Frye FONIX FP40D - Manual (Page 56)

48 FONIX FP40 Portable Hearing Aid Analyzer
3.5.1 Testing with Digital Speech
To test digital aids with noise suppression, we have taken our standard continuous Composite signal
and interrupted it at intervals just long enough to trick the hearing aid into thinking it is hearing
speech instead of noise. This program is called “Digital Speech” and comes equipped with two dif-
ferent speech spectra: the ANSI S3.42 spectrum that is similar to the Composite signal spectrum,
and the ICRA spectrum that was used in the creation of some high end digital hearing aids.
The nice thing about Digital Speech on the FP40 is that it works the same way as any other type of
signal works. You don’t have to learn any new button pushes, and you can treat the digital aid just
as you would any other hearing aid. In fact, there’s no reason that you can’t use the Digital Speech
signal for testing an analog hearing aid.
To use digital speech:
Follow the instructions from Section 3.4.1 to choose a Digital Speech source (DIGSP ANSI or DIGSP
ICRA), and test the aid according to Section 3.4.2. You can present the signal to the aid as long as
you need to, without worrying about the aid going into its “noise suppression” mode.
To understand ICRA vs. ANSI:
There are two Digital Speech signals available: Digital Speech ICRA (DIGSP ICRA) and Digital
Speech ANSI (DIGSP ANSI). They have different speech weightings. DIGSP ANSI rolls off the high
frequencies of the broadband signal at the same rate as the Composite Signal. DIGSP ICRA rolls off
the high frequencies of the broadband signal more quickly. Figure 3.5.1 shows a comparison of the
two speech spectra.
Figure 3.5.1—Comparison of DIGSP ANSI (CRV 1) and DIGSP ICRA (CRV 2)
3.5.2 Testing with the Composite Signal
If you don’t have Digital Speech on your analyzer, you can still perform accurate measurements of
the hearing aid using the Composite signal. Most noise suppression features on high end digital aids
will accept a continuous signal for several seconds before decreasing the gain of the hearing aid.