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Noise and Vibration -
Natural Frequency Test

Tel: (+44) 01926 863563
marine engine

Case Studies - noise and vibration

Power station noise design

Natural frequency test

Starter motor natural frequency test

The brief

A marine engine OEM had designed and built a starter motor assembly for one of its engines. FEA predicted a frequency of 36 Hz, but the assembly was complicated and there were several hoses and cables that would add damping. It was important to confirm the frequency, to ensure the starter motor assembly would not be excited by the engine frequencies, possibly leading to a fatigue failure. Our noise and vibration consultants were asked to do a natural frequency test.

accelerometer  measurements

natural frequency  measurements

Work done

Our noise and vibration consultants used an accelerometer with a sound level meter to measure the response of the assembly. Excitation came from a gentle blow from a mallet, which is standard for this sort of test. Our consultants recorded results on the sound level meter and averaged to give a crisp response graph. In this case, the frequency was 33 Hz pretty close to the FEA prediction but spread over quite a wide bandwidth by the damping from the hoses and cables.

finite element analysis