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Chapter 3
Conformance Testing
3.1 Introduction
This chapter contains the information needed to conduct conformance testing according to the specified
standards.
3.2 Selecting C-weighting
Normally, Sound Level Meter Type 2240 measures L
AF
, L
AFmax
, L
Aeq
and L
Cpeak
, but for testing
purposes it is possible to replace the A-weighting with C-weighting, so that L
CF
, L
CFmax
, L
Ceq
and
L
Cpeak
are measured.
To do this, press and hold the Sound Level Range key for more than 10 seconds – the display now
shows C-weighted parameters. Repeating this action returns the instrument to its normal mode.
3.3 Mounting for Acoustical Tests
For acoustical tests, it is important that the test rig for mounting the microphone to be tested is
designed to minimise the influence of reflections to a level that is comparatively smaller than the test
parameter's maximum Expanded Uncertainties of Measurement. This has to be demonstrated with a
good, known laboratory microphone.
During acoustic tests, the sound level meter must be placed in a reflection-free room. According to
good practice in acoustic laboratories, the sound level meter must be placed in a way that eliminates
any surrounding influence.
3.4 Mounting for Mechanical Vibrations Tests
Type 2240 should be mounted on the shaker with a suitable holder so that the vibration is applied in a
direction perpendicular to the plane of the microphone diaphragm.
3.5 Electrical Substitute for Microphones
To obtain a BNC type electrical input, replace the microphone with a WA-0302 – A 12 pF fitted with a
UA-0245 adaptor.
All electrical inputs can be short-circuited when needed for testing.
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