Abstract: The acoustic powers of noises radiated by various components are estimated with a function of square of vibration velocity to time and their averages at vibration surfaces of engine components that radiate noises. The main sources of surface noises of a four-cylinder diesel engine used in a vehicle are identified. Then the main sources of surface noises are found out by sound intensity testing technique, too. The study results of surface vibration testing are verified by sound intensity testing with good agreement. Improvement direction of diesel noise control is put forward based on the previous study.

Key words: Diesel, Sound intensity method, Source of noise, Surface vibration