Surgery – Diagnostic testing – Ear or testing by auditory stimulus
Patent
1999-01-29
2000-10-31
O'Connor, Cary
Surgery
Diagnostic testing
Ear or testing by auditory stimulus
73585, A61B 500
Patent
active
061395072
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed toward a system and apparatus for accurately and rapidly measuring acoustic power flow at various points within the human ear canal.
2. Description of Related Art
In the field of audiology the chief objective of most diagnostic tools is to obtain an accurate measurement of wide band, middle ear power flow as estimated from the ear canal power flow. Power flow per unit area is known as acoustic intensity. An accurate reading of acoustic intensity is necessary for improved clinical diagnosis with respect to pathologies of the human auditory system. Accuracy alone, however, is insufficient to provide a clinically acceptable diagnostic system. The measurements must be obtainable rapidly and in a cost-efficient manner. Thus, the goal of the present invention is to provide a cost efficient, rapid, and accurate system of obtaining an acoustic intensity measurement within the human auditory system. Such a system will provide, inter alia, significant benefits in hearing screening programs leading to earlier discovery of ear pathologies.
Diagnostic tools such as air conduction audiometry, bone conduction audiometry, evoked response audiometry, and evoked otoacoustic emissions are critically dependent on an accurate measurement of the acoustic sound field. More specifically, acoustic intensity is a desirable measurement. Acoustic intensity is a measurement of the power flow per unit area. Unfortunately, measuring intensity directly is extremely difficult.
A more easily obtainable measurement is that of sound pressure as opposed to acoustic intensity. Pressure instruments are widely used in audiology. Pressure, however, only yields an intensity estimate when no standing waves are present, i.e., when power is flowing in one direction only, namely in sound fields that do not have acoustic reflection components. In sound fields having acoustic reflection components, standing waves will be produced and a pressure measurement is ineffective.
When reflections are not present, power flow is proportional to the square of the pressure multiplied by the area along the ear canal. In a calibrated pressure field having no reflection, power can be independent of frequency. However, when reflections are present in the ear canal then canal impedance is a finction of location in the ear canal, even if the pressure field is calibrated. In this case the square of the pressure does not characterize power flow. Sound pressure and acoustic intensity have a complex relationship when reflections are present in the ear canal. Thus, a single pressure measurement cannot determine the acoustic power flow in the ear canal unless the source transducer has been characterized. The source transducer is a small loud speaker/receiver combination placed in the ear canal. At least two independent measurements are necessary to do this. Characterization requires determining the source transducer's open-circuit pressure and its source impedance. Use of pressure as a measure of signal strength does not, however, take into consideration the source transducer open-circuit pressure or the source transducer impedance and thus cannot determine actual acoustic intensity in an ear canal having standing waves due to reflection.
In the early days of audiometry (circa 1930), sound levels were calibrated in a free-field (i.e. a field free of standing waves) where sound pressure and acoustic intensity are equivalent. Supra-aural headphones soon became popular because of their increased ease of use, acoustic isolation, and reduced low frequency calibration variability. These headphones were typically calibrated with a standardized acoustic coupler (i.e., artificial ear). This method of calibration improperly assumed that the acoustic impedance of the coupler was essentially the same as that of the ear being tested. As a result, considerable difficulty was encountered in developing a practical, yet reasonable way of accurately specifying hearing loss. One practical problem that emerge
REFERENCES:
patent: 5105822 (1992-04-01), Stevens et al.
patent: 5197332 (1993-03-01), Shenib
patent: 5526819 (1996-06-01), Lonsbury-Martin
Voss and Allen, Measurement of Acoustic Impedance and Reflectance in the Human Ear Canal, J.Acoust.Soc.Am 95(1), Jan. 1994.
Miomsa Acoustics Inc.
Nissim Stuart H.
O'Connor Cary
Wingood Pamela
Woodbridge Richard C.
LandOfFree
Method and apparatus for measuring acoustic power flow within an does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for measuring acoustic power flow within an, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for measuring acoustic power flow within an will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2045855