Limits...
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.


Setup for the numerical model.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4541815&req=5

sensors-15-14932-f002: Setup for the numerical model.

Mentions: Our goal is the design of an acoustic sensor with optimum sensitivity to the air coupled ZGV-S1 mode. So we are going to examine in detail the pressure changes in the air that arise from the surface movement of the concrete element caused by the ZGV-S1 Lamb wave. This wave is visible in the air as plane wave fronts. This fact implies that the wave arrives in phase along a certain aperture surrounding the impact position. To further investigate the behavior of this peculiar waveform, we rely on a more realistic simulation. We adopt a simulation approach proposed by Castaings et al. [19] and applied to IE by Baggens and Ryden [20]. The propagation of stress waves and the radiation of acoustic waves are studied by a finite element simulation in the frequency domain. The model consists of a plate of concrete (thickness 0.25 m) with an adjacent layer of air at the topside (Figure 2). The modeling was performed with a cylindrical symmetry (impact position in the center of symmetry) and a low reflecting boundary at the outer edges of the model. A free boundary was set at the lower surface of the model. A Gaussian monopuls with center frequency 15 kHz was used as the excitation source. Typical values were chosen for the elastic properties of concrete (Young’s modulus 36 GPa, density 2300 kg/m3, Poisson’s ratio 0.2).


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

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

Setup for the numerical model.
© Copyright Policy
Related In: Results  -  Collection

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

sensors-15-14932-f002: Setup for the numerical model.
Mentions: Our goal is the design of an acoustic sensor with optimum sensitivity to the air coupled ZGV-S1 mode. So we are going to examine in detail the pressure changes in the air that arise from the surface movement of the concrete element caused by the ZGV-S1 Lamb wave. This wave is visible in the air as plane wave fronts. This fact implies that the wave arrives in phase along a certain aperture surrounding the impact position. To further investigate the behavior of this peculiar waveform, we rely on a more realistic simulation. We adopt a simulation approach proposed by Castaings et al. [19] and applied to IE by Baggens and Ryden [20]. The propagation of stress waves and the radiation of acoustic waves are studied by a finite element simulation in the frequency domain. The model consists of a plate of concrete (thickness 0.25 m) with an adjacent layer of air at the topside (Figure 2). The modeling was performed with a cylindrical symmetry (impact position in the center of symmetry) and a low reflecting boundary at the outer edges of the model. A free boundary was set at the lower surface of the model. A Gaussian monopuls with center frequency 15 kHz was used as the excitation source. Typical values were chosen for the elastic properties of concrete (Young’s modulus 36 GPa, density 2300 kg/m3, Poisson’s ratio 0.2).

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.