title: The application of time-frequency analysis to the air-coupled ultrasonic testing of concrete.
abstract: Air-coupled ultrasound has been used for the nondestructive evaluation of concrete, using broad bandwidth electrostatic transducers and chirp excitation. This paper investigates the benefits of using time-frequency analysis in such situations, for both waveform retrieval and imaging in the presence of low signal levels. The use of the short-term Fourier transform, the Wavelet transform, and the Wigner-Ville distribution all are considered, in which accurate tracking of the ultrasonic chirp signals is demonstrated. The Hough transform then is applied as a filter. An image of a steel reinforcement bar in concrete has been produced to illustrate this approach.
authors.affiliation: School of Engineering, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: James R
authors.initials: JR
authors.lastname: Berriman
authors.forename: David A
authors.initials: DA
authors.lastname: Hutchins
authors.forename: Adrian
authors.initials: A
authors.lastname: Neild
authors.forename: Tat Hean
authors.initials: TH
authors.lastname: Gan
authors.forename: Phil
authors.initials: P
authors.lastname: Purnell