Speaker system

Patent metadata

Field	Value
Publication number	US-9723412-B2
Application number	US-201514867128-A
Country	US
Kind code	B2
Filing date	Sep 28, 2015
Priority date	Mar 29, 2013
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

The present invention provides a speaker system comprising: an electroacoustic converter film composed of a polymeric composite piezoelectric body in which piezoelectric body particles are dispersed in a viscoelastic matrix formed of a polymer material that exhibits viscoelasticity at normal temperature, and thin film electrodes formed on both surfaces of the polymeric composite piezoelectric body; and a driving circuit that attenuates signal intensity of an input signal from a signal source at a rate of 5 dB to 7 dB per octave and supplies the attenuated input signal to the electroacoustic converter film.

First claim

What is claimed is:

1. A speaker system comprising:
an electroacoustic converter film composed of a polymeric composite piezoelectric body in which piezoelectric body particles are dispersed in a viscoelastic matrix formed of a polymer material that exhibits viscoelasticity at normal temperature, and thin film electrodes formed on both surfaces of the polymeric composite piezoelectric body; and
a driving circuit that attenuates signal intensity of an input signal from a signal source at a rate of 5 dB to 7 dB per octave and supplies the attenuated input signal to the electroacoustic converter film,
wherein a maximum value of a loss tangent (Tan δ) at a frequency of 1 Hz of the electroacoustic converter film, which is 0.1 or higher, is present at normal temperature.

2. The speaker system according to claim 1 ,
wherein the electroacoustic converter film has a protective layer that is formed on a surface of at least one of the thin film electrodes.

3. The speaker system according to claim 1 ,
wherein the driving circuit attenuates the signal intensity of the input signal at a rate of 6 dB per octave and supplies the attenuated input signal to the electroacoustic converter film.

4. The speaker system according to claim 3 ,
wherein the driving circuit includes a low pass filter that attenuates the signal intensity of the input signal of which a frequency is equal to or higher than a predetermined first cutoff frequency at a rate of 6 dB per octave, and a constant voltage type amplifier that amplifies the input signal.

5. The speaker system according to claim 4 ,
wherein the first cutoff frequency is a frequency lower than a lowest resonance frequency of the electroacoustic converter film.

6. The speaker system according to claim 1 ,
wherein the driving circuit includes a constant current type amplifier that amplifies the input signal.

7. The speaker system according to claim 4 ,
wherein the driving circuit further includes a high pass filter that attenuates the signal intensity of the input signal of which a frequency is equal to or lower than a predetermined second cutoff frequency.

8. The speaker system according to claim 7 ,
wherein the second cutoff frequency is equal to or lower than the first cutoff frequency.

9. The speaker system according to claim 6 ,
wherein the driving circuit further includes a high pass filter that attenuates the signal intensity of the input signal of which a frequency is equal to or lower than a predetermined second cutoff frequency.

10. The speaker system according to claim 1 , further comprising
a viscoelastic support that is disposed in close contact with at least one main surface of the electroacoustic converter film.

11. The speaker system according to claim 10 ,
wherein the viscoelastic support comprises at least one of glass wool, paper, polyurethane, a magnetic fluid, polyester wool, a coating material, and felt.

12. The speaker system according to claim 1 ,
wherein the polymer material is one or more selected from a group consisting of cyanoethylated polyvinyl alcohol, polyvinyl acetate, polyvinylidene chloride co-acrylonitrile, a polystyrene-vinyl polyisoprene block copolymer, polyvinyl methyl ketone, and polybutyl methacrylate.

13. The speaker system according to claim 1 ,
wherein the polymer material has a cyanoethyl group or a cyanomethyl group.

14. The speaker system according to claim 1 ,
wherein a storage modulus (E′) at a frequency of 1 Hz of the electroacoustic converter film that is obtained by dynamic viscoelasticity measurement is 10 GPa to 30 GPa at 0° C. and 1 GPa to 10 GPa at 50° C.

15. The speaker system according to claim 1 ,
wherein a product of a thickness of the electroacoustic converter film and a storage modulus (E′) at a frequency of 1 Hz of the electroacoustic converter film that is obtained by dynamic viscoelasticity measurement is 1.0×10 6 N/m to 2.0×10 6 N/m at 0° C. and 1.0×10 5 N/m to 1.0×10 6 N/m at 50° C.

16. The speaker system according to claim 1 ,
wherein a loss tangent (Tan δ) at a frequency of 1 kHz at 25° C. of the electroacoustic converter film is 0.05 or higher in a master curve obtained by dynamic viscoelasticity measurement.

Assignees

• Fujifilm Corp

Inventors

• Miyoshi Tetsu

Classifications

• H04R31/00

  Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor {(manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182)} · CPC title

• H04R17/005 Primary

  using a piezoelectric polymer · CPC title

• H04R2307/025

  Diaphragms comprising polymeric materials · CPC title

• H04R3/04

  for correcting frequency response · CPC title