Improvement of Sound Absorption Material for Diesel Engine Cover

In this work the acoustic treatment of an engine cover was designed based on airflow resistance and sound absorption data. Single layer and multilayer treatments with measured airflow resistance were employed to reduce noise radiated by a diesel engine. The analysis was focused in the region in which the “knocking” noise is particularly noticeable. The methodology of acoustic design was confirmed by in-vehicle noise measurements. The application of a sound absorption treatment with a controlled specific airflow resistance provided the highest noise attenuation. An improvement in the sound quality was also achieved due to a reduction in the “knocking” noise.