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MEMS Microphone Array Sensor for Air-Coupled Impact-Echo.

Groschup R, Grosse CU - Sensors (Basel) (2015)

Bottom Line: 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 MEMS microphone array will make air-coupled IE measurements faster and more reliable.

View Article: PubMed Central - PubMed

Affiliation: Technische Universität München (TUM), Chair of Non-destructive Testing, Baumbachstr. 7, 81245 Munich, Germany. robin.groschup@tum.de.

ABSTRACT
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.

No MeSH data available.


(a) Phase spectra of displacement recordings on the surface of the simulated concrete plate. The arrows indicate the frequency of the IE resonance; (b) Graph display of phases of displacement recordings at the IE resonance.
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sensors-15-14932-f003: (a) Phase spectra of displacement recordings on the surface of the simulated concrete plate. The arrows indicate the frequency of the IE resonance; (b) Graph display of phases of displacement recordings at the IE resonance.

Mentions: For the presentation of simulation results we put emphasis on the surface displacements in a region around the impact position. Figure 3 shows the phase behavior of displacements measured by receivers placed on a line on the concrete surface. Most of the wave energy shows continuous phase shifts along the offset axis. This is due to the propagation of different wave modes along the sensor line. Only at the frequency of the ZGV-S1 Lamb mode—the so-called IE resonance frequency—wave phases remain constant over a considerable length (see arrows in Figure 3). In our simulation example, this frequency lies at 8 kHz and thus coincides well with the value predicted by the formula mentioned in Section 1 (for the chosen elastic parameters the concrete has a P-wave velocity of 4170 m/s).


MEMS Microphone Array Sensor for Air-Coupled Impact-Echo.

Groschup R, Grosse CU - Sensors (Basel) (2015)

(a) Phase spectra of displacement recordings on the surface of the simulated concrete plate. The arrows indicate the frequency of the IE resonance; (b) Graph display of phases of displacement recordings at the IE resonance.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541815&req=5

sensors-15-14932-f003: (a) Phase spectra of displacement recordings on the surface of the simulated concrete plate. The arrows indicate the frequency of the IE resonance; (b) Graph display of phases of displacement recordings at the IE resonance.
Mentions: For the presentation of simulation results we put emphasis on the surface displacements in a region around the impact position. Figure 3 shows the phase behavior of displacements measured by receivers placed on a line on the concrete surface. Most of the wave energy shows continuous phase shifts along the offset axis. This is due to the propagation of different wave modes along the sensor line. Only at the frequency of the ZGV-S1 Lamb mode—the so-called IE resonance frequency—wave phases remain constant over a considerable length (see arrows in Figure 3). In our simulation example, this frequency lies at 8 kHz and thus coincides well with the value predicted by the formula mentioned in Section 1 (for the chosen elastic parameters the concrete has a P-wave velocity of 4170 m/s).

Bottom Line: 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 MEMS microphone array will make air-coupled IE measurements faster and more reliable.

View Article: PubMed Central - PubMed

Affiliation: Technische Universität München (TUM), Chair of Non-destructive Testing, Baumbachstr. 7, 81245 Munich, Germany. robin.groschup@tum.de.

ABSTRACT
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.

No MeSH data available.