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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) Directional sensitivity pattern for a microphone array consisting of 35 single microphones, spatial arrangement shown in (b).
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sensors-15-14932-f006: (a) Directional sensitivity pattern for a microphone array consisting of 35 single microphones, spatial arrangement shown in (b).

Mentions: The employment of several microphones as a single sensing element can be understood as an optimization of the directivity pattern of the combined sensing element. When defining the actual arrangement of microphones in an array, one has to consider the frequency dependence of the directional sensitivity (also termed polar pattern). To suppress side lobes, uniform distances between single microphones have to be avoided [22,23]. Due to the customizable and steerable directivity such array arrangements are commonly used in the field of technical acoustics for source localization tasks [23]. We adopted such a design to fit to the requirements for IE testing of typical plate structures. Figure 6 shows the polar pattern of the proposed microphone array arrangement consisting of 35 single microphones.


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

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

(a) Directional sensitivity pattern for a microphone array consisting of 35 single microphones, spatial arrangement shown in (b).
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-14932-f006: (a) Directional sensitivity pattern for a microphone array consisting of 35 single microphones, spatial arrangement shown in (b).
Mentions: The employment of several microphones as a single sensing element can be understood as an optimization of the directivity pattern of the combined sensing element. When defining the actual arrangement of microphones in an array, one has to consider the frequency dependence of the directional sensitivity (also termed polar pattern). To suppress side lobes, uniform distances between single microphones have to be avoided [22,23]. Due to the customizable and steerable directivity such array arrangements are commonly used in the field of technical acoustics for source localization tasks [23]. We adopted such a design to fit to the requirements for IE testing of typical plate structures. Figure 6 shows the polar pattern of the proposed microphone array arrangement consisting of 35 single microphones.

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.