Electrical audio signal processing systems and devices – Hearing aids – electrical – Directional
Reexamination Certificate
1997-09-03
2001-04-03
Kuntz, Curtis A. (Department: 2743)
Electrical audio signal processing systems and devices
Hearing aids, electrical
Directional
C381S328000, C381S329000, C381S324000
Reexamination Certificate
active
06212283
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to audio and hearing devices. More particularly, the invention relates to hearing devices that are deeply inserted into the ear canal of an individual.
2. Description of the Prior Art
Inserting an articulated hearing device deeply into the ear canal of an individual is desirable for several reasons including cosmetic appeal and improved sound fidelity. However, due to the formidable design challenges presented by deep canal placement, including comfort of fit, ease of insertion and removal and unreliability of the flexible connection, flexible or articulated hearing devices are virtually unknown in the marketplace.
Anatomy and Morphology of the Ear Canal
FIGS. 1 and 2
show a cross-sectional anatomical view of the ear canal in the coronal and transverse planes of the head, respectively. The ear canal, for the purpose of this invention, can be described as having three segments. The first segment represents the medial concha cavity
20
just behind the tragus
21
, which is relatively large and is surrounded by cartilaginous tissue
22
. The second cavity
23
, medial to the aperture
24
of the external acoustic meatus
11
, is generally smaller and is also surrounded by cartilaginous tissue
22
. The third cavity
25
defines the final canal segment near the tympanic membrane
26
and is surrounded by dense bony tissue
27
. The tissue
28
lining the cartilaginous region
23
is relatively thick and has a well developed subcutaneous layer thus allowing some expansion to occur. In contrast, the tissue
29
lining the bony region
25
is relatively thin and therefore, little or no tolerance for expansion exists in this region. The cartilaginous region
23
is the major area of cerumen (ear-wax) production and accumulation in the ear canal.
The shape of a typical external ear canal, unlike that shown in most artistic renderings is rarely cylindrical or conical with a gradual narrowing towards the tympanic membrane. Instead, most ear canals are non-uniform with various levels of tortuous contours. Some canals have severe restrictions in the cartilaginous area. The ear canal is generally “S” shaped with a first bend
30
occurring approximately at the aperture of the ear canal and a second bend
31
at the cartilaginous-bony junction. The cross sectional diameter of the ear canal and the orientation of various regions within the canal are known to vary considerably from one individual to another. For example, the length from the aperture
24
to the lateral edge
32
of tympanic membrane
26
ranges from about 20 mm to about 25 mm. The cross-sectional shape is generally oval. The smallest diameter is generally in the bony region
25
in the transverse plane and ranges from about 4 mm to about 7 mm. The largest diameter is in the medial concha region
20
in the coronal plane and ranges from about 10 mm to about 18 mm.
The morphology of the ear canal reveals substantial deformation within the cartilaginous area
23
of the canal as a result of mandibular motion associated with talking, chewing, yawning, and biting. This deformation is generally caused by the asymmetric stresses from the actions of the mandibular condyle
33
on neighboring cartilaginous tissue. These deformations have radial components, e.g. constrictions, and axial components, i.e. inward and outward motion. These radial and axial deformations can generally be felt when one inserts a finger in the ear canal and moves the jaw. In one study, using magnetic resonance imaging (MRI), the deformation was shown to be as much as 25% in the anterior-posterior direction of the cartilaginous region of the canal (see, for example Oliveira, R. J., Hammer, B., Stillman, A., Holm, J., Jons, C., Margolis, R. H.,
A Look at Ear Canal Changes with Jaw Motion
, Ear and Hearing, Vol. 13, No. 6, 1992, pp. 464-466.)
The unique and tortuous nature of individual canals in combination with the dynamic canal deformations due to mandibular motion, present unsolved challenges to users of current hearing aids and other electroacoustic devices requiring deep insertion into the ear canal.
The Challenges of Deep Insertion of Hearing Devices into the Ear Canal
Inserting a receiver (speaker) deeply into the ear canal is desirable for hearing devices such as hearing aids or any earpiece for audio and communication applications. Close proximity of the receiver to the tympanic membrane improves the fidelity and efficiency of sound production. Deeper insertion also improves the external cosmetic appearance of the wearable device as it becomes less conspicuous.
In hearing aid design, articulating a receiver module within the ear canal is highly desirable in order to improve wearing comfort as well as maintain an acoustic seal at the receiver area of the hearing device. In conventional non-articulating hearing aid designs, the device must be “tightly” and precisely fitted in the ear canal in order to prevent sound leakage from the receiver (speaker) outlet of the device into the microphone inlet. These leakages cause acoustic feedback which is manifested by an annoying “whistling” sound. This “air-conducted” feedback is a common problem with many hearing aid users. Similarly, in earpieces for use with certain audio and communication devices, adequate sealing deep within the ear canal is required in order to provide fidelity and efficiency of sound production.
Because of the variability of shapes and sizes of ear canals as discussed above, and because a tight acoustic seal is required in order to prevent acoustic feedback, most hearing devices currently being marketed involve custom fabrication to ensure an “exact fit” of the earpiece to the canal of the individual. This custom process requires an impression of the ear canal, typically made by a dispensing professional. Subsequently a custom device or earmold is fabricated by the manufacturer according to the impression provided by the dispenser. The insertion and removal of the impression material within the deep portion of the ear canal is not only uncomfortable but potential complications due to hematoma or bleeding may occur (Gudmunsen, Gail,
Fitting CIC Hearing Aids-Some Practical Pointers
. The Hearing Journal, Vol. 47 , No. 7, pp. 46-47).
Unfortunately, even with custom earpieces or canal devices, canal deformations due to jaw movements lead to air gaps which are likely to cause feedback. For this reason, it is common for hearing aid users to remove the hearing device prior to eating in order to avoid the embarrassment of feedback during chewing or biting.
Another problem with the conventional hearing aid design is the “shell conduction” feedback caused by the common “shell” containing the receiver and the microphone of the device. This common housing facilitates the conduction of receiver vibrations to the microphone.
The State of the Art
Geib, et al. in U.S. Pat. Nos. 3,414,685 (see FIG. 5.) and 3,527,901 (see FIG. 8) describe a hearing device with a receiver member connected to a main compartment via a flexible link. McCarrel et al. in U.S. Pat. No. 3,061,689 disclose a hearing aid with a receiver connected to hearing aid via a “coupling member being formed of resilient and flexible material” (see FIG. 1). Martin et al. in U.S. RE 26,258 (see FIG. 3) disclose a miniaturized hearing aid “providing pivotal connection between the receiver member and the housing,” and “The elongated receiver member is mounted inside of the hollow resilient boot.”
The above inventions provide a resilient connection in order to provide flexibility in the orientation of the receiver within the ear canal. However, a resilient connection by nature is unduly limited in its range of motion and has a considerable bias for a centering position. Furthermore, the electrical wiring contained within the flexible joint is likely to experience damage with use due to the stress of flexing. The above inventions do not teach a rigid yet articulated joint for fit and comfort while providing protection to the interconnecting electrical wiring moving within.
Adelma
Fletcher Henry
Shennib Adnan
Sorensen Jorgen
Urso Richard C.
Decibel Instruments, Inc.
Glenn Michael A.
Harvey Dionne N.
Kuntz Curtis A.
Peil Christopher
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