Noise controlling by means of intensity of acoustic radiation measurements

Abstract

Noise control in working places often involves the design of acoustic treatment of enclosures and the design of proper devices able to reduce vibration of surfaces in machinery and structural borne propagation. However, in order to optimize the efficiency of the treatment, it would be very useful to properly relate the vibration with total sound emission. From a general point of view, it is quite important to determine the relation between vibration surfaces and total sound (or noise) emission. The same problem could be also studied for several other sources, such as loudspeakers or musical instruments. We employ the Intensity of Acoustic Radiation (IAR), a novel, corresponding parameter introduced recently, that relates modal analysis with sound production. This parameter is defined as the space-averaged amplitude of cross-spectrum between sound pressure caused by the movement of the vibrating surface and the velocity of the vibration of the surface itself. To measure IAR, an omnidirectional microphone is placed in a fixed position at a short distance over the surface, while an accelerometer is mounted at the same points utilized during modal analysis. IAR showing a very high correlation between Frequency Response Function (FRF) and sound production of the surfaces is, therefore, able to describe the relationship between vibration and noise emission.