This Quick Guide is intended to provide information at a beginner level to assist the reader in their understanding of Real Ear Measures (REM). It will also explain some of the common terminology used for REM and within the Affinity 2.0 and Callisto™ software.
Why perform Real Ear Measures?
Not all hearing losses can be resolved by the same method, there are often many differences in the type of
Hearing Devices they are prescribed, the patient’s unique ear canal acoustics and the method in which the
Hearing Device is passing sound into the ear. Real Ear Measures help to overcome these differences by allowing the Audiologist to objectively measure and verify the sound that is being delivered at the ear drum.
The benefits of this process can be applied in varying scenarios from initial hearing aid fitting to troubleshooting. As a consequence, performing this method can help to gain better satisfaction from your patient from their first fitting and less follow up appointments.
REM can only be performed for Hearing Devices which deliver sound via an Air-Conduction method and not for devices which deliver sound via Bone-Conduction or Electrophysiological stimulation.
REM can be performed via three methods, Real Ear Insertion Gain, Real Ear Aided Gain and Real Ear Aided Response. All three achieve the same objective in fitting the hearing aid for the patient and they are all equally as efficient as one another. It is just a preference of which method is used.
What is the basic process of REM?
REM mainly involves placing a fine probe microphone into the ear canal to measure the sound at the ear drum. These measures include the response of the ear canal acoustics and the hearing aid and can help the clinician to adjust the hearing device specifically to the patients’ ears.
The REM process usually involves the following steps once hearing assessment has been performed.
This process sets up the conditions to allow comparison between the external microphone and the internal probe microphone. Once placed in the ear canal this will show the effect of the ear canal and hearing device amplification.
The calibration can be checked in the upcoming REUG measure through running a measurement in the same configuration as the calibration. When this is done a flat trace with a gain value at 0dB should be shown, please see the example below.
Performing this measurement allows you to make a consideration of the ears natural amplification of sound; this ensures that you are not fitting your hearing aid to over-amplify in certain regions of the frequency response.
Real Ear Occluded Gain (REOG) – this measurement involves the placement of the hearing device on the ear but muted/off. It allows consideration of the attenuation caused by the ear-piece and its obstructing effect of external sounds. This trace is usually performed with the REUG in view so that they can be compared – the difference between these curves is the amount of attenuation that the ear- piece is providing.
Real Ear Aided Response (REAR) or Real Ear Aided Gain (REAG) – this is a measure which involves the enabled/on hearing device being positioned on the ear with the ear-piece inserted as per normal use and the probe microphone inserted. This allows measurement of the hearing device’s amplification effect within the patients’ ear and includes the effect of the patients ear acoustics. This measure can be run at varying intensities but it is recommended that it is run at speech level (65dB) to ensure that the device is analyzed for the intensity that it will normally be used for.
It is often during this measurement that adjustment to the Hearing Device Manufacturers software is performed to help match a prescription target.
Real Ear Insertion Gain (REIG) – this is a measure which is performed in the exact same configuration as the REAR and REAG above but requires the REUG to be performed in advance of it. It does this because it only displays the dB gain view of what the hearing aid is doing and removing the REUR acoustics from this display. Please see the example of this below.
Again, it is common to make adjustments in your Hearing Device Manufacturers software to alter the response towards the prescription target following this measure.
It is essential to perform REAR, REAG and REIG at normal speech level (65dB) and some prefer to measure and adjust for soft (50dB) and loud (80dB) intensities also.
When do I use Calibrate for Open Fit?
When performing REM the stimulus needs to be maintained at the point of the patients head to ensure an accurate measurement is made.
This can be difficult when making REM measurements with Open Fit Hearing Aids because there is a lot of sound which leaks out of the ear canal and on to the reference microphone. Therefore the method used to perform REMs needs to be changed.
The two methods used are as follows:
Active Reference Method – this involves the external reference microphone on the REM headset monitoring and altering the stimulus from the speaker during the measurement. This is the best method to apply when measuring with occluding ear-pieces as there is minimal sound leakage onto the reference microphone.
The Affinity2 and CallistoTM is performing REM by default under this method.
Substitution or Stored Equalization Method – this involves a quick measurement prior to performing your Real Ear Measures to store the distance of the headset from the speaker. This ensures that constant signal intensity is maintained to achieve the measurement level at the patients head. However, this requires your patient to be very still to ensure an accurate measurement.
This method of performing REM is activated following ‘Calibrate for Open Fit’. This can be added as part of your REM test battery.