title: Ultrasound radiation from a three-layer thermoacoustic transformation device.
abstract: A thermophone is a thermoacoustic transducer, which generates sound via time-varying Joule heating of an electrically conductive layer, which leads to expansion and contraction of a small pocket of air near the surface of the film. In this work, a 10-μm-thick Ag-Pd conductive film was coupled with heat-insulating and heat-releasing layers to fabricate a three-layer thermophone for generating ultrasound. The heat-insulating layer was 47 μm thick, and was made of glass. The heat-releasing layer was 594 μm thick, and was made of 94% alumina. Because of the simple sound-generation mechanism, which does not require mechanical moving parts, the Ag-Pd conductive film on the glass substrate can produce ultrasound radiation with broadband frequency characteristics, where exiting commercial electrode materials were used. We also demonstrate that the measured directivity patterns are in good agreement with theoretical predictions, assuming a rectangular diaphragm with the same size as the metallic film.
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan. Electronic address: dmn1026@mail4.doshisha.ac.jp.
authors.forename: Takuya
authors.initials: T
authors.lastname: Nishioka
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan. Electronic address: dmo1040@mail4.doshisha.ac.jp.
authors.forename: Yu
authors.initials: Y
authors.lastname: Teshima
authors.affiliation: Murata Manufacturing Co., Ltd., Nagaokakyo 617-8555, Japan. Electronic address: mano@murata.co.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Mano
authors.affiliation: Murata Manufacturing Co., Ltd., Nagaokakyo 617-8555, Japan. Electronic address: kensakai@murata.co.jp.
authors.forename: Ken
authors.initials: K
authors.lastname: Sakai
authors.affiliation: Murata Manufacturing Co., Ltd., Nagaokakyo 617-8555, Japan. Electronic address: asada@murata.co.jp.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Asada
authors.affiliation: Faculty of Science and Engineering, Doshisha University, Kyotanabe 610-0321, Japan. Electronic address: mmatsuka@mail.doshisha.ac.jp.
authors.forename: Mami
authors.initials: M
authors.lastname: Matsukawa
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan. Electronic address: tota@mail.doshisha.ac.jp.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ohta
authors.affiliation: Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan. Electronic address: shiryu@mail.doshisha.ac.jp.
authors.forename: Shizuko
authors.initials: S
authors.lastname: Hiryu
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D004867:Equipment Design; D005898:Glass / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008962:Models, Theoretical; D012834:Silver / Q000737:chemistry*; D013016:Sound; D013499:Surface Properties; D014159:Transducers; D014465:Ultrasonics / Q000295:instrumentation*; D014732:Vibration
chemical_list: D007854:Lead; D012834:Silver; D000537:Aluminum Oxide
keywords: Broadband; Thermoacoustic transformation; Thermophone; Three-layer structure; Ultrasound emission