Excitation and spectral calibration of acoustic emission systems

A method for calibrating a high frequency audio transducer comprising:

• a. acoustically coupling said transducer to a reference material and exciting said material with a broad spectrum noise means comprising a gas jet applied to a surface thereof, thereby generating an output signal from said transducer;
• b. amplifying and analysing said output signal;
• c. acoustically coupling a second transducer having a flat frequency response up to about 1 MHz to said reference material excited by said broad spectrum noise thereby generating a comparison output signal from said second transducer;
• d. amplifying and analysing said comparison output signal;
• and
• e. calibrating said output signal against said comparison output signal.

Apparatus for use in spectral calibration of acoustic emission systems comprising:

• a reference material;
• a test piece;
• broad spectrum noise means for excitation of said reference material and said test piece;
• transducer means for acoustic coupling to said test piece;
• a comparison transducer having a flat frequency response up to about 1 MHz for acoustic coupling to said reference material;
• and
• means for recording and analysing an output signal from said transducer means coupled to said test piece relative to an output signal from said comparison transducer coupled to said reference material to produce a calibrated output signal representative of an acoustic emission event in said test piece.