Real-Ear Measurements 137
To test directionality:
1. Place the probe tube in your client’s ear as described in Section 5.2.4, and
level the sound field speaker as described in Section 5.2.6. Although we
recommend a 45º azimuth for real-ear measurements, for this measurement
you should use a 0º azimuth, with the sound field speaker directly in front
of the patient.
2. Place the hearing aid in your client’s ear, making sure not to move the probe
tube.
3. Enter the Unaided & Aided Response screen. Use the [NEXT] and [BACK]
keys if necessary.
4. Press [MENU] to enter the real-ear menu. Make sure that CUSTOM is select-
ed for UNAIDED. Use the arrow keys to make the selection, if necessary.
Press [EXIT] to return to the real-ear measurement screen.
5. Press [F1] to clear all existing curves, if necessary.
6. Use [F2] to select AIDED #1.
7. Use [F4] to select the signal type. Use NORM, COMP, or DIG SPCH.
8. Use [
∨, ∧] to select a signal source of 65 dB SPL.
9. Press [START/STOP] to take the measurement. If you’re using a COMP or
DIG SPCH signal, press [START/STOP] again to stop the signal once the
measurement has stabilized. This curve will be the “forward” measurement.
10. Turn your client around so that the back of his head is facing the speaker.
See Figure 5.4.4A. Alternately, if you are using an external speaker on a
swing arm, you can swing the speaker around the client.
11. Use [F2] to select CUSTOM UNAIDED. Although this is an aided measure-
ment, the “unaided” measurement slot will give you a nice directional sub-
traction curve when the second measurement is completed.
12. Use [F4] to select the signal type used in the “forward” measurement.
13. Use [
∨, ∧] to select a signal source of 65 dB SPL.
14. Press [START/STOP] to take the measurement. If you’re using a COMP or
DIG SPCH signal, press [START/STOP] again to stop the signal once the
measurement has stabilized. This curve is the “reverse” measurement. See
Figure 5.4.4B.
15. Press [NEXT] to enter the Insertion Gain screen. The displayed measurement
curve is the difference between the “forward” and the “reverse” measure-
ments, or the amplification advantage provided by the directional micro-
phones of the hearing aid. See Figure 5.4.4C.
