Audioscan Axiom - Manual (Page 56)

Axiom ® User's Guide Version 1.8  May 2015
12 On-Ear Measures - Setup
For accurate, repeatable measurements, the Axiom must be properly set up and calibrated, the client must be
properly positioned and the probe tube must be properly positioned in the ear canal. Some common terms:
Real-Ear Unaided Response (REUR): SPL, or band SPL, in the open (unaided) ear canal for a given stimulus.
Real-Ear Unaided Gain (REUG): Difference, in dB, between the REUR and the stimulus SPL, or stimulus band
SPL.
Real-Ear Aided Response (REAR): SPL, or band SPL, in the ear canal for a given stimulus, with a working
hearing aid in place.
Real-Ear Aided Gain (REAG): Difference, in dB, between the REAR and the stimulus SPL, or stimulus band
SPL.
Real-Ear Saturation Response (RESR): The REAR obtained using a narrow-band signal at a level high enough to
saturate the hearing aid (usually 85 - 90 dB SPL).
Real-Ear-to-Coupler Difference (RECD): Difference, in dB, between the SPL produced in the ear canal and the
SPL produced in a coupler by the same sound source.
On-ear calibration facts
The probe microphone and its associated tubing does not have a flat frequency response. The on-ear calibration
process compares this response with the flat, factory-calibrated response of the on-ear reference microphone and
compensates all subsequent probe-tube measurements for this difference. It may be performed as often as
desired but will be invalidated at 12 am the following day or at 12 am the following Monday, depending on the
choice of Daily or Weekly calibration interval. After the calibration has expired, you will be prompted to
calibrate whenever you attempt a test that uses the on-ear measurement microphones.
It is suggested that a copy of the calibration curves for the probe modules when new be posted near the Axiom
for comparison with daily or weekly curves. If there is a drift in calibration with time, the module may need
replacement. See Calibration check for probe module.
Calibration should be repeated if a probe module is replaced or if a probe-tube with different dimensions is
installed.
Switching left and right probe modules after calibration will result in the wrong calibration curve being applied.
Calibration of on-ear probe microphone
Ensure the probe microphone assembly to be calibrated is plugged into the appropriate jack. See Microphone
connection and On-ear calibration facts
1. Click on and then click on [Calibration] within the [On-ear] menu.
2. Press the enlarged end of a probe tube as far as it will go, into the recessed opening at the top of the probe
module.
3. Position the open end of the probe tube in front of the reference microphone inlet and press it between the
posts as shown.
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