Surgery – Surgically implanted vibratory hearing aid
Reexamination Certificate
1997-08-07
2001-07-24
Dvorak, Linda C. M. (Department: 3739)
Surgery
Surgically implanted vibratory hearing aid
C607S055000
Reexamination Certificate
active
06264603
ABSTRACT:
THE FIELD OF THE INVENTION
This invention relates generally to at least partially implantable hearing assistance systems, and more particularly to the sensing of sound vibrations in the middle ear.
BACKGROUND
Some types of partial middle ear implantable (P-MEI), total middle ear implantable (T-MEI), cochlear implant, or other hearing assistance systems utilize components disposed within the middle ear or inner ear regions. Such components may include an input transducer for receiving sound vibrations or an output stimulator for providing mechanical or electrical output stimuli corresponding to the received sound vibrations.
An example of such a device is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaefer on Mar. 8, 1988. In the '366 patent, a mechanical-to-electrical piezoelectric input transducer is associated with the malleus bone in the patient's middle ear. The malleus vibrates in response to sounds received at the patient's tympanic membrane (eardrum). The piezoelectric input transducer transduces mechanical energy of malleus vibrations into an electrical signal, which is amplified and further processed by an electronics unit. A resulting electrical signal is provided to an electrical-to-mechanical piezoelectric output transducer that generates a mechanical vibration coupled to an element of the ossicular chain or to the oval window or round window. In the '366 patent, the ossicular chain is interrupted by removal of the incus. Removal of the incus prevents the mechanical vibrations delivered by the piezoelectric output transducer from mechanically feeding back to the piezoelectric input transducer.
Hearing assistance systems that sense sounds through corresponding ossicular vibrations face numerous difficulties. For example, the direction of motion of malleus vibrations varies unpredictably between individuals, making such vibrations difficult to transduce into a corresponding electrical signal, since sensors that transduce such vibrations typically perform optimally if the motion of the vibrations is in a particular direction. For example, a cantilevered piezoelectric bimorph input transducer provides a maximum output electrical signal amplitude when the direction of motion of the vibrations is perpendicular its longitudinal direction. A further complication is that the direction of motion of the malleus vibrations may be frequency dependent. As a result, an input transducer that is optimally positioned to sense malleus vibrations at a particular frequency in the audio frequency range may be inadequately positioned to sense malleus vibrations at a different frequency in the audio frequency range. There is a need in the art to provide sensing of sound vibrations in the inner ear, in which any variability in direction of motion of ossicular or other auditory elements is accommodated.
SUMMARY
The present invention includes a sensor for use with an at least partially implantable hearing assistance system. The sensor transduces a mechanical vibration of an auditory element into an electrical signal. A first input transducer is proportioned for transducing a first directional component of the mechanical vibration into a first electrical signal. A second input transducer is proportioned for transducing a second directional component of the mechanical vibration into a second electrical signal. The first and second input transducers are arranged such that the first and second directional components of the mechanical vibration are nonidentical. In one embodiment, a third input transducer is proportioned for transducing a third directional component of the mechanical vibration into a third electrical signal, such that the first, second, and third directional components of the mechanical vibration are nonidentical and linearly independent. The sensor is used in or with a hearing assistance system having an electronics unit that receives the electrical signals from the transducers, and provides a resulting combined electrical signal in response thereto.
The hearing assistance system also provides a method of transducing a mechanical vibration of an auditory element into at least one electrical signal. A first input transducer is positioned to transduce a first directional component of the mechanical vibration into a first electrical signal. A second input transducer is positioned to transduce a second directional component of the mechanical vibration into a second electrical signal. The first and second directional components of the mechanical vibration are nonidentical.
In one embodiment, the first and second electrical signals are combined. A first method of combining the first and second electrical signals squares each signal to provide resulting squared signals, sums the resulting squared signals to provide a sum-of-squares signal, and performs a square root function upon the resulting sum-of-squares signal to provide a resulting combined electrical signal. A second method of combining the first and second electrical signals individually filters the first and second electrical signals to provide resulting filtered signals, and sums the filtered signals to provide a resulting combined electrical signal. A third method of combining the first and second electrical signals differentiates the second electrical signal to provide a second differentiated electrical signal, and sums the second differentiated electrical signal with the first electrical signal to provide a resulting combined electrical signal.
In one embodiment, a third input transducer is positioned to receive a third directional component of the mechanical vibration. In this embodiment, the first, second, and third directional components of the mechanical vibration are nonidentical and linearly independent. The first, second, and third electrical signals are combined, such as by the above-described techniques. In one embodiment, the hearing assistance system includes an external programmer for adjusting hearing assistance parameters in a hearing assistance device and for data transmission from the hearing assistance device to the programmer, such as for parameter verification or diagnostic purposes. For example, the external programmer selects between the above-described signal combination techniques, in one embodiment of the present invention.
Thus, the present invention provides an improved hearing assistance system for sensing sound vibrations in the middle ear. The hearing assistance system accommodates variability in the direction of motion of an ossicular or other auditory element. This is particularly advantageous for sensing mechanical vibrations of an auditory element where the exact direction of the mechanical vibrations may be unknown, variable, or difficult to determine.
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Dvorak Linda C. M.
Fredrikson & Byron , P.A.
Kearney R.
St. Croix Medical, Inc.
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