nonvibratory structures like the 
skull in order to stimulate hearing by bone conduction. 
In preferred embodiments, the direct drive hearing device is a floating 
mass transducer (FMT) device as is described in U.S. application Ser. No. 
08/582,301, filed Jan. 3, 1996, which is incorporated by reference for all 
purposes. A floating mass transducer device has a "floating mass" which is 
a mass that vibrates in direct response to an external signal which 
corresponds to sound waves. The mass is mechanically coupled to a housing 
which may be mounted on a vibratory structure of the ear. As the mass 
vibrates relative to the housing, the mechanical vibration of the floating 
mass is transformed into a vibration of the vibratory structure allowing 
the user to hear. 
Although preferred embodiments of the direct drive hearing device are 
floating mass transducer devices, other direct drive hearing devices may 
be utilized. For example, a direct drive hearing device may include a 
magnet attached to a vibratory structure which as driven by a coil 
anchored separately within the inner ear is described in U.S. Pat. No. 
5,015,225, issued May 14, 1991 to Maniglia et al., which is hereby 
incorporated by reference for all purposes. Additionally, a direct drive 
hearing device may include a electromechanical transducer having an outer 
tubing member having a bellows member attached to the end of the outer 
tubing member as described in U.S. Pat. No. 5,282,858, issued Feb. 1, 1994 
to Bisch et al., which is hereby incorporated by reference for all 
purposes. 
FIG. 3 shows an exemplary direct drive hearing device in the form of a 
floating mass transducer. Floating mass transducer 300 has a cylindrical 
housing 302. The housing has a pair of notches on the outside surface to 
retain or secure a pair of coils 304. The coils may be made of various 
metallic materials including gold and platinum. The housing retains the 
coils much like a bobbin retains thread. The housing includes a pair of 
end plates 306 that seal the housing. The housing may be constructed of 
materials such as titanium, iron, stainless steel, aluminum, nylon, and 
platinum. In one embodiment, the housing is constructed of titanium and 
the end plates are laser welded to hermetically seal the housing. 
Within the housing is a cylindrical magnet 308 which may be a SmCo magnet. 
The magnet is not rigidly secured to the inside of the housing. Instead, a 
biasing mechanism supports, and may actually suspend, the magnet within 
the housing. As shown, the biasing mechanism is a pair of soft silicone 
cushions 310 that are on each end of the magnet. Thus, the magnet is 
generally free to move between the end plates subject to the retention 
provided by the silicone cushions within the housing. Although silicone 
cushions are shown, other biasing mechanisms like springs and magnets may 
be utilized. 
When electrical signals corresponding to sound to mask tinnitus pass 
through coils 304, the magnetic field generated by the coils interacts 
with the magnetic field of magnet 308. The interaction of the magnetic 
fields causes the magnet to vibrate within the housing. Preferably, the 
windings of the two coils are wound in opposite directions to get a good 
resultant force on the magnet (i.e., the axial forces from each coil do 
not cancel each other out). The magnet vibrates relative to the housing 
within the housing and is biased by the biasing mechanism within the 
housing. The vibrations of the magnet cause the housing, and structures it 
is attached to, to vibrate. 
The resonant frequency of the floating mass transducer may be determined by 
the "firmness" by which the biasing mechanism biases the magnet. For 
example, if a higher resonant frequency of the floating mass transducer is 
desired, springs with a relatively high spring force may be utilized as 
the biasing mechanism. Alternatively, if a lower resonant frequency of the 
floating mass transducer is desired, springs with a relatively low spring 
force may be utilized as the biasing mechanism. 
It is known that an electromagnetic field in the vicinity of a metal 
induces a current in the metal. Such a current may oppose or interfere 
with magnetic fields. Although a thin metal layer such as titanium 
separates coils 304 and magnet 308, if the metal layer is sufficiently 
thin (e.g., 0.05 mm) then the electromagnetic interference is negligible. 
Additionally, the housing may be composed of a nonconducting material such 
as nylon. In order to reduce friction within the housing, the internal 
surface of the housing and/or the magnet may also be coated to reduce the 
coefficient of friction. 
FIG. 4 shows a cross-sectional view of a user's ear having an implanted 
tinnitus masker. An signal generator 400 generates signals to mask 
tinnitus. The signals are transmitted to an implanted receiver 402 by use 
of a coil within the signal generator. Receiver 402 includes a coil to 
receive the signals transcutaneously from the signal generator in the form 
of varying magnetic fields. As shown, the receiver is placed under the 
skin and converts the varying magnetic fields to electrical signals. A 
demodulator 404 demodulates the electrical signals which are transmitted 
to floating mass transducer 406 via leads 408. The leads reach the middle 
ear through a channel 410 that has been cut in the temporal bone during 
implantation of the floating mass transducer. 
Floating mass transducer 406 is attached to the incus by a clip. Other 
attaching mechanisms include bone cement, screws, sutures, and the like. 
During operation, the floating mass transducer vibrates in response to 
electrical signals corresponding to sounds to mask tinnitus. As the 
floating mass transducer is securely attached to a structure of the user 
(e.g., a vibratory structure), the vibrations are transmitted to the inner 
ear for the user to perceive the sounds. 
While the above is a complete description of preferred embodiments of the 
invention, various alternatives, modifications and equivalents may be 
used. It should be evident that the present invention is equally 
applicable by making appropriate modifications to the embodiments 
described above. For example, the above has shown that the signal 
generator is external; however, a signal generator may be implanted to 
form a fully implantable tinnitus masker system including a direct drive 
hearing device. Therefore, the above description should not be taken as 
limiting the scope of the invention which is defined by the metes and 
bounds of the appended claims along with their full scope of equivalents.