Extended wear canal hearing device

Details Extended wear canal hearing device Extended wear canal hearing device

1999-06-08

2002-10-29

Kuntz, Curtis (Department: 2643)

Electrical audio signal processing systems and devices

Hearing aids, electrical

Specified casing or housing

C381S322000, C381S323000, C381S324000, C381S329000

Reexamination Certificate

active

06473513

ABSTRACT:

BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to hearing devices, and, more particularly, to miniature hearing devices that are deeply positioned in the ear canal for improved energy efficiency, sound fidelity, and inconspicuous extended wear.
B. Description of the Prior Art
Brief Description of Ear Canal Anatomy
The external acoustic meatus (ear canal) is generally narrow and contoured as shown in the coronal view in FIG.
1
. The ear canal
10
is approximately 25 mm in length from the canal aperture
17
to the center of the tympanic membrane
18
(eardrum). The lateral part (away from the tympanic membrane) of the ear canal, a cartilaginous region
11
, is relatively soft due to the underlying cartilaginous tissue. The cartilaginous region
11
of the ear canal
10
deforms and moves in response to the mandibular (jaw) motions, which occur during talking, yawning, eating, etc. The medial (towards the tympanic membrane) part, a bony region
13
proximal to the tympanic membrane, is rigid due to the underlying bony tissue. The skin
14
in the bony region
13
is thin (relative to the skin
16
in the cartilaginous region) and is more sensitive to touch or pressure. There is a characteristic bend
15
that roughly occurs at the bony-cartilaginous junction
19
(referred to herein as the bony junction), which separates the cartilaginous
11
and the bony
13
regions. The magnitude of this bend varies among individuals.
A cross-sectional view of the typical ear canal
10
(
FIG. 2
) reveals generally an oval shape and pointed inferiorly (lower side). The long diameter (D
L
) is along the vertical axis and the short diameter (D
S
) is along the horizontal axis. Canal dimensions vary significantly among individuals as shown below in the section titled Experiment.
Hair
5
and debris
4
in the ear canal are primarily present in the cartilaginous region
11
. Physiologic debris includes cerumen (earwax), sweat, decayed hair, and oils produced by the various glands underneath the skin in the cartilaginous region. Non-physiologic debris consists primarily of environmental particles that enter the ear canal. Canal debris is naturally extruded to the outside of the ear by the process of lateral epithelial cell migration (see. e.g., Ballachanda,
The Human ear Canal,
singular Publishing, 1995, pp. 195). There is no cerumen production or hair in the bony part of the ear canal.
The ear canal
10
terminates medially with the tympanic membrane
18
. Laterally and external to the ear canal is the concha cavity
2
and the auricle
3
, both also cartilaginous. The junction between the concha cavity
2
and the cartilaginous part
11
of the ear canal at the aperture
17
is also defined by a characteristic bend
12
known as the first bend of the ear canal.
Several types of hearing losses affect millions of individuals. Hearing loss particularly occurs at higher frequencies (4000 Hz and above) and increasingly spreads to lower frequencies with age.
The Limitations of Conventional Canal Hearing Devices
Conventional hearing devices that fit in the ear of individuals generally fall into one of 4 categories as classified by the hearing aid industry: (1) Behind-The-Ear (BTE) type which is worn behind the ear and is attached to an ear mold which fits mostly in the concha; (2) In-The-Ear (ITE) type which fits largely in the auricle and concha cavity areas, extending minimally into the ear canal; (3) In-The-canal (ITC) type which fits largely in the concha cavity and extends into the ear canal (see Valente M.,
Strategies for Selecting and Verifying Hearing Aid Fittings,
Thieme Medical Publishing. pp. 255-256, 1994), and; (4) Completely-In-the-Canal (CIC) type which fits completely within the ear canal past the aperture (see Chasin, M.
CIC Handbook,
Singular Publishing (“Chasin”), p. 5, 1997).
The continuous trend for the miniaturization of hearing aids is fueled by the demand for invisible hearing products in order to alleviate the social stigma associating hearing loss with aging and disability. With continued improvements in miniaturization of hearing aid components, the battery has emerged as the largest single component in canal hearing devices (ITC and CIC devices are collectively referred to herein as canal devices or canal hearing devices). The conventional battery, button-cell type, remains predominantly used in virtually all hearing aid devices.
In addition to the cosmetic advantage of canal devices, there are actual acoustic benefits resulting from the deep placement of the device within the ear canal. These benefits include improved high frequency response, less distortion, reduction of feedback and improved telephone use (Chasin, pp. 10-11).
However, even with advances leading to the advent of canal devices, there remains a number of fundamental limitations associated with the underlying design and configurations of conventional canal device technology. These problems include: (a) frequent device handling, (b) oscillatory (acoustic) feedback, (c) custom manufacturing and impression taking, (d) energy inefficiency, (e) space inefficiency related to current battery designs, and (f) occlusion related problems. These limitations are discussed in more detail below.
(a) Frequent device handling: Conventional canal devices require frequent insertion and removal from the ear canal. Manufacturers often recommend daily removal for cleaning and maintenance of the CIC device (see, e.g.,
Users's Instructions, SENSO CIC and Mini Canal
, Widex Hearing Aid Co. February 97, pp. 11, 16; and
General Information for Hearing aid Users
, Siemens Hearing Instruments, Inc. March 98, p. 8). Daily removal of conventional CICs is also required for relieving the ear from the pressures of the device occluding the cartilaginous region. Furthermore, CIC hearing aid removal is also required in order to replace the conventional button-cell battery, typically lasting less than 2 weeks. The manual dexterity required to manipulate a canal device or replace a conventional battery, daily, poses a serious challenge to many hearing impaired persons who are elderly. These individuals typically suffer from arthritis, tremors, or other neurologic problems that limit their ability to frequently handle a miniature hearing aid.
(b) Oscillatory feedback occurs when leakage (arrows
32
and
32
′ in
FIG. 3
) from sound output
30
, typically from a receiver
21
(speaker), occur via a leakage path or a vent
23
. The leakage (
32
′) reaches a microphone
22
of a canal hearing device
20
causing sustained oscillation. This oscillatory feedback is manifested by “whistling” or “squealing” and is not only annoying to hearing aid users but also interferes with their communication. Oscillatory feedback is typically alleviated by tightly occluding (sealing) the ear canal. However, due to imperfections in the custom manufacturing process (discussed below) or to the intentional venting incorporated within the hearing device (also discussed below) it is often difficult if not impossible to achieve the desired sealing effect, particularly for the severely impaired who require high levels of amplification. Oscillatory feedback typically occurs at high frequencies due to the presence of increased gain at these frequencies.
(c) Custom manufacturing and impression taking Conventional canal devices are custom made according to an impression taken from the ear of the individual. A canal device housing
25
(FIG.
3
), known as shell, is typically custom fabricated according to an individual impression to accurately assume the shape of the individual ear canal. Customizing a conventional canal device is presumed required in order to minimize leakage gaps, which cause feedback, and also to improve the comfort of wear. Custom manufacturing is an imperfect process, time consuming and results in considerable cost overheads for the manufacturer and ultimately the hearing aid consumer (user). Furthermore, the impression taking process itself is often uncomfortable for the user.
(d) Energy ineffici

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