US 12,456,449 B2
Active noise control system
Kohei Oto, Osaka (JP); Yusuke Komoto, Osaka (JP); Ryohei Oban, Osaka (JP); Saori Yamamoto, Osaka (JP); Yoshinobu Kajikawa, Osaka (JP); and Shun Hirose, Osaka (JP)
Assigned to NITTO DENKO CORPORATION, Osaka (JP); and THE SCHOOL CORPORATION KANSAI UNIVERSITY, Osaka (JP)
Appl. No. 17/595,617
Filed by NITTO DENKO CORPORATION, Ibaraki (JP); and THE SCHOOL CORPORATION KANSAI UNIVERSITY, Suita (JP)
PCT Filed Apr. 2, 2020, PCT No. PCT/JP2020/015246
§ 371(c)(1), (2) Date Nov. 19, 2021,
PCT Pub. No. WO2020/235231, PCT Pub. Date Nov. 26, 2020.
Claims priority of application No. 2019-094731 (JP), filed on May 20, 2019.
Prior Publication US 2022/0223136 A1, Jul. 14, 2022
Int. Cl. G10K 11/178 (2006.01)
CPC G10K 11/17881 (2018.01) [G10K 11/17825 (2018.01); G10K 11/17853 (2018.01); G10K 11/17857 (2018.01)] 5 Claims
OG exemplary drawing
 
1. An active noise control system comprising:
a structure;
a speaker attached to the structure, wherein
the speaker includes a radiation surface, a piezoelectric film, and an interposed layer,
the interposed layer is disposed between the structure and the piezoelectric film, and
the interposed layer is at least one of a porous body layer or a resin layer,
the radiation surface has a first region, a second region, and a third region between the first region and the second region, and
a period appears during which a first wavefront propagates toward a reference axis so as to increase a distance between a first normal line and the first wavefront and during which a second wavefront propagates toward the reference axis so as to increase a distance between a second normal line and the second wavefront, wherein further
the first wavefront is a wavefront formed by the speaker to propagate from the first region,
the second wavefront is a wavefront formed by the speaker to propagate from the second region,
the first normal line is a normal line perpendicular to the first region,
the second normal line is a normal line perpendicular to the second region, and
the reference axis is an axis perpendicular to the third region and extending away from the radiation surface;
a controller, wherein
a certain frequency range is set in the controller,
the controller controls a frequency of sound to be output from the speaker to have a value within the frequency range, wherein further
when a wavelength of sound having an upper limit frequency of the frequency range is defined as a reference wavelength and the radiation surface is viewed in a plan view,
the radiation surface has a first end portion and a second end portion facing each other,
a first margin between the first end portion and an end portion of the structure is 0 or more and ⅓ or less of the reference wavelength, and
a second margin between the second end portion and an end portion of the structure is 0 or more and ⅓ or less of the reference wavelength,
an error microphone;
a reference microphone; and
wherein
the structure is disposed between the reference microphone and the error microphone,
the speaker is disposed between the structure and the error microphone,
the controller further performs feedforward control of controlling sound output from the speaker based on an output signal of the reference microphone and an output signal of the error microphone, and
the controller has at least one amplifier, at least one low-pass filter, at least one analog-to-digital converter, and at least one digital-to-analog converter.