ISO 6798-2-2020 pdf download.Reciprocating internal combustion engines – Measurement of sound power level using sound pressure- Part 2: Survey method.
The engine noise radiated is affected by the supporting type of engine, connection type with dynamometer equipment and installation height, lithe mounung base Is rigid, the engine should be resiliently mounted on the base, lithe mounting base is resilient, the engine Is permitted rigidly mounted on the base The engine should be resiliently connected with dynaniometer equipment. The distance of the engine lowest noise radiation surface (usually is oil pan bottom) and the reflecting plane (the ground) should be less than or equal to 0.5 m.
6.3 EngIne conditions and operation conditions
6.3.1 EngIne condlUons
The engine noise radiated is affected by the auxiliaries which are equipped on the engine; the conditon of engine shall meet the requirements oF ISO 3046.1. Any air cleaner, exhaust silencer and cooling Ian, etc.. ii 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 Irons any such driven machinery shall hr regarded as extraneous noise.
NOTE I kit the determination of the sound power level 01 exhaust noise, see 1St) I 5619. For special purposes. the teat distance starts from the -ontour ot the e*hausl pipe and a miumber of measuring points of two (90 Ici outlet) cam he used although not recommended.
NOTE 2 kit the determination oft hr ciund iwer level of Intake minise, see 15011’S 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 nun’basbc auxiliaries shall be regarded as extraneous noise, or this equipment or nori’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 cii the extraneous noise, and by using a muffler to reduce the aerodynamic noise (gas/liquid).
6.3.2 Operating conditions
Fur the noise measurement, the engine shall b 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.
Mrasurementa can be made in accelrrntcd/decelrrated conditions and other operating conditions it 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 plaise This method can be used tar comparative tests.ISO 6798-2 pdf download.