PROBLEM TO BE SOLVED: To avoid the occurrence of sound leaking from a headphone device to the outside.
SOLUTION: An inner type headphone device has a cylindrical casing 1 inserted into human ear and a small speaker 2 in a shape that is substantially along an internal diameter of the casing 1 is provided toward an open end on the side of the inserting direction of the cylindrical casing 1. Then, a ring-like piezoelectric element (for example, a piezo-element) 3 in a shape substantially along the internal diameter of the casing 1 on the rear side of the small speaker, namely, the side opposite to the inserting direction of the casing 1 into the ear and a diaphragm member 4 is adhered to the piezoelectric element 3. By driving the diaphragm member 4 in a phase reverse to that of the small speaker 2, sound waves emitted from the small speaker 2 are offset, and leakage of sound to the rear side (outside) of the small speaker 2 which is the outside is prevented.
- 国立大学法人九州工業大学 オープンイノベーション推進機構 産学官連携本部
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