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10 Real-Ear Measurement Setup
10.1 Section overview
For safe and effective operation, the Real-Ear Measurement (REM) system 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. Note that the REM
speaker is in the lid of the test chamber which must be open to a near-vertical
position for all real-ear measurements.
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 real-ear
SPL and the 2cc coupler SPL produced by the same transducer driven by the
same signal.
This section covers the following topics:
10.2: REM calibration facts
10.3: Calibration of REM probe microphone
10.4: Calibration check for probe module
10.5: Max TM SPL setup
FastFacts 10.1: Real-ear measurement setup
10.2 REM calibration facts
The probe microphone and its associated tubing does not have a flat frequency
response. The REM calibration process compares this response with the flat,
factory-calibrated response of the REM 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 1 am the following day or at 1 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 REM microphones.
It is suggested that a copy of the calibration curves for the probe modules when
new be posted near the RM500SL for comparison with daily or weekly curves. If
there is a drift in calibration with time, the module may need replacement. See
10.4: Calibration check for probe
Calibration should be repeated if probe modules are switched or if a probe-tube
with different dimensions is installed.
FastFacts 10.2: REM calibration facts
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module.
RM500SL User's Guide Version 2.8
10.6: ABR nHL to eHL setup
10.7: Positioning the client
10.8: Positioning the probe tube
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