{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,8]],"date-time":"2026-01-08T10:14:10Z","timestamp":1767867250893,"version":"3.49.0"},"reference-count":21,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2023,1,26]],"date-time":"2023-01-26T00:00:00Z","timestamp":1674691200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Air-coupled ultrasound sensors have advantages over contact ultrasound sensors when a sample should not become contaminated or influenced by the couplant or the measurement has to be a fast and automated inline process. Thereby, air-coupled transducers must emit high-energy pulses due to the low air-to-solid power transmission ratios (10\u22123 to 10\u22128). Currently used resonant transducers trade bandwidth\u2014a prerequisite for material parameter analysis\u2014against pulse energy. Here we show that a combination of a non-resonant ultrasound emitter and a non-resonant detector enables the generation and detection of pulses that are both high in amplitude (130 dB) and bandwidth (2 \u00b5s pulse width). We further show an initial application: the detection of reflections inside of a carbon fiber reinforced plastic plate with thicknesses between 1.7 mm and 10 mm. As the sensors work contact-free, the time of flight and the period of the in-plate reflections are independent parameters. Hence, a variation of ultrasound velocity is distinguishable from a variation of plate thickness and both properties are determined simultaneously. The sensor combination is likely to find numerous industrial applications necessitating high automation capacity and opens possibilities for air-coupled, single-side ultrasonic inspection.<\/jats:p>","DOI":"10.3390\/s23031379","type":"journal-article","created":{"date-parts":[[2023,1,27]],"date-time":"2023-01-27T01:27:58Z","timestamp":1674782878000},"page":"1379","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Broadband Air-Coupled Ultrasound Emitter and Receiver Enable Simultaneous Measurement of Thickness and Speed of Sound in Solids"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2520-4697","authenticated-orcid":false,"given":"Klaas","family":"Bente","sequence":"first","affiliation":[{"name":"Bundesanstalt f\u00fcr Materialforschung und -pr\u00fcfung BAM, 8.4 Acoustic and Electromagnetic Methods, Unter den Eichen 87, 12205 Berlin, Germany"},{"name":"Health and Medical University, Olympischer Weg 1, 14471 Potsdam, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Janez","family":"Rus","sequence":"additional","affiliation":[{"name":"Chair of Non-Destructive Testing, Centre for Building Materials, Technical University of Munich, Franz-Langinger-Stra\u00dfe 10, 81245 Munich, Germany"},{"name":"Laboratory of Wave Engineering, Swiss Federal Institute of Technology Lausanne, Station 11, 1015 Lausanne, Switzerland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hubert","family":"Mooshofer","sequence":"additional","affiliation":[{"name":"Siemens AG, Corporate Technology, Otto-Hahn-Ring 6, 81739 M\u00fcnchen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1464-9818","authenticated-orcid":false,"given":"Mate","family":"Gaal","sequence":"additional","affiliation":[{"name":"Bundesanstalt f\u00fcr Materialforschung und -pr\u00fcfung BAM, 8.4 Acoustic and Electromagnetic Methods, Unter den Eichen 87, 12205 Berlin, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7956-0558","authenticated-orcid":false,"given":"Christian Ulrich","family":"Grosse","sequence":"additional","affiliation":[{"name":"Chair of Non-Destructive Testing, Centre for Building Materials, Technical University of Munich, Franz-Langinger-Stra\u00dfe 10, 81245 Munich, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1016\/S0041-624X(98)00034-1","article-title":"Air-coupled ultrasonic testing of metals using broadband pulses in through-transmission","volume":"37","author":"Wright","year":"1998","journal-title":"Ultrasonics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1016\/S0041-624X(00)00059-7","article-title":"The use of broadband acoustic transducers and pulse-compression techniques for air-coupled ultrasonic imaging","volume":"39","author":"Gan","year":"2001","journal-title":"Ultrasonics"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1016\/j.ultras.2014.08.021","article-title":"Air-coupled ultrasonic through-transmission thickness measurements of steel plates","volume":"56","author":"Waag","year":"2015","journal-title":"Ultrasonics"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1527","DOI":"10.1007\/s00226-018-1052-8","article-title":"Air-coupled ferroelectret ultrasonic transducers for nondestructive testing of wood-based materials","volume":"52","author":"Gaal","year":"2018","journal-title":"Wood Sci. 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