Appendix A: Test Sequence - Interacoustics OtoRead Operation Manual

Appendix A: Test Sequence

A complete test sequence consists of an auto start, calibration and
test phase. The auto start phase determines when the calibration
phase should proceed, while the calibration phase calibrates the
level of the tones that will be applied during the actual test phase.
Artifact rejection is employed during the test phase to reduce the
effect of transient noise bursts. Immediately after the test button is
pressed, the auto start phase of the test begins. Auto start checks
both the quality and stability of the seal by measuring the response
obtained from a sequence of test tones.
The stability of the seal is determined by comparing the responses
obtained over time. When the level of the response is within an
acceptable range and is stable over time, the unit proceeds to the
calibration phase.
FOR DPOAE:
The calibration phase automatically measures the response
obtained from a sequence of calibration tones and calculates
the voltage needed to obtain the desired pressures. If one or
more of the desired pressures cannot be obtained, the
instrument terminates operation and displays an error
message. A successful calibration leads to the actual test
phase.
The test phase consists of measuring the response obtained
from the pairs of test frequencies (f1, f2) applied to the
receivers. Two receivers are used, with each receiver
generating one frequency in order to reduce intermodulation
distortion. Frequency domain estimates of the actual P1, P2,
distortion (DP) and noise floor (NF) are obtained via the
discrete Fourier Transform, with a bin resolution of
approximately 31 Hz. The NF estimate is obtained by
averaging the power in the 4 closest (+/-2) bins to the DP bin.
FOR TEOAE:
The calibration phase automatically measures the peak
pressure obtained from a sequence of clicks and calculates
the voltage required to obtain the target peak pressure. If the
OtoRead Screener Appendix A: Test Sequence Page 49