講演抄録/キーワード |
講演名 |
2008-11-27 14:45
キャリア超音波の音圧低減を目的としたパラメトリックスピーカ用位相反転駆動 ○菊地 哲・愛甲英寿・鎌倉友男・野村英之・酒井新一(電通大) US2008-63 |
抄録 |
(和) |
従来の動電型スピーカに比べて格段に鋭い指向性を持つパラメトリックスピーカは,その有用性が確認されているが,依然として超音波曝露の問題が残る.
超音波曝露を回避するため,音波を放射するために用いる超音波エミッタを 2 領域に分け,それぞれの放射器から同周波数で位相が異なる 1 次超音波を放射する.
これにより,得られるパラメトリック可聴音の音響特性を極力損なうことなく,
超音波音圧を 10~dB以上低減することができる. |
(英) |
An ultrasound source with a simple configuration is considered as a
theoretical model.
The source with a circular aperture consists of two coaxially arranged
planar projectors: i.e., one is an inner disc projector and the other is an outer ring projector.
The active areas of these projectors are the same.
The outer diameter of the source is 20 cm.
Both the projectors are driven individually at the same frequencies of 38 and 40 kHz but different phase angles.
Especially, the study focuses on two extreme cases of the usual in-phase driving and out-of-phase driving.
Numerical computation using the Khokhlov - Zabolotskaya - Kuznetsov (KZK)
equation demonstrates that when the driving signal is in phase the
difference frequency wave of a 2-kHz wave provides quite a narrow beam
a parametric acoustic array usually creates.
The beam has a similar directivity when the signal is out-of-phase by
180 degrees, although the peak of the sound pressure level decreases by
few decibels.
Interestingly, the second harmonic pressure level of the difference frequency reduces by 10~dB or more.
Needless to say, the pressure amplitudes of the primary waves are
suppressed considerably near the beam axis.
Experimental verification is done using an airborne ultrasound
source with a 19.2-cm circular aperture. |
キーワード |
(和) |
パラメトリックスピーカ / 超音波キャリア / 位相反転駆動 / 超音波曝露 / / / / |
(英) |
Parametric loudspeaker / Primary wave / Out-of-phase driving / Ultrasonic exposure / / / / |
文献情報 |
信学技報, vol. 108, no. 320, US2008-63, pp. 13-16, 2008年11月. |
資料番号 |
US2008-63 |
発行日 |
2008-11-20 (US) |
ISSN |
Print edition: ISSN 0913-5685 Online edition: ISSN 2432-6380 |
著作権に ついて |
技術研究報告に掲載された論文の著作権は電子情報通信学会に帰属します.(許諾番号:10GA0019/12GB0052/13GB0056/17GB0034/18GB0034) |
PDFダウンロード |
US2008-63 |