Experimental validation of force radiation modes: a novel approach to reduction of sound radiation from vibrating structure

摘要

The location of a vibration source within a machine is sometimes found to have a significant effect upon its radiated sound power. Radiation mode analysis is known to be a powerful tool for interpreting sound radiation since those modes are independent of a structure's surface vibration. However, knowledge of the radiation modes alone cannot be used directly to understand the relationship between vibration source location and acoustic power radiation. Previously, it was suggested that the radiation mode concept can be extended to understand the relationship between the acoustic power and the driving force distribution by combining a structure's mobility matrix and its radiation modes to form force radiation modes (f_(rad)-modes). It was demonstrated by simulation that the radiated sound power can be reduced by choosing the driving force location to be the nodes of the force radiation modes. To further validate the usefulness of the force radiation mode concept, the acoustic transfer vectors and the mobility matrix of a thin steel strip mounted in a rigid baffle were measured. The force radiation modes were calculated by using the experimental data and it was confirmed that the force radiation modes can serve as a practical guide for reducing the radiated sound power, especially at low frequencies.