The use of broadband acoustic transducers and pulse-compression techniques for air-coupled ultrasonic imaging

• Published in: Ultrasonics Vol. 39; no. 3; pp. 181 - 194
• Main Authors: Gan, T.H., Hutchins, D.A., Billson, D.R., Schindel, D.W.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-04-2001; Elsevier Science
• Subjects: Acoustic instruments, equipment, and techniques; Acoustical measurements and instrumentation; Acoustics; Air-coupled ultrasound; Capacitance transducer; Exact sciences and technology; Fundamental areas of phenomenology (including applications); General equipment and techniques; Image Processing, Computer-Assisted; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Physics; Signal processing; Signal Processing, Computer-Assisted; Transducers; Ultrasonics; Ultrasonics, quantum acoustics, and physical effects of sound; Air-coupled ultrasound; Signal processing; Capacitance transducer; Acoustic transducers; Ultrasound imaging; Capacitive transducer; Material defect; Fiber reinforced material; Measuring methods; Experimental study; Pulse compression; Thickness measurement; Wide band; Image transmission; Aeroacoustics
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/S0041-624X(00)00059-7

A pulse-compression technique has been applied to air-coupled testing of solid materials. Capacitance transducers were used to generate wide bandwidth swept-frequency (chirp) signals in air, which were then used to measure and image solid samples in through transmission. The results demonstrate that such signal processing techniques lead to an improvement in the signal to noise ratio and timing accuracy for air-coupled testing. Measurements of thickness and spectroscopic experiments are presented. Images of defects in a wide range of materials, including metals and carbon-fibre composites have also been obtained. This combination of capacitive transducers with pulse-compression techniques is shown to be a powerful tool for non-contact air-coupled ultrasonic measurements.