Company:VTT Technical Research Centre of Finland Products:Actran Acoustics Industries:Machinery | Overview: A night time noise complaint was issued from the residential area near one of Wärtsilä’s main large 4-stroke medium speed engine factories located in downtown Vaasa. This factory produces the Wärtsilä 32 ship engine which provides higher unit power, enhanced fuel consumption, significantly reduced componentry and integral computer control to a fiercely competitive sector of the engine business. The Wärtsilä facility produces about 500 engines per year and every engine is subjected to a test run. An investigation found that the likely source of the intolerable noise was from the exhaust from a W6L32E engine 1000 hour endurance test which was running continuously at 750 rpm and full load. Challenge: An environmental noise study was conducted
in the middle of the night when the test engine
was running, with measurements taken at
three locations between the test facility and
the nearby residential area. Sound pressure
level measurements indicated a peak in the
sound spectrum at the 100 Hz 1/3 octave
band at approximately 94 Hz in narrowband,
which corresponds to the crankshaft rotation
frequency (CRF) order of 7.5. Typically the
exhaust noise of the W6L32E engine should
have the highest peaks at CRF orders 3 and
4.5. The measured noise was found to be
well under the nighttime environmental noise
limit. The annoyance levels were presumed
to be high because of the dominant half order
modulated low frequency noise components.Benefits:
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