Reference Specifications; Applicable Standards; Acoustic Reference Conditions; Environmental Reference Conditions - Acoustic Research 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.
Description
Level
Frequency
Direction
Linear Operating Range
Acoustic Noise Floor
Electrical Noise Floor
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.
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.
Version — 25-7cd7566
Table 28: Acoustic Reference
Value
94dB
1kHz
Along centre axis of microphone/preamplifier
25 to 120dB(A/C)
20dB(A) typically
20dB(A) typically
Table 29: Reference Environmental Conditions
Description
Air Temperature
Static Pressure
Relative Humidity
Settling Time
Value
23°C
101.325 kPa
50%
10 seconds
Ngara
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