TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Beck, Uwe A1 - Lange, Thorid A1 - Weise, Matthias T1 - A resonance-free nano-film airborne ultrasound emitter N2 - In this contribution we present a novel thermo-acoustic approach for the generation of broad band airborne ultrasound and investigate the applicability of resonance-free thermo-acoustic emitters for very short high pressure airborne ultrasound pulses. We report on measurements of thermo-acoustic emitter consisting of a 30 nm thin metallic film on a usual soda-lime glass substrate, generating sound pressure values of more than 140 dB at 60 mm distance from the transducer and compare the results with conventional piezoelectric airborne ultrasound transducers. Our experimental investigations show that such thermo-acoustic devices can be used as broad band emitters using pulse excitation. T2 - 39th Annual review of progress in quantitative nondestructive evaluation CY - Denver, Colorado, USA DA - 2012-07-15 KW - Thermo-acoustic KW - Broad band airborne ultrasound KW - High pressure airborne ultrasound KW - Resonance free ultrasound transducer KW - Broad band ultrasonic emitter KW - Measurement sound particle velocity PY - 2013 SN - 978-0-7354-1129-6 U6 - https://doi.org/10.1063/1.4789225 SN - 0094-243X SN - 1551-7616 N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings VL - 1511 SP - 1541 EP - 1546 AN - OPUS4-27790 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daschewski, Maxim A1 - Boehm, Rainer A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Harrer, Andrea T1 - Physics of thermo-acoustic sound generation N2 - We present a generalized analytical model of thermo-acoustic sound generation based on the analysis of thermally induced energy density fluctuations and their propagation into the adjacent matter. The model provides exact analytical prediction of the sound pressure generated in fluids and solids; consequently, it can be applied to arbitrary thermal power sources such as thermophones, plasma firings, laser beams, and chemical reactions. Unlike existing approaches, our description also includes acoustic near-field effects and sound-field attenuation. Analytical results are compared with measurements of sound pressures generated by thermo-acoustic transducers in air for frequencies up to 1 MHz. The tested transducers consist of titanium and indium tin oxide coatings on quartz glass and polycarbonate substrates. The model reveals that thermo-acoustic efficiency increases linearly with the supplied thermal power and quadratically with thermal excitation frequency. Comparison of the efficiency of our thermo-acoustic transducers with those of piezoelectric-based airborne ultrasound transducers using impulse excitation showed comparable sound pressure values. The present results show that thermo-acoustic transducers can be applied as broadband, non-resonant, high-performance ultrasound sources. KW - Thermophone KW - Ionophone KW - Thermo-acoustic effect KW - Non resonant ultrasound source PY - 2013 U6 - https://doi.org/10.1063/1.4821121 SN - 0021-8979 SN - 1089-7550 VL - 114 SP - 114903-1 - 114903-12 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-29278 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Harrer, Andrea A1 - Daschewski, Maxim A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Guderian, Matthias A1 - Meyer-Plath, Asmus T1 - Thermoacoustic generation of airborne ultrasound using carbon materials at the micro- and nanoscale N2 - The generation of airborne ultrasound is presented using the thermoacoustic principle applied to carbon materials at the micro- and nanoscale. Such materials are shown to be capable of emitting ultrasound when being fed by an alternating current. We tested the acoustic performance of carbon fibers, bucky papers and electrospun polyacrylonitrile-derived carbon nanofibers and determined the sound pressure for frequencies up to 350 kHz. A comparison between the experimental results and the theoretical prediction showed remarkable agreement for frequencies up to 150 kHz. Beyond 150 kHz, we found slight deviations from the expected sound pressure dependence on the square root of the frequency. KW - Thermoacoustic KW - Airborne ultrasound transducer KW - Sound pressure PY - 2012 U6 - https://doi.org/10.3233/JAE-2012-1440 SN - 1383-5416 SN - 0925-2096 VL - 39 IS - 1-4 SP - 35 EP - 41 PB - IOS Press CY - Amsterdam, The Netherlands AN - OPUS4-26737 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Guderian, Matthias A1 - Meyer-Plath, Asmus ED - Linde, B. B. J. ED - Paczkowski, J. ED - Ponikwicki, N. T1 - Carbon nanomaterials as broadband airborne ultrasound transducer N2 - A method has been developed for the generation of airborne ultrasound using the thermoacoustic principle applied to carbon materials at the micro- and nanoscale. Such materials are shown to be capable to emitting the ultrasound. We tested the acoustic performance of electrospun polyacrylonitrile-derived carbon nanofibers tissues and determined the sound pressure for frequencies up to 350 kHz. The experimental results are compared to analytic calculations. T2 - International congress on ultrasonics CY - Gdansk, Poland DA - 2011-09-05 KW - Thermoacoustic KW - Airborne ultrasound transducer KW - Sound pressure PY - 2012 SN - 978-0-7354-1019-0 U6 - https://doi.org/10.1063/1.3703262 SN - 0094-243X N1 - Serientitel: AIP conference proceedings – Series title: AIP conference proceedings IS - 1433 SP - 624 EP - 627 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-26788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Daschewski, Maxim A1 - Harrer, Andrea A1 - Prager, Jens A1 - Kreutzbruck, Marc A1 - Beck, Uwe A1 - Lange, Thorid A1 - Weise, Matthias T1 - Metallic nanofilm as resonance-free airborne ultrasound emitter N2 - A novel approach for the generation of broadband airborne ultrasound by using the thermo-acoustic effect is presented in this contribution. We investigate the applicability of resonance-free thermo-acoustic emitters for generation of very short high pressure airborne ultrasound pulses. A thermoacoustic emitter consisting of a 30 nm thin metallic film on a usual soda-lime glass substrate generates sound pressure values of more than 140 dB at 60 mm distance. The results are compared with conventional piezoelectric airborne ultrasound transducers. Our investigations show the applicability of the thermo-acoustic devices for broadband and high pressure ultrasound emitters using pulse excitation. T2 - 2012 IEEE International Ultrasonics Symposium (IUS) CY - Dresden, Germany DA - 2012-10-07 KW - Thermo-acoustic KW - Broadband airborne ultrasound KW - Resonance-free ultrasound transducer KW - High pressure airborne ultrasound KW - Sound particle velocity measurement PY - 2012 SN - 978-1-4673-4562-0 U6 - https://doi.org/10.1109/ULTSYM.2012.0241 SN - 1948-5719 SP - 965 EP - 967 AN - OPUS4-29152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daschewski, Maxim A1 - Kreutzbruck, Marc A1 - Prager, Jens A1 - Dohse, Elmar A1 - Gaal, Mate A1 - Harrer, Andrea T1 - Resonanzfreie Messung und Anregung von Ultraschall N2 - In diesem Beitrag präsentieren wir innovative Methoden für die breitbandige und resonanzfreie Messung und Anregung von Ultraschall. Das Messverfahren verwendet eine Kunststofffolie und ein Laser-Vibrometer als breitbandigen und resonanzfreien Empfänger. Im Allgemeinen ermöglicht dieses Verfahren eine präzise Messung der Schallschnelle und des Schalldruckes in beliebigen, für das Laserlicht transparenten Flüssigkeiten und Gasen mit bekannter Dichte und Schallgeschwindigkeit. Das resonanzfreie Senden von Ultraschall basiert auf einem elektro-thermo-akustischen Wandlerprinzip und ermöglicht, im Gegensatz zu herkömmlichen Ultraschallwandlern, die Erzeugung von beliebig geformten akustischen Signalen ohne Resonanzen und ohne Nachschwingen. N2 - In this contribution we present innovative methods for broadband and resonance-free sensing and emitting of ultrasound. The sensing method uses a polyethylene foil and a laser vibrometer as a broadband and resonance-free sound receiver. In general, this method enables absolute measurement of sound particle velocity and sound pressure in arbitrary, laser beam transparent liquids and gases with known density and sound velocity. The resonance-free emitting method is based on the electro-thermo-acoustic principle and enables, contrary to conventional ultrasound transducers, generation of arbitrary shaped acoustic signals without resonances and post-oscillations. KW - Ultraschall KW - Übertragungsfunktion KW - Charakterisierung von Ultraschallmesssystemen KW - Thermo-akustische Ultraschallemitter KW - Ultrasound KW - Transfer function KW - Characterization of ultrasonic measurement systems KW - Thermo-acoustic ultrasound emitter PY - 2015 U6 - https://doi.org/10.1515/teme-2014-0020 SN - 0340-837X SN - 0178-2312 SN - 0171-8096 VL - 82 IS - 3 SP - 156 EP - 166 PB - Oldenbourg CY - München AN - OPUS4-32733 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -