An automated interferometric stand (AIS) was created to determine the amplitude-frequency characteristics of acoustic emitters in the range from 0.5 to 200 kHz. The created AIS contains a unit for generating acoustic sinusoidal excitation pulse packets and a recording unit. The unit for generating acoustic pulse packets includes a generator of sinusoidal signals, a microprocessor unit for pulse packets generation and the AIS synchronization, a power amplifier of a sinusoidal signal to create a sufficient power of the acoustic emitter excitation signal. The recording unit includes a Michelson interferometer with a sound-conducting rod in one of the arms. One of the ends of the rod has a mirror surface. The other end is connected to the acoustic emitter through an acoustic contact. The length of the sound-conducting rod is 50 cm, which is enough to ensure measurements at the lower limit of the frequency range of the acoustic emitter radiation. The propagation time of the acoustic wave in the rod is of the order of 75 microseconds. As the end of the rod vibrates due to acoustic excitation, the initial path difference of the optical beams in the interferometer will change, causing a change in the intensity of the illumination produced by the interfering beams. These changes are recorded by photodiode in the other arm of the interferometer. After the photodiode signal is amplified in the amplifier, it is fed to the analog-to-digital converter, the output of which is transferred to the buffer memory, where the discretized values of the response signal amplitude during the time of the measuring pulse are accumulated. The control algorithm of the AIS is carried out with the help of developed software. The results of measuring the amplitude-frequency characteristics of mass-produced broadband acoustic emitters using AIS proved the satisfactory convergence of the obtained frequency responses with the passport data of these serial devices frequency responses. The amplitude-frequency characteristic of experimental sample of a piezoelectric acoustic emitter, made for research on the detection and identification of internal defects in laminated composite structures and "composite-concrete" adhesive joints, was obtained.

1. Kang, Y.K.; Park, H.C.; Kim, J.; Choi S.B. Interaction of active and passive vibration control of laminated composite beams with piezoceramic sensors/actuators. Mater. Des. 2002, 23(3), 277-286. https://doi.org/10.1016/S0261-3069(01)00081-4

2. Liu, S.; Sun, W.; Jing, H.; Dong, Z. Debonding detection and monitoring for CFRP reinforced concrete beams using piezoceramic sensors. Materials. 2019, 12(13), 2150. https://doi.org/10.3390/ma12132150

3. Qiu Q. Imaging techniques for defect detection of fiber reinforced polymer bonded civil infra-structures. Structural Control Health Monititoring. 2020, 27, e2555. https://doi.org/10.1002/stc.2555

4. Wang, L.S.; Krishnaswamy S. Additive-subtractive speckle interferometry: extraction of phase data in noisy environments. Optical Engineering. 1996, 35(3), 794-801. https://doi.org/10.1117/1.600649

5. Fomitchov, P.; Wang, L.S.; Krishnaswamy S. Advanced image-processing techniques for auto-matic nondestructive evaluation of adhesively-bonded structures using speckle interferometry. Journal Nondestruct. Evaluation. 1997, 16, 215-127. https://doi.org/10.1023/A:1021848031529

6. Lai, W.L.; Kou, S.C.; Poon, C.S.; Tsang, W.F.; Ng, S.P.; Hung, Y.Y. Characterization of flaws embedded in externally bonded CFRP on concrete beams by infrared thermography and shearography. Journal Nondestruct. Evaluation. 2009, 28, 27-35. https://doi.org/10.1007/s10921-009-0044-x

7. Qiu, Q.; Lau, D. Measurement of structural vibration by using optic-electronic sensor. Measurement. 2018, 117, 435-443. https://doi.org/10.1016/j.measurement.2017.12.040

8. Nazarchuk, Z.T.; Muravsky, L.I.; Kuts, O. G. Nondestructive testing of thin composite structures for subsurface defects detection using dynamic laser speckles. Residual Nondestive Evaluation. 2022, 33, 59-77. https://doi.org/10.1080/09349847.2022.2049407

9. Nazarchuk, Z.; Muravsky, L.; Kuryliak, D. Methods for processing and analyzing the speckle patterns of materials surfaces. In: Optical metrology and optoacoustics in nondestructive evalua-tion of materials; Nazarchuk, Z., Muravsky, L., Kuryliak, D. Eds.; Springer Nature, 2023; pp 249-323. https://doi.org/10.1007/978-981-99-1226-1_6