Audioscan Axiom User Manual download pdf (Page 47)

Axiom

User's Guide Version 1.8



May 2015

9 ANSI Hearing Aid Tests

These tests follow the procedures of ANSI S3.22-1996 or ANSI S3.22-2003 as selected in Setup. See 1996 or

2003 ANSI standard :

Linear: An automated test sequence for linear hearing aids per ANSI S3.22.

AGC: An automated test sequence for AGC hearing aids per ANSI S3.22.

ANSI S3.22-1996 facts

The Axiom performs selected hearing instrument tests in accordance with ANSI S3.22-1996. This standard

expresses some outputs and gains as High Frequency Average (HFA) values. The HFA is the average of values

at 1000, 1600 and 2500 Hz. If a hearing aid meets certain conditions, the manufacturer may choose other

averaging frequencies called Special Purpose Average (SPA) frequencies. The current averaging frequencies are

indicated explicitly on test results where space permits and also appear as tick marks on the frequency axis of

graphs. To change the averaging frequencies, see ANSI test frequencies.

This standard also requires some tests with the gain control full on and some with the gain control in the

Reference Test Position (RTP). This requirement applies to both Linear and AGC aids that have a HFA (or SPA)

full-on gain greater than the HFA (or SPA) OSPL90 minus 77 dB. Otherwise the RTP is full on. If required, the

Axiom will pause in its testing and guide you in setting the gain control to the RTP.

All other controls on the hearing instrument should be set to provide the widest frequency response, the greatest

gain and the highest maximum output. AGC controls and/or programmable parameters should be set as

designated by the manufacturer.

At full-on gain the [Linear] and [AGC] test sequences provide a curve of OSPL90 (Output Sound Pressure Level

for a 90 dB input SPL), the HFA (or SPA) and peak value of this curve, the frequency of the peak and the HFA

(or SPA) gain for a 50 dB input SPL.

With the gain control at RTP, these sequences also provide a frequency response curve with an input SPL of 60

dB (Linear) or 50 dB (AGC), the HFA (or SPA) gain for a 60 dB input SPL, the frequency range, battery drain,

equivalent input noise, harmonic distortion, attack and release time (AGC only).

ANSI S3.22-2003 facts

ANSI S3.22-2003 has been designated a recognized standard by the FDA and is mandatory for reporting test

data.

The most significant change from the 1996 version is the requirement for the hearing aid to be set in its most

linear mode for the setting of the gain control to Reference Test Setting (changed from Reference Test Position)

and for all tests except attack and release and input-output (I/O) curves. These two tests are to be conducted with

the AGC function set for maximum effect. The AGC test sequence will pause to allow AGC to be set prior to

measuring attack and release time.

Full-on gain is determined with 50 dB input SPL (60 dB was formerly an option) and frequency response curves

are run at 60 dB SPL for Linear and AGC aids.

The OSPL90 curve, the HFA (or SPA) and peak value of this curve, the frequency of the peak, the HFA (or

SPA) full-on gain are determined at full-on gain setting. The response curve, frequency range, Reference Test

Gain, battery drain, equivalent input noise, distortion, attack and release times are determined at RTS.

These changes result in more consistent values for reference test gain, equivalent input noise and attack and

release time. See 1996 or 2003 ANSI standard, 8.2: ANSI S3.22-1996 facts and 8.5: ANSI 2003 Linear and

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