| 摘要 |
PURPOSE:To improve an SN ratio by mutually off-setting charges generating in a piezoelectric outer layer and a piezoelectric inner layer by each electrical connection and preventing the effect of acoustic waves to be exerted on the piezoelectric inner layer by a sound-insulating layer when a piezoelectric cable is bent by external pressure. CONSTITUTION:When a piezoelectric inner layer 2 and a piezoelectric outer layer 8 concentrically formed through a sound-insulating layer 5 are wired so that a positive pole for the piezoelectric inner layer 2 is connected to a negative pole for the piezoelectric outer layer 8 and a negative pole for the piezoelectric inner layer 2 to a positive pole for the piezoelectric outer layer 8, output signals are lead out of both poles for the piezoelectric outer layer 8 and a piezoelectric cable is bent by external pressure, charges generated in the piezoelectric inner layer 2 and the piezoelectric outer layer 8 are denied mutually by each electrical connection. Accordingly, outputs corresponding to acoustic waves generated only in the piezoelectric outer layer 8 can be extracted while an effect due to external stress such as waving is removed to the minimum possible, and the S/N ratio of the outputs can be improved remarkably. |
