Frye FONIX 7000 - Manual (Page 125)

Automated Test Sequences
117
5.2 ANSI S3.42-1992 (ANSI 92)
The ANSI Option includes a test sequence based on the ANSI S3.42-1992 stan-
dard. This standard has been developed to test non-linear hearing aids with a
broadband noise signal. The need for this standard stems from the importance
of evaluating the performance of these circuits in a more real-world environ-
ment. ANSI 92 gives you: noise saturation sound pressure level, noise gain, a
family of frequency responses, and a noise input/output curve.
5.2.1 Understanding ANSI 92
The original signal used in the 7000 test system is that of a speech weighted set
of pure tones starting at 200 Hz and ending at 8000 Hz, with a gradual high fre-
quency roll off of 6 dB per octave. The knee point of the roll off is placed at 900
Hz. The spectrum was developed from data supplied by the National Bureau of
Standards, and is the signal used for the testing of hearing aids submitted for
use in the Veterans Administration hearing aid program.
In 1992, the ANSI standards committee for hearing aid test standards published
S3.42-1992. This standard describes a noise signal that is very similar to the
one we use in the 7000 test system. There are some differences, mostly in the
low frequencies and in the way that the signal spectral shape is specified. The
committee wanted a system that could be built easily by anyone, and assumed
that a manufacturer who would develop equipment to make tests for this stan-
dard would use a white noise signal to produce the roll off above the 900 Hz
knee point.
In order to produce a signal that met with the provisions of the S3.42 standard,
Frye Electronics decided to slightly modify the Composite signal for use in this
ANSI 1992 test sequence. This modified signal is not used in the normal com-
posite operation of the 7000 test system.
Only the most critical operator will see any significant difference in the hearing
aid performance between the two signals. The ANSI S3.42 signal may result in
an increase in noise gain by about 1 dB.
5.2.2 Running ANSI 92.
1. Level the sound chamber, and set up the hearing aid to full on gain as spec-
ified in Section 5.1.1 and 5.1.2.
2. Press [F4] in the Opening screen to enter the ANSI 92 screen.
3. Use [F1] to select the desired ear.
4. Use [F2] to select the settle time used for the test.
5. Use [F3] to set the noise reduction used for the test. See Section 2.3.2.1 for
more information on composite noise reduction.
6. Press [START] to begin the test sequence.