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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) Single Micro-Electro-Mechanical Sensor (MEMS) microphone; (b) schematic diagram of MEMS microphone; (c) frequency response curve for the audio range; and (d) frequency response curve for ultrasound of the used MEMS microphone. Reproduced with permission from [25].
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sensors-15-14932-f007: (a) Single Micro-Electro-Mechanical Sensor (MEMS) microphone; (b) schematic diagram of MEMS microphone; (c) frequency response curve for the audio range; and (d) frequency response curve for ultrasound of the used MEMS microphone. Reproduced with permission from [25].

Mentions: Typical civil engineering structures, such as plates made of concrete ranging in thickness from several centimeters to around one meter, will show IE resonance frequencies of 2–20 kHz. Thus, microphones for conventional audio purposes are principally suited as IE sensors. When the output of several microphones has to be combined, the sensor characteristics like sensitivity or frequency and phase response should be as similar as possible among all single microphones. Due to the manufacturing process MEMS type microphones fulfill this requirement better than electret based microphone capsules. Ham and Popovics recently showed the suitability of MEMS type microphones for NDT of concrete [24]. For a prototype array, we chose a model of MEMS based microphones similar to the one in the mentioned study (manufacturer: Knowles, type: SPU0410LR5H-QB, Figure 7a,b) described in Table 1 [25]. According to its datasheet, the microphone has a flat frequency response up to 10 kHz and a pronounced resonance peak between 20 kHz and 30 kHz increasing the sensitivity by approximately 11 dB. However, this behavior is no restriction for practical measurements since in the conventional interpretation scheme of IE data only the identification of the positions of frequency peaks is relevant and not the absolute quantification of pressure changes caused by surface displacements.


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

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

(a) Single Micro-Electro-Mechanical Sensor (MEMS) microphone; (b) schematic diagram of MEMS microphone; (c) frequency response curve for the audio range; and (d) frequency response curve for ultrasound of the used MEMS microphone. Reproduced with permission from [25].
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-14932-f007: (a) Single Micro-Electro-Mechanical Sensor (MEMS) microphone; (b) schematic diagram of MEMS microphone; (c) frequency response curve for the audio range; and (d) frequency response curve for ultrasound of the used MEMS microphone. Reproduced with permission from [25].
Mentions: Typical civil engineering structures, such as plates made of concrete ranging in thickness from several centimeters to around one meter, will show IE resonance frequencies of 2–20 kHz. Thus, microphones for conventional audio purposes are principally suited as IE sensors. When the output of several microphones has to be combined, the sensor characteristics like sensitivity or frequency and phase response should be as similar as possible among all single microphones. Due to the manufacturing process MEMS type microphones fulfill this requirement better than electret based microphone capsules. Ham and Popovics recently showed the suitability of MEMS type microphones for NDT of concrete [24]. For a prototype array, we chose a model of MEMS based microphones similar to the one in the mentioned study (manufacturer: Knowles, type: SPU0410LR5H-QB, Figure 7a,b) described in Table 1 [25]. According to its datasheet, the microphone has a flat frequency response up to 10 kHz and a pronounced resonance peak between 20 kHz and 30 kHz increasing the sensitivity by approximately 11 dB. However, this behavior is no restriction for practical measurements since in the conventional interpretation scheme of IE data only the identification of the positions of frequency peaks is relevant and not the absolute quantification of pressure changes caused by surface displacements.

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.