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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.


Photograph of the printed circuit board with 35 single MEMS microphones and additional circuitry.
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sensors-15-14932-f008: Photograph of the printed circuit board with 35 single MEMS microphones and additional circuitry.

Mentions: MEMS microphones need additional circuitry for power supply and signal conditioning. These features should not increase the noise level of the single microphones. We employed ultralow noise operational amplifiers to sum up the signals of the individual microphones and to bring the output signal to a level that can be easily measured with a digital oscilloscope or any other conventional recording system. A printed circuit board (PCB) carrying the individual MEMS microphones and the additional circuitry (power supply and preamplifier) was designed. Material on the PCB not needed for supporting individual parts or conducting paths has been removed in order to not influence the sound propagation and to minimize the effects of the supporting structure to the frequency response (Figure 8). In this way, flexibility concerning the use of different back baffling materials or stacking several of these sensor arrays can be maintained.


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

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

Photograph of the printed circuit board with 35 single MEMS microphones and additional circuitry.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-14932-f008: Photograph of the printed circuit board with 35 single MEMS microphones and additional circuitry.
Mentions: MEMS microphones need additional circuitry for power supply and signal conditioning. These features should not increase the noise level of the single microphones. We employed ultralow noise operational amplifiers to sum up the signals of the individual microphones and to bring the output signal to a level that can be easily measured with a digital oscilloscope or any other conventional recording system. A printed circuit board (PCB) carrying the individual MEMS microphones and the additional circuitry (power supply and preamplifier) was designed. Material on the PCB not needed for supporting individual parts or conducting paths has been removed in order to not influence the sound propagation and to minimize the effects of the supporting structure to the frequency response (Figure 8). In this way, flexibility concerning the use of different back baffling materials or stacking several of these sensor arrays can be maintained.

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.