| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the size and cost of an active muffler by increasing the degrees of freedom at the arranged position of a large member of which speakers are conventionally could not always be placed at a duct end to output an antinoise sound wave or by arranging them in a position, where they can provide efficient noise reduction and reducing their member required for necessary noise reducing effect. SOLUTION: Filter circuits 7, 8 are interposed at least either between a first sound wave sensor 4 and a controller 5 or between a second sound wave sensor 6 and the controller 5. A speaker 3 is arranged midway of an exhaust pipe 1, in which a passive muffler 11 is interposed, and the speaker 3 is located upstream of the passive muffler 11.</p> |
