| 摘要 |
PURPOSE:To reduce reverberation and to improve detecting precision by arranging a mask body which is provided with a slit opposite an ultrasonic oscillator, and using an elastic body for the internal surface part of the mask body at the ultrasonic oscillator side. CONSTITUTION:The ultrasonic acoustic mask 3 is arranged opposite the ultrasonic oscillator B, and the internal surface parts of a cylinder part 1 and the mask body 3A are made entirely of an elastic body 12 such as silicone rubber. Further, an annular elastic plate part 12a is provided to the end part of the elastic body 12 in one body and brought into contact with the external surface of a terminal plate 7 to absorb the signal of ultrasonic pulses, thereby suppressing the excitation of the acoustic mask 3. Consequently, the ultrasonic pulse signal is acquired by the oscillator B securely to improve the detecting precision, and the simple constitution is obtained advantageously without any increase in cost.
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