Surgery – Diagnostic testing – Ear or testing by auditory stimulus
Reexamination Certificate
1999-04-02
2001-10-09
Brown, Michael A. (Department: 3764)
Surgery
Diagnostic testing
Ear or testing by auditory stimulus
C073S585000
Reexamination Certificate
active
06299584
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates generally to hearing test devices and more specifically to an infant hearing screener which uses distortion-product otacoustic emissions (DPOAE) to determine the function of the outer hair cells, which is an indication of middle-ear function. For example, the absence of DPOAE indicates a possible hearing loss.
The otacoustic emissions produced by a healthy ear are extremely small in magnitude. The emissions typically range from −10 db SPL to +20 db SPL. Any kind of extraneous noise introduced into the ear canal or measurement system can mask these emissions and give a false negative response. The microphone must have a very low internal noise level to discriminate the emissions from the system noise. All existing equipment for testing for DPOAE uses a probe which seals into the ear canal and is attached to the measurement equipment through a cable. This type of system is not practical in an infant screener for several reasons.
These reasons include the fact that an infant's ear canal is very small, and as a result, it can be quite difficult to seal a probe into such a small canal. Any pull on the probe from the attached cable can break the seal or pull the probe out of the canal. In addition, the time required to place a probe in the infant's ear canal significantly slows down the testing process. Typically, the infant is asleep when the testing is performed so that movement is minimal. The process of putting the probe into the infant's ear canal in a manner so that it stays for the duration of the test often wakes the infant which, of course makes the test difficult or impossible to perform.
While a hand-held screening device alleviates many of the above discussed problems, implementation of such a device has inherent problems which must be overcome to provide an effective hearing measurement device. One such problem results from the vibrational noise generated by the tester's hand during the testing. This noise is transmitted through the device and into the microphone which prevents accurate measurements. Holding a conventional probe to the ear canal creates a noise level that completely masks any emissions that could otherwise be detected.
Another problem is the difficulty in achieving a consistent seal to the infant's ear canal. Difficulty in maintaining the seal results from minor movements of the infant's head and/or the tester's hand. An embodiment of the screener solves the above problems, thereby providing a screener for performing DPOAE testing quickly and easily.
BRIEF SUMMARY OF THE INVENTION
The present invention is an infant hearing screener which uses distortion-product otacoustic emissions (DPOAE) to determine the function of the outer hair cells within the middle ear structure. The function of the outer hair cells is an indication of middle-ear function; the absence of DPOAE indicates a possible hearing loss.
The infant screener is hand-held device that couples to the infant's ear to perform DPOAE testing. The device creates tones and administers them to the ear canal through two receivers. The emissions are then picked up through a low-noise microphone, and analyzed by a built-in digital signal processor (DSP). The result is displayed on a liquid crystal display (LCD) and can be printed by infrared link to a separate hand-held printer.
The infant screener uses a different approach for sealing to the ear canal that solves the problems in prior devices listed above. This design has a testing probe mechanically attached to the measurement system making a single hand-held device that is partially inserted directly into the infant's ear canal. Such an arrangement negates the need for an external cable interconnection.
An embodiment of the screener includes an assembly to maintain sealing contact in the ear canal. In addition, the screener includes a vibrational noise isolating microphone assembly. In an embodiment, the screener isolates noise generated by the slight tremor and movement that typically results in a normal human hand.
To this end, the tester can hold the hearing testing device to the ear canal and vibrational noise is isolated by attaching the microphone assembly to the hand-held instrument with a mesh of compliant elastomer o-rings. The o-rings are coupled to the microphone housing in a circular pattern designed to give the microphone assembly movement on all axes. The vibrational noise generated by the hand is thereby damped through the o-rings. This formation minimizes the induced vibrational noise that is transmitted into the microphone assembly.
In addition, maintaining a good seal to the ear canal is critical to the ability to measure otacoustic emissions. This is made easier by the screener which allows movement of the ear tip on the x and y axis. The screener also helps achieve the proper pressure on the entrance of the ear canal to effect the sealing and prevent uncomfortable pressures.
An embodiment of the screener includes an assembly of o-rings which hold the microphone and ear tip assembly to the isolation mechanism described above. These o-rings flex to allow the tip to move and keep it centered within the isolation mechanism. The amount of flex in the o-rings determines the ease of movement and can be manipulated by choosing o-rings of different materials and different durometer. This selection process is important because choosing the right material will allow for a consistent and comfortable pressure on the ear canal even when there are slight movements of the tester's hand, or of the patient's head.
When measuring otacoustic emissions it can be difficult to know what noise is in the ear canal and what the source of the noise is. The two possible sources of the noise are biological and environmental. The infant hearing screener allows the user to listen to the noise level in the ear canal before testing and between tests. Doing so gives the tester the feedback necessary to know how to hold the screener against the patient's ear and how much pressure is necessary to maintain the seal at the entrance of the ear canal. The user can also listen to the actual emissions generated by the ear.
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Distortion-Product OAE Analysis: Is It Ready For Broad Clinical Use?, By John D. Durrant, The Hearing Journal/Nov. 1992, vol. 45, No. 11.
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Brown Michael A.
Etymotic Research Inc.
McAndrews Held & Malloy Ltd.
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