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Open AccessArticle

MEMS Microphone Array Sensor for Air-Coupled Impact-Echo

Technische Universität München (TUM), Chair of Non-destructive Testing, Baumbachstr. 7, 81245 Munich, Germany
Author to whom correspondence should be addressed.
Academic Editor: Thomas Schumacher
Sensors 2015, 15(7), 14932-14945;
Received: 30 April 2015 / Revised: 8 June 2015 / Accepted: 18 June 2015 / Published: 25 June 2015
Impact-Echo (IE) is a nondestructive testing technique for plate like concrete structures. We propose a new sensor concept for air-coupled IE measurements. By using an array of MEMS (micro-electro-mechanical system) microphones, instead of a single receiver, several operational advantages compared to conventional sensing strategies in IE are achieved. The MEMS microphone array sensor is cost effective, less sensitive to undesired effects like acoustic noise and has an optimized sensitivity for signals that need to be extracted for IE data interpretation. The proposed sensing strategy is justified with findings from numerical simulations, showing that the IE resonance in plate like structures causes coherent surface displacements on the specimen under test in an area around the impact location. Therefore, by placing several MEMS microphones on a sensor array board, the IE resonance is easier to be identified in the recorded spectra than with single point microphones or contact type transducers. A comparative measurement between the array sensor, a conventional accelerometer and a measurement microphone clearly shows the suitability of MEMS type microphones and the advantages of using these microphones in an array arrangement for IE. The MEMS microphone array will make air-coupled IE measurements faster and more reliable. View Full-Text
Keywords: nondestructive testing of concrete; Impact-Echo; air coupled sensing; array techniques; MEMS microphones nondestructive testing of concrete; Impact-Echo; air coupled sensing; array techniques; MEMS microphones
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Groschup, R.; Grosse, C.U. MEMS Microphone Array Sensor for Air-Coupled Impact-Echo. Sensors 2015, 15, 14932-14945.

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