Download Implementation of a Medical Device for Testing the Functionality of

Implementation of a Medical Device for Testing
the Functionality of the Ear in Newborns
Onyinyechi C. Ibeneche
Department of Electrical Engineering
Clarkson University, Potsdam NY
Being able to assess the health of the human auditory system is of utmost importance where infants
are concerned, especially newborn babies. In the United States, every year over thirty children are
born with a hearing disability [5]; a late determination of hearing impairment can have grave effects
on a child’s literary and linguistic ability [6]. In addition to this, studies show that about 30% of
hearing impairment in children occurs in the infantile years, after their birth. School-age children
are tested annually for hearing and vision impairments, however children in preschool do not
receive the same treatment [5]. It would be ideal for such children to be tested at the Pediatricians
office. The problem with this however, is that existing methods of testing for hearing impairments
must be conducted in special noise-proof surroundings [7]. This poses a problem for conducting
such tests during a child’s preschool years. The aim of this project is to eliminate this necessity of a
noise proof environment, as it seeks to implement a clinically viable medical device that can
determine the functionality of the human ear, regardless of a noisy surrounding.
Information about the functionality of the ear can be obtained using acoustic measurements in the
ear canal. Biomedical researchers have discovered that if special acoustic stimuli, in the form of
two pure tones, are sent into the ear, otoacoustic emissions can be obtained from the sensory hairs
in the cochlea [1]. Distortion Product Otoacoustic Emissions (DPOAEs) are very low-level
stimulated acoustic responses to two pure tones sent into the ear canal (at frequencies, f1 and f2).
These responses are very faint sounds emitted during acoustic stimulation. Due to the fact that the
ear is a non-linear structure, a number of these low level distortion products are generated in
response to the two pure tones, as a result of the inter-modulation process that occurs within the
cochlea. Of these otoacoustic emissions, researchers are interested in the response that occurs at a
frequency of 2f1-f2. This frequency usually yields the strongest otoacoustic emission, and is
generally taken to be the measure of the functionality of the ear [2].
To Graduate: Dec 2004
Mentor: Alireza K. Ziarani
Clarkson University Honors Program
Oral Presentation
DPOAEs provide an objective, non-invasive method to test for the functionality of the ear.
Presently, DPOAE measurements are conducted using acoustic probes, in the form of a speaker and
microphone, inserted in the ear. The resulting information is then processed offline in the
MATLAB environment using conventional signal processing techniques such as the Fast Fourier
Transform (FFT) with averaging [1]. This method necessitates the conduction of the process in two
stages being
(i)
Data collection
(ii)
Data processing
The process is also highly unreliable in noisy environments and as such requires complex signal
processing techniques to extract the desired signal in addition to a relatively noise proof
environment for data collection [1]. As mentioned before, these DPOAE are very faint sounds
emitted during acoustic simulation, and as such they are very difficult to extract from
collected data. Presently, the data collection is performed in a variety of equally efficient
methods, involving acoustic probes inserted in the ear. Subsequently, the data is processed
in the MATLAB environment. Herein lies the playing field for researchers. Numerous
signal processing techniques have been suggested, and utilized, to process the collected
data. The emphasis is always on reducing the method complexity and the processing time.
This project attempts to annul the aforementioned problems associated with DPOAE measurement
devices by implementing a clinically viable prototype. The gap between data collection and data
processing will be bridged using the MATLAB data acquisition toolbox. The problem associated
with complex computation, the need for a sound proof environment and long measurement time
will be resolved by employing a novel signal processing algorithm, developed by Alireza K.
Ziarani, that is highly immune to noise and hence takes a relatively short time to extract a signal
buried under noise [3]; this algorithm already exists as a Simulink model, and, consequently,
MATLAB will be used as the signal processing environment.
To Graduate: Dec 2004
Mentor: Alireza K. Ziarani
Clarkson University Honors Program
Oral Presentation
The following is a generalized diagram of the aforesaid process.
Due to the absence of the probes for data collection, the progress of the project has been retarded.
However, pre-recorded data has been utilized to attain the expected DFT of the final results. The
diagram depicts the two pure tones at frequencies f1 and f2, and the resultant DPOAE at 2f1-f2.
The other components of the signal are a combination of the noise and other distortion products
generated by the ear.
The extraction of the DPOAE with the employed algorithm is indeed faster than conventional
methods; the signal being acquired at an average of one to two seconds, whereas other methods
may take ten to fifteen seconds. However the entire process has failed to achieve the ideal of
being conducted in real time as there is a short, but necessary, time lapse as the data is transferred
from the MATLAB to Simulink environment. This lapse may be avoided if the algorithm is
converted to MATLAB code.
To Graduate: Dec 2004
Mentor: Alireza K. Ziarani
Clarkson University Honors Program
Oral Presentation
References
[1]
A.K. Ziarani and A.Konrad, “A Novel Method of Estimation of DPOAE Signals,” to
appear in IEEE Trans. Engineering in Medicine and Biology Society.
[2]
L.A. Christensen and M.C. Killion, “A Pass/Refer Criterion for Screening Newborns Using
DPOAEs,” Presented at the International Evoked Response Audiometry Study Group, XVI
Biennial Symposium Tromso, Norway May 30- June 3, 1999.
[3]
A.K. Ziarani, A. Konrad and I.M. Blumenfeld, “Experimental Verification of A Novel
Method of Extraction of Nonstationary Sinusoids. IEEE Trans. Circuits and Systems, Vol.
1, pp 455-558, Aug 2002.
[4]
A. Gluzmann and H. Kunov, “On the Use of a 16-bit Multimedia Sound Board in a Virtual
Instrument for Hearing Assessment,” IEEE Trans. Engineering in Medicine and Biology
Society, Vol. 2, pp 1609-1610, Sep. 1995.
[5]
National Institute on Deafness and Other Communication Disorders (NIDCD), National
Strategic Research Plan: Hearing and Hearing Impairment, Bethesda, MD: HHS, NIH,
1996.
[6]
M. Feinmesser, L. Tell and H. Levi, “Follow-up of 40,000 infants screened for hearing
defect,” Audiology, Vol. 21, pp. 197-203, 1982.
[7]
National Institute on Deafness and Other Communication Disorders (NIDCD) Working
Group on Early Identification of Hearing Impairment, Communicating the Need for
Follow-up to Improve Outcomes of Newborn Hearing Screening, Bethesda, MD: HHS,
NIH, 2001.
To Graduate: Dec 2004
Mentor: Alireza K. Ziarani
Clarkson University Honors Program
Oral Presentation