Operating Instructions
2
subsequent printing. The results are displayed via the display on the front of the device and are stored
in the device’s internal memory. After testing is completed, results can be printed using the
optional
thermal paper printer or the default PC printer via software interface. Tests can also be exported to a
computer database via optional software. Test results are stored in the non-volatile memory so the
operator can delay printing until a later time if desired.
1.2 Otoacoustic Emissions
What Are DPOAEs?
Distortion Product Otoacoustic Emissions (DPOAEs) are acoustic signals that can be detected in the ear
canal of a person with normal outer hair cell function, subsequent to stimulation of the auditory system
with a pair of pure tones at frequencies f
1
and f
2
. The resulting emission of interest is the distortion
product tone at the frequency 2f
1
-f
2
.
What Are TEOAEs?
Transient Evoked Otoacoustic Emissions (TEOAEs) are
acoustic signals that can be detected in the ear canal
of a person with normal outer hair cell function,
subsequent to stimulation of the auditory system with
a series of wideband clicks.
What Do Otoacoustic Emissions Results Tell Us?
Available evidence suggests that otoacoustic
emis
sions (OAEs) are generated by the cochlea’s outer
hair cells, and that the presence of OAEs is an
indication that the outer hair cells are normal.
Although OAE test data provide no indication of inner
hair cell function, or of hearing ability, current
research indicates that the majority of hearing-impaired individuals can be identified by a simple OAE
test. Patients who fail to generate OAEs should be rescreened and/or referred for additional audiological
testing.
6
How Does the
ERO•SCAN
Pro Device Measure DPOAEs?
The
ERO•SCAN
Pro instrument generates a series of test tones, directs them into the ear canal, and
then measures the level of the DPOAE tone generated by the cochlea. By using different test
frequencies, the
ERO•SCAN
Pro device provides an estimate of outer hair cell function over a wide
range of frequencies.
How Does the
ERO•SCAN
Pro Device Measure TEOAEs?
The
ERO•SCAN
Pro instrument generates a series of clicks, directs them into the ear canal, and then
analyzes the spectrum of the returning signal, separating the noise and emission. By using bandpass
filters, the
ERO•SCAN
Pro device provides an estimate of outer hair cell function over a wide range of
frequencies.
7
How Does the
ERO•SCAN
Pro Device Work?
The digital signal processor in the instrument generates two pure tones (f
1
and f
2
) for DPOAEs or a
series of wideband clicks for TEOAEs through a digital-to-analog converter. These tones or clicks are
presented to the ear via speaker tubes located in the probe. A microphone in the probe measures the
sound in the ear canal and transmits the signal to the analog-to-digital converter. The digital signal
processor then uses Fast-Fourier Transforms (FFTs) to filter the signal into narrow frequency bands, and
detects any emissions present. The level of these emissions can be compared with the level of the noise.
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