Electro-acoustic transducer element
AssigneeToray Industries, Inc.
InventorsHiroji Ohigashi, Joshiharu Nakanishi, Miyo Suzuki
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Abstract
Electro-acoustic transducer element having its resonant frequency in a lower frequency range advantageously usable for diagnostic purposes comprises a polymeric piezoelectric film such as polyvinylidene fluoride film being coupled with an additional layer having a thickness specified in relation to the wavelength of sound waves within the additional layer at the free resonant frequency of the polymeric piezoelectric film, the additional layer having an acoustic impedance related to the acoustic impedance of the polymeric piezoelectric film.
Claims14
An improved electro-acoustic transducer element comprising
- a polymeric piezoelectric film having an acoustic impedance Z.sub.o,
- elements functioning as electrodes for the film,
- an additional layer having an acoustic impedance Z coupled to the acoustic emanation side of the film and having a thickness of from 0.5 .mu.m to 3.lambda./8 in which .lambda. refers to the wavelength of sound waves within the additional layer at the free resonant frequency of the film, and
- the acoustic impedance Z of the additional layer being not less than two times the acoustic impedance Z.sub.o of the film.
An improved electro-acoustic transducer element comprising
- a polymeric piezoelectric film having acoustic impedance Z.sub.o,
- elements functioning as electrodes for the film,
- an additional comparatively thin layer having an acoustic impedance Z coupled to the side opposite to the acoustic emanation side of the film and having a thickness less than the film and of from 0.5 .mu.m to 1.lambda./16 in which .lambda. refers to the wavelength of sound waves in the additional layer at the free resonant frequency of the film, and the acoustic impedance Z of the additional layer being not less than two times the acoustic impedance Z.sub.o of the film.
Dependencies are inferred from the claim text.