Coded waveforms for optimised air-coupled ultrasonic nondestructive evaluation

David Hutchins; Pietro Burrascano; Lee Davis; Stefano Laureti; Marco Ricci

doi:10.1016/j.ultras.2014.03.007

Coded waveforms for optimised air-coupled ultrasonic nondestructive evaluation

Ultrasonics. 2014 Sep;54(7):1745-59. doi: 10.1016/j.ultras.2014.03.007. Epub 2014 Mar 24.

Authors

David Hutchins¹, Pietro Burrascano², Lee Davis³, Stefano Laureti⁴, Marco Ricci²

Affiliations

¹ School of Engineering, University of Warwick, Coventry CV4 7AL, UK. Electronic address: D.A.Hutchins@warwick.ac.uk.
² Polo Scientifico Didattico di Terni, Università degli Studi di Perugia, 05100 Terni, Italy.
³ School of Engineering, University of Warwick, Coventry CV4 7AL, UK.
⁴ School of Engineering, University of Warwick, Coventry CV4 7AL, UK; Polo Scientifico Didattico di Terni, Università degli Studi di Perugia, 05100 Terni, Italy.

PMID: 24726137
DOI: 10.1016/j.ultras.2014.03.007

Abstract

This paper investigates various types of coded waveforms that could be used for air-coupled ultrasound, using a pulse compression approach to signal processing. These are needed because of the low signal-to-noise ratios that are found in many air-coupled ultrasonic nondestructive evaluation measurements, due to the large acoustic mismatch between air and many solid materials. The various waveforms, including both swept-frequency signals and those with binary modulation, are described, and their performance in the presence of noise is compared. It is shown that the optimum choice of modulation signal depends on the bandwidth available and the type of measurement being made.

Keywords: Air-coupled; Coded waveforms; Cross-correlation; Non-destructive evaluation; Ultrasonic.