BS ISO 6798-2:2020 pdf free.Reciprocating internal combustion engines — Measurement of sound power level using sound pressure.
6.3 Engine conditions and operation conditions
6.3.1 Engine conditions
The engine noise radiated is affected by the auxiliaries which are equipped on the engine; the condition of engine shall meet the requirements of ISO 3046-1. Any air cleaner, exhaust silencer and cooling fan, etc., if equipped, shall be recorded in the report. A gearbox or any driven machinery which load the engine under test should be stated in the report. Noise radiated from any such driven machinery shall be regarded as extraneous noise.
NOTE 1 For the determination of the sound power level of exhaust noise, see ISO 15619. For special purposes, the test distance starts from the contour of the exhaust pipe and a number of measuring points of two (90° to outlet) can he used although not recommended.
NOTE 2 For the determination of the sound power level of intake noise, see ISO/TS 19425.
If it is essential to use equipment or non-basic auxiliaries (such as a blower for cooling) to do bench test for some engines with specified purposes (such as motorcycles). Noise radiated from this equipment or non-basic auxiliaries shall be regarded as extraneous noise, or this equipment or non-basic auxiliaries shall be temporarily turned off to ensure that the engine can operate normally.
The extraneous noise is a part of background noise; appropriate steps shall be taken to reduce extraneous noise in order to comply with 42. This can be done by shielding or wrapping the structure surface with a heavy material that has low transmission capabilities in the frequency range of the extraneous noise, and by using a muffler to reduce the aerodynamic noise (gas/liquid).
6.3.2 Operating conditions
For the noise measurement, the engine shall he operated at the ISO standard power and corresponding rate as defined in ISO 3046-1 under the ISO standard reference conditions in a steady state. At that time, the temperature of the oil and coolant shall be stable, the ambient and intake air temperature shall not be higher than 45 °C.
Measurements can be made in accelerated/decelerated conditions and other operating conditions if necessary, all measurements made in such conditions shall be stated in the test report.
The engine power and corresponding rate shall be measured according to the requirements of
ISO 3046-3.
7 Measurement
7.1 General
The survey method (accuracy grade 3) is a method for determining the sound power level (A-weighted) of the noise source from sound pressure levels measured on a measurement surface enveloping the noise source over a reflecting plane. This method can be used for comparative tests.
NOTE If declaration is necessary, see ISO 4871.BS ISO 6798-2 pdf download.