| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an active silencer in which coherence lowering can be suppressed and a high silencing effect can be obtained by lowering influence of an air flow on a microphone even in a ventilation flue in which an air velocity is high.SOLUTION: Defining a wall plane of an air duct 1 as a reference plane 8, a reference microphone 4 and an error microphone 6 are embedded in the wall plane so that the mounting positions become the deepest surfaces 9. The area of the deepest surface 9 is almost the same as the area of a diaphragm of the reference microphone 4 and the error microphone 6. A second reference plane 10 which has an area larger than that of the deepest surface 9 is formed between the reference plane 8 and the deepest surface 9. Provided is a two-step concave structure 13 which includes a space from the reference plane 8 to the second reference plane 10 as a first concave space 11 and a space from the second reference plane 10 to the deepest surface 9 as a second concave space 12.</p> |
