| 摘要 |
PROBLEM TO BE SOLVED: To suppress vibrations to a rear side at the time of sound generation and to improve discharge sound quality by allowing a duct, which has an opening on the rear of a loudspeaker unit having a diaphragm that generates sound with vibrations and which is tubularly formed, to satisfy a specific relationship among air mass in the duct, acceleration for the air to move, diaphragm mass and the acceleration. SOLUTION: A duct 4 is tubularly arranged on a loudspeaker unit 1 with its center on the same line as the center of diaphragm 18. Here, the duct 4 is formed so that the relationship: mDαD=AM0 d0 is satisfied where mass of the diaphragm 18 is m0 , the acceleration at the time of vibration isα0 , air mass in the duct 4 is mD and air acceleration at the time of vibrations isαD. In such cases, the duct 4 can absorb discharge vibration waves of a vibration system 10 by making the force of vibration waves from a speaker unit 3 equal to the air discharge force of the duct 4 to the outside, where A is assumed to be one. However, the vibration waves from the unit 3 is suppressed with A in a range of 0.5 to 1.5, considering the errors of the unit 3 and the duct 4.
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