| Project/Area Number |
17310096
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Social systems engineering/Safety system
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
KAMAKURA Tomoo The University of Electro-Communications, Faculty of Electro-Communications, Professor, 電気通信学部, 教授 (50109279)
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| Co-Investigator(Kenkyū-buntansha) |
NISHI Kazuki The University of Electro-Communications, Faculty of Electro-Communications, Associate Professor, 電気通信学部, 助教授 (00208125)
AOKI Kenichi The University of Electro-Communications, Faculty of Electro-Communications, Research Assistant, 電気通信学部, 助手 (30017412)
TOI Takeshi Chuo University, Faculty of Science and Engineering, Professor, 理工学部, 教授 (90286956)
鈴木 英男 千葉工業大学, 情報科学部, 教授 (50333018)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥10,100,000 (Direct Cost: ¥10,100,000)
Fiscal Year 2006: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 2005: ¥5,300,000 (Direct Cost: ¥5,300,000)
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| Keywords | Parametric loudspeaker / Weaver SSB modulator / Digital power amplifier / Pedestrian signal / 音環境 / SSB / ウエーバー(Weaver)方式 / D級アンプ |
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| Research Abstract |
A highly directional loudspeaker like a spotlight is actually realized by the self-demodulation effect of an intense airborne ultrasound amplitude-modulated by audio signals. This loudspeaker, which is usually called a parametric loudspeaker in acoustics, is based on the generation of a parametric array (in addition, virtual and end-fire array) in the beam space, and is able to transmit faithfully audio sounds to a specific area that cannot be detected by people in adjacent locations. The most remarkable and interesting property of the difference frequency component or parametric array is its sharp directivity that cannot be realized by any conventional loudspeakers with the same aperture size. Additionally, the side-lobes that usually exist for a directive sound source are suppressed considerably. According to our previous research on a parametric loudspeaker, three problems remain unsolved for practical applications. The problems are summarized as follows. First, to reduce harmonic d
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istortion in parametric sounds as much as possible, appropriate signal processing is needed in driving the parametric loudspeaker. Under the financial supports from the Grants-in-Aid for Scientific Research, we, in collaboration with Mitsubishi Electric Engineering Company, have worked during two years to reduce the distortion by means of a suitable modulation of the carrier intense ultrasound. The method is based on a single-side band (SSB) modulation with the carrier whose amplitude is dynamically changed in proportional to an input audio signal. This dynamic SSB modulation then achieves less distortion as well as less electric power consumption in working the parametric loudspeaker. The modulator is realized through digital circuit technology so as to adjust its modulation functions accurately and readily. Second, to reduce electric power consumption, they are now developing a digital power amplifier to drive the loudspeaker with power saving. We confirm that our preliminary experiments using a digital power amplifier demonstrate that the power consumption is reduced more than 75 % incomparison with a analog power amplifier. This technology is also of importance for further developing the parametric loudspeaker. Finally, we have to develop an airborne ultrasonic transducer that radiates an intense and a relatively wide-band carrier wave. Additionally, the transducer requires high conversion efficiency from electric power to ultrasonic power and robustness in mechanics. The last problem is a next step for research project, and would be overcome by new technology such as MEMS, thus creating better products with good sound and electric performances. Less
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