Electrical audio signal processing systems and devices – Hearing aids – electrical – Specified casing or housing
Reexamination Certificate
1998-10-28
2002-10-29
Kuntz, Curtis (Department: 2643)
Electrical audio signal processing systems and devices
Hearing aids, electrical
Specified casing or housing
C381S322000, C381S328000
Reexamination Certificate
active
06473512
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention relates to an ear-worn device that is comprised of a soft yet solid elastomer corpus for use in custom in-the-ear hearing products. The degree of stiffness of this soft-solid material preferably ranges from negligible to forty points, Durometer Hardness, Shore A. Specifically, the present invention relates to a system and method for producing a custom soft yet solid elastomer hearing product yielding greater comfort and superior acoustic performance for the hearing instrument wearer. Additionally, this product will provide solutions to a population with whom traditional custom in-the-ear technology was unsuccessful. By the nature of its soft design this product will have improved compliance and elasticity, thereby better accommodating the dynamic nature and the anatomical variants of the external ear canal. This invention will also relate to future applications in the field of mass communications, such as an ear-worn digital telephone or a two-way radio system.
II. General Background of the Invention
The Hearing Instrument Industry combines electro-acoustic technology with custom prosthetic design to ergonomically couple a hearing instrument to the human ear in a cosmetically acceptable manner. The industry has realized major electronic advancements in hearing instrument technology. With miniaturization of electronic components the standard instrument design evolved from a table worn unit, using vacuum tubes in the nineteen twenties, to a wearable body worn unit in the late nineteen thirties. The introduction of transistors in the nineteen fifties made the behind-the-ear (BTE) hearing instrument possible. As integrated circuits were developed, the custom in-the-ear (ITE) instrument became a reality. On-going electronic developments surrounding the hearing instrument industry have resulted in the micro-miniaturization of electronic components. This miniaturization has culminated in the introduction of “deep insertion technology”, manifested as the completely-in-the-canal (CIC) hearing instrument, which is totally contained within the ear canal and is virtually invisible. As a consequence, hearing instruments have increased signal processing capabilities, yet require very limited physical space.
With the development of programmable hearing instruments, using either analog or digital signal processing, custom electronic design has shifted from the manufacturing level to the clinical level. That is, the clinician can now customize the electro-acoustic response of the instrument to match the degree of hearing loss via programmable software. It is no longer necessary for the device to be returned to the manufacturer for hardware changes to achieve the desired electro-acoustic characteristics.
In direct contrast to electronic advances within the industry, little or no advancement has been realized in custom prosthetic design. Since the late nineteen sixties, when the custom instruments were developed, the materials and the construction techniques have remained virtually unchanged. These materials and techniques were adopted from the dental industry, whereby the customized housing—commonly called a “shell”—was constructed using acrylic with a ninety point “D” Shore Hardness. Typical molding of the dental acrylate involves making a female silicone cavity from the original ear impression. This female cavity is then filled with liquid acrylate and cured using an ultraviolet light of known intensity across a known time period to cure only the outer most material forming a wall or a shell. This process is very similar to ceramics. The shell is then removed from the female cavity, decked down in the sagittal plane, drilled for vents and receiver bores, polished and then mounted with a faceplate containing the electro-acoustic circuitry. The end result is a hollow glass-like plastic replica of the external ear canal. The finished shell's primary function is to house the delicate electronic components. Yet, a material of this hardness, worn deeply in the human ear canal, brings forth the issues of comfort and acoustic performance.
When the acrylic shell was introduced, hearing instruments were worn in a relatively elastic cartilaginous portion of the ear canal. However, the current trend for hearing instrument placement is to position the device into the bony portion of the ear canal extending three millimeters medially from the second directional bend previously defined as “deep insertion technology”. To illustrate the implications of this technology, the anatomy and physiology of the ear will be reviewed.
Anatomically, the ear canal is defined as the area extending from the concha to the tympanic membrane. It is important to note that the structure of this canal consists of elastic cartilage laterally, and porous bone medially covered by skin. The cartilaginous portion constitutes the outer one third of the ear canal. The medial two-thirds of the ear canal is osseous or bony and is oriented forward and downward making it slightly concave as compared to the more cylindrical cartilaginous portion. The average canal is approximately twenty-five millimeters in length but is as much as six millimeters longer on the anteroinferior wall of the osseous canal. The skin of the osseous canal, measuring only two-tenths of a millimeter (0.2 mm) in thickness, is much thinner than the skin of the cartilaginous canal, measuring five-tenths to one millimeter (0.5 to 1 mm) in thickness. The difference in thickness directly corresponds to the presence of apocrine (ceruminous) and sebaceous glands found only in the fibro-cartilaginous area of the canal. This thinly skinned, thinly lined area of the bony canal is extremely sensitive to any hard foreign body, such as an acrylic hearing instrument.
Physiologically, the ear canal is dynamic in nature. It is geometrically altered by mandibular action and by head position changes. These cause alternating elliptical elongation and widening of the ear canal. These alterations in canal shape vary widely, not only from person to person, but also from ear to ear.
Applying hard, hollow, acrylic hearing instrument technology to the external ear canal has numerous limitations. Because of the rigid nature of the acrylic shell of many traditional instruments, they are difficult to insert beyond the second directional canal bend. The difficulty of insertion is increased in the presence of any anatomical variant such as a stenotic canal, a bulbous canal, or a tortuous canal.
Because of the rigid nature of the acrylic shell of many traditional instruments, they must pivot in reaction to mandibular action or head movement, thereby changing the angle of attack of the receiver toward the tympanic membrane resulting in a distorted acoustic response.
Additionally, this pivoting action often causes displacement of the entire instrument causing a slit leak between the wall of the device and the wall of the ear canal. That leak creates an open acoustic loop between the receiver and the microphone of the instrument resulting in an electro-acoustic distortion commonly known as feedback.
Because of the rigid nature of the acrylic shell, some deeply inserted traditional instruments will exert pressure upon the bony portion of the ear canal when mandibular action or head movement cause the instrument to pivot.
Because of the hollow nature of the acrylic shell, many traditional instruments cannot protect the internal components from damage due to shock (i.e. the impact suffered by a traditional instrument dropped onto a hard surface).
Because of the hollow nature of the acrylic shell, many traditional instruments provide an air-conducted feedback loop from the receiver to the microphone.
Because of the hollow nature of the acrylic shell and the inherent necessity to suspend the receiver by tube mounting, the traditional instrument is prone to collection of cerumen in the receiver tub
Creel Lynn P.
Desporte Edward J.
Juneau Roger P.
Kinler Kelly M.
Major Michael
Dabney P.
Garvey Charles C.
Garvey, Smith, Nehrbass & Doody, L.L.C.
Kuntz Curtis
Nehrbass Seth M.
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