Near-field characteristics of the parametric loudspeaker using ultrasonic transducers |
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Authors: | Hyeong Sick Ju [Author Vitae] |
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Affiliation: | a Graduate Program in Acoustics, The Pennsylvania State University, 201 Applied Science Building, University Park, PA 16802, USA b Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejon 305-701, Republic of Korea |
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Abstract: | A parametric speaker is a device for generating and focusing highly directional sound beams. It is essentially a by-product that comes with the nonlinearity of ultrasound. It is noteworthy that this directional beam was controlled and utilized mostly for far-field applications in the past. We empirically study the directivity and attenuation characteristics of the parametric loudspeaker in the near-field where we desire to use it. Physical parameters for experiments are imported from a theoretical model based on the far-field approximation. The findings are that increases in aperture size and modulation frequency cause higher directivity, but have more than twice the beamwidth of the far-field approximation. The attenuation also does not obey the inverse-square law which describes far-field spreading from acoustic sources. The results conclusively explain a series of formation and attenuation of the virtual sound sources and define limitations of use in the near-field. |
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Keywords: | Parametric loudspeaker Near-field Directivity Attenuation Spurious signal |
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