FONIX® 8000 - Frye Electronics

Real-Ear Measurements 183
Figure 8.5.4—Testing noise suppression of a digital hearing aid. REAR 2 was tested using
Digital Speech. REAR 3 was tested using the Composite Signal.
8.6 Directional Hearing Aids
A hearing aid directional response pattern can be directly measured with the
8120 sound chamber, using the coupler directional test screen. The anechoic
environment of this small chamber, coupled with a mechanical rotator system,
can inform the operator exactly where the optimal gain and the attenuation
angles occur.
The real ear test system, using the insertion gain screen, can give additional
information on the aid’s directional pattern while it is worn by the actual
patient. It should be realized that the ear and head structure by itself has directional
characteristics, sometimes called the head shadow effect. An aid which
is considered omnidirectional can display directional characteristics because of
this effect. A good directional aid should show very strong directional characteristics
when using the real ear insertion gain approach described in this section.
8.6.1 Using the insertion gain technique
The Real-ear Insertion Gain screen is ideal for performing real-ear measurements
of hearing aid directionality.
To test directionality:
1. Set up the patient for real-ear measurements by inserting the probe microphone
and hearing aid.
2. Place the sound field speaker behind the patient at 180° or 135° azimuth.
Point the reference microphone of the probe microphone set towards the
sound field speaker.
3. Enter the Real-ear Insertion Gain screen.
4. Press [LEVEL] to level the sound field speaker.