| 摘要 |
Sound waves from a plate-shaped acoustic source, which generates fundamental waves (sound waves) having at least two frequencies, propagate through a propagating portion. The propagating portion consists of a medium in which a non-linear interaction is induced by the fundamental waves. A secondary sound wave having a frequency conforming to the difference between the two fundamental waves is generated by the medium. Fundamental wave components other than the secondary sound wave are absorbed by an acoustic absorber so that only the secondary sound wave is delivered as an output. The acoustic source, propagating portion and acoustic absorber are substantially transparent and stacked in three layers. This allows the resulting acoustic output device to be incorporated in the display unit of an electronic apparatus.
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