Acoustic Source Identification Research Articles

Acoustic emission source identification

Acoustic emission, the phenomenon of stress wave release from microstructural alterations in solid materials, has not optimally fulfilled its promise as a nondestructive testing technique since the precise characteristics of the stress waves emitted from specific sources remain unknown. The present work describes an experimental system which overcomes the numerous problems associated with conventional piezoelectric transducers and video tape recorders and permits the precise characteristics of the acoustic emission signal to be determined. This system incorporates a laser beam interferometric surface displacement detector and a high speed digital capture and signal processor. The present work also describes how proper choice of workpiece geometry coupled with analytical calculations yields new insight into the influence of workpiece transfer function on the detected acoustic emission signal. Finally, comments will be made as to the possibility of acoustic emission source identification in practical field situations. [Work supported by Naval Sea Systems Command.]

Directional acoustic measurements by laser Doppler velocimeters

Laser Doppler velocimeters (LDV’s) are used as velocity microphones to measure sound pressure level in the range of 90–130 dB, spectral components, and two-point correlation functions for acoustic noise source identification. Close agreement between LDV and microphone data is observed. Directional sensitivity and the ability to measure remotely make LDV’s useful tools for acoustic measurement where placement of any physical probe is difficult or undesirable, as in the diagnosis of jet noise.