Ngara
User Manual
7
Reference Specifications
7.1 Applicable Standards
• IEC 61672:2006 (Class 1)
• AS / NZS CISPR 22:2006 (Class A)
7.2 Acoustic Reference Conditions
Reference acoustic values are given in Table 28.
Table 28: Acoustic Reference
Description
Value
Level
94
dB
Frequency
1
kHz
Direction
Along centre axis of microphone/preamplifier
Linear Operating Range
25
to
120
dB
(
A
/
C
)
Acoustic Noise Floor
20
dB
(
A
)
typically
Electrical Noise Floor
20
dB
(
A
)
typically
Note that the
94dB
Sound Pressure Level is also to be used as the starting level for all linearity tests.
7.3 Environmental Reference Conditions
Reference environmental conditions are given in Table 29.
Table 29: Reference Environmental Conditions
Description
Value
Air Temperature
23°C
Static Pressure
101.325 kPa
Relative Humidity
50%
Settling Time
10 seconds
A minimum of 5 minutes should be provided for stabilisation after changes to environmental conditions
7.4 Adjustments to Indicated Levels
Calibration is performed using the Remote Host software (Section 5.6) or via the on-board push button interface
(Section 4.4.5).
Recommended calibration components –
• Acoustic Calibrator – NC-74
Using the above calibrator a reference tone at 94dB (A) is equal to 94.00dB (A) as seen by Ngara.
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