| 摘要 |
An acoustic apparatus adapted to be heard only by a specific person or persons in one space without being worn by the user as in the case of an earphone. Sounds issuing from the apparatus do not leak to the outside and are not affected by the surrounding noise. Basically, the apparatus is arranged such that a sound source is disposed in one focus of a reflector having an ellipsoidal surface of revolution, and sounds are heard at the other focus. To increase the number of specific hearers, if the central portion of the reflector is made into a non-ellipsoidal surface of revolution, or a cross section having an ellipsoidal surface of revolution is extended orthogonally to the cross section by a predetermined length, the range of the other focus expands. In addition, by arranging a plurality of reflectors, it is possible to hear different sounds within the effective areas of the respective reflectors without mutual interference of the sounds.
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