Paper Abstract and Keywords |
Presentation |
2008-11-27 14:45
Phase Inversion Driving for Reducing Carrier Ultrasound of Parametric Loudspeaker Satoshi Kikuchi, Hidetoshi Aiko, Tomoo Kamakura, Hideyuki Nomura, Shinichi Sakai (The University of Electro-Communications) US2008-63 |
Abstract |
(in Japanese) |
(See Japanese page) |
(in English) |
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. |
Keyword |
(in Japanese) |
(See Japanese page) |
(in English) |
Parametric loudspeaker / Primary wave / Out-of-phase driving / Ultrasonic exposure / / / / |
Reference Info. |
IEICE Tech. Rep., vol. 108, no. 320, US2008-63, pp. 13-16, Nov. 2008. |
Paper # |
US2008-63 |
Date of Issue |
2008-11-20 (US) |
ISSN |
Print edition: ISSN 0913-5685 Online edition: ISSN 2432-6380 |
Copyright and reproduction |
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US2008-63 |
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