• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.545-550
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• 2005

A parametric loudspeaker is a device to generate highly directional sound using ultrasounds. The parametric loudspeaker could be used to focus sound in a limited space, so it is important to study the characteristics of the parametric loudspeaker in near-field. Mechanism of the audible sound generation in the parametric loudspeaker is explained by nonlinear interaction of the ultrasounds and is modeled as KZK equation, the nonlinear wave equation which contains attenuation, nonlinearity and diffraction. To measure the directional characteristics of the parametric loudspeaker precisely, a method to reduce the spurious signal which taints the measured signal was invented. With the method, directivity patterns of the parametric loudspeaker were measured and compared to the approximated solution and piston sources.

• The Journal of the Acoustical Society of Korea
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• v.24 no.3E
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• pp.90-98
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• 2005

Enhanced approach using computational and experimental method is proposed and performed to describe very well the behavior of loudspeaker than conventional method. Proposed procedure is composed of four parts. First, Thiele-Small parameters for test loudspeaker are identified by an electrical impedance method like as a delta mass method. Second part includes the processes to measure physical properties. Physical data like masses and thicknesses of loudspeaker's components are measured by an electrical precision scale and a digital vernier caliper. Third, the identified Thiele-Small parameters are proposed to be used as load boundary conditions for vibration analysis instead of electromagnetic circuit analysis to get a driving force upon bobbin part. Also, these parameters and physical data are used to modify physical properties required for computation to accommodate simulated sound pressure level with measured one for loudspeaker enclosure system. These data like as Young's modulus and thickness for a diaphragm are required for vibration analysis of loudspeaker but not measured accurately. Finally, it was investigated that simulated sound pressure level with full acoustic modeling including an acoustic port for test loudspeaker agreed with experimental result very well in the midrange frequency band(from 100 Hz to 2,000 Hz). In addition, several design parametric study is performed to grasp acoustical behaviors of loudspeaker system due to variations of diaphragm thicknesses and shapes of dust cap.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.515-518
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• 2004

파라메트릭 라우드스피커(parametric loudspeaker)는 초음파의 지향성 발생 특성과 발생된 초음파의 비선형 전파 현상을 이용하여 간접적으로 가청음을 발생시키는 기술을 이용한다. 이를 이용하면 소리를 직진 형태로 전파 시킬 수 있기 때문에 원하는 영역에만 음향 신호를 전달할 수 있다. 본 연구에서는 파라메트릭 라우드스피커의 연구 진행 상황을 간략히 살펴보고, 현재 이 분야에서 가장 실용적인 초음파 발생기 방식으로 알려진 압전 필름형 초음파 발생기의 디자인 기술과 이를 적용한 파라메트릭 라우드스피커에 관하여 논한다. 그리고 이러한 스피커 시스템이 실용화되기 위해 해결해야 하는 문제점을 살펴본다.