{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T05:12:50Z","timestamp":1774329170801,"version":"3.50.1"},"reference-count":41,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2020,12,16]],"date-time":"2020-12-16T00:00:00Z","timestamp":1608076800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008530","name":"European Regional Development Fund","doi-asserted-by":"publisher","award":["01.2.2-LMT-K-718-03-0026"],"award-info":[{"award-number":["01.2.2-LMT-K-718-03-0026"]}],"id":[{"id":"10.13039\/501100008530","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Air-coupled ultrasonic probes require a special design approach and handling due to the significant mismatch to the air. Outer matching layers have to be soft so can be easily damaged and excitation voltages might cause the degradation of electrodes or bonding between the layers. Integrity inspection is desired during design, manufacturing, and exploitation. Spatial distribution of a transduction efficiency over piezoelement surface is proposed as a convenient means for the air-coupled probe integrity inspection. Focused transducer of similar center frequency is used to scan the surface of the inspected probe. However, such approach creates a challenge, i.e., area of the scanning beam is much smaller than the total receiving area of the inspected probe, therefore, contrast and imaging resolution are significantly degraded. Masking aperture made from cardboard and felt, placed at the focal point was proposed as solution. Far-range sidelobes were suppressed down to the noise floor (\u221250 dB) and the near-range sidelobes were reduced down to \u221217 dB. The proposed modification allows to use a similar frequency focused transducer. Probe integrity inspection can be carried out at significantly enhanced contrast and lateral resolution. Natural and artificial defects can be detected by the use of the proposed method.<\/jats:p>","DOI":"10.3390\/s20247196","type":"journal-article","created":{"date-parts":[[2020,12,16]],"date-time":"2020-12-16T09:21:15Z","timestamp":1608110475000},"page":"7196","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Air-Coupled Ultrasonic Probe Integrity Test Using a Focused Transducer with Similar Frequency and Limited Aperture for Contrast Enhancement"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5555-0323","authenticated-orcid":false,"given":"Linas","family":"Svilainis","sequence":"first","affiliation":[{"name":"Department of Electronics Engineering, Kaunas University of Technology, LT-51368 Kaunas, Lithuania"}]},{"given":"Andrius","family":"Chaziachmetovas","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, Kaunas University of Technology, LT-51368 Kaunas, Lithuania"}]},{"given":"Darius","family":"Kybartas","sequence":"additional","affiliation":[{"name":"Department of Electronics Engineering, Kaunas University of Technology, LT-51368 Kaunas, Lithuania"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1971-7402","authenticated-orcid":false,"given":"Tomas","family":"Gomez Alvarez-Arenas","sequence":"additional","affiliation":[{"name":"Instituto de Tecnologias F\u00edsicas y de la Informaci\u00f3n, CSIC, 28006 Madrid, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1804","DOI":"10.1016\/j.ultras.2014.02.006","article-title":"Review of air-coupled ultrasonic materials characterization","volume":"54","author":"Chimenti","year":"2014","journal-title":"Ultrasonics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1016\/j.ultras.2015.08.011","article-title":"Non-contact ultrasonic technique for Lamb wave characterization in composite plate","volume":"64","author":"Harb","year":"2016","journal-title":"Ultrasonics"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"De\u00e1n-Ben, X.L., Pang, G.A., Montero de Espinosa, F., and Razansky, D. 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