Chapter 3: Specification Test Procedure; Source Frequency Accuracy; Digital Measurement And Readout Of Spl Accuracy; Source Attenuator Accuracy - Frye FONIX 8000 Maintenance Manual

Chapter 3: Specification Test Procedure

3.1 Source Frequency Accuracy

Instrument required: Frequency counter accurate to 0.1 percent and capable of mea-
suring 1000 Hz.
Setup: Enter the Coupler screen. From the menu, set the static tone to single, and
the output transducer to Telewand. Exit the menu. Set the amplitude to 100 mA/M
and the frequency to 1000Hz. Connect the frequency counter to the sound chamber
Telewand connector.
Measurement: The frequency counter should read 1000Hz within 1% plus the toler-
ance of the counter.

3.2 Digital Measurement and Readout of SPL Accuracy

Instrument required: Precision sound level meter with 1/2 inch condenser micro-
phone. Response set to flat frequency response (C weighted).
Setup: Enter the coupler screen. From the menu, set noise reduction (tone) to "off"
and static tone to "single." Exit the menu. Set the 8000 amplitude to 90dB. Place
the sound level meter's microphone at the reference point in the sound chamber.
Place the 8000 coupler microphone so that its grill is facing the sound level meter's
microphone's grill and is 1/8" away from it. Leave the chamber lid open and make
sure the room is very quiet.
Measurement: Starting at 200Hz, measure the RMS levels at the reference point
with both systems for each puretone frequency. They should agree within 1 dB
(+/- 1 digit) from 300 to 5000 Hz and within 2 dB (+/- 1 digit) at all other frequen-
cies, plus the tolerance of the sound level meter.

3.3 Source Attenuator Accuracy

Instrument required: Precision A.C. voltmeter, such as the HP974A, that is accurate
at 1KHz, has dB relative and auto ranging features.
Setup: Enter the coupler screen. From the menu, set the static tone to "single",
and the output transducer to "telewand." Exit the menu. Set the 8000 to 1KHz and
100mA/M. Connect the voltmeter to the sound chamber telewand connector. Set the
meter to autoranging and dB relative modes.
Chapter 3: 9