Brüel & Kjær 3638 Manuel De L'utilisateur page 40

36 Exhaust Noise Inspector Type 3638 – User Manual
Test Requirements
When preparing for a stationary vehicle sound level test, you must follow the regulatory re-
quirements for testing that are enforced in your area. This includes having answers to the
following questions:
1) Microphone position:
a) What should the distance be between the test vehicle and microphone?
b) Where should the microphone be placed in relation to the exhaust system outlet?
c) How far off the ground should the microphone be?
d) In which direction should the microphone be pointing?
e) Are there any exceptions, or special conditions?
2) Test operator:
a) May others, beside the test operator, be present during testing?
b) Where should the test operator (and others, if applicable) be during testing?
c) Where should these individuals not be standing?
3) Test environment:
a) Are there any obstacles such as a curbstone, other vehicles, car part, equipment,
bushes, etc., which may be overlooked. Most obstacles block, absorb or reflect
sound and are generally not allowed.
b) If there are surrounding objects, how close to the test vehicle and microphone may
they be?
c) What type of ground surface is required for testing?
d) What type of weather conditions is required for testing (outdoors)?
4) Background noise:
a) What background conditions are allowed?
b) How often must these conditions be tested?
c) How often must these conditions be reported?
d) What happens if the conditions change?
e) Are there any allowable methods that compensate for background noise?
5) Vehicle RPM:
a) At what engine speed (RPM) should a vehicle run?
b) Does the RPM requirement differ from vehicle to vehicle? Do motorcycles, personal
cars and transport lorries have specific RPM requirements?
c) What is the maximum power of the vehicle to calculate the correct RPM test value?
d) How should the RPM be determined?