Measurement Of Oaes - Interacoustics OtoRead Operation Manual

How Does the OtoRead Device Measure DPOAEs?
The OtoRead 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 OtoRead device provides an estimate of
outer hair cell function over a wide range of frequencies.
How Does the OtoRead Device Measure TEOAEs?
The OtoRead 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
band pass filters, the OtoRead device provides an estimate of
outer hair cell function over a wide range of frequencies.
How Does the OtoRead Device Work?
The digital signal processor in the instrument generates two
pure tones (f1 and f2) 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. The SPL and frequencies of the test tones and the
averaging time used to process the signals can be determined
by the tester through adjustable settings maintained in static
memory within the OtoRead instrument.
What Frequency Range of Hearing is Estimated?
DPOAEs: Approximately 1 kHz to 12 kHz (depending on the
frequency range selected). Since the health of the hair cells in
the region of the f2 test frequency are estimated, and a) the
2f1-f2 emission frequency is at about six-tenths of the f2
frequency, b) emissions tend to be weak below 600 Hz or so,
and c) the ambient noise tends to be highest at low
frequencies, the lowest f2 test frequency that can be routinely
measured is about 1 kHz. TEOAEs: Roughly 500 Hz to 4 kHz.
OtoRead Screener

Measurement of OAEs

Introduction Page 10