| 摘要 |
<p>The invention relates to a system for measuring ultrasonically the elastic properties of a moving paper web. A noise type ultrasonic sound wave is generated by an ultrasonic sound generating means (4) in the web at an excitation point. A reference ultrasonic wave reradiated into the air from the excitation point is indicated. Pick-up means (M2; Mic2A, Mic2B; Mic3A, Mic3B) is provided for receiving ultrasonic sound reradiated from the paper web at a predetermined distance from the location of the sound generating means (4). The ultrasonic sound generating means (4) and the reference ultrasonic receiving means (M1,5) are provided on the same side of the paper web. At least one of these two kind of means comprises a number of elements provided symmetrically in relation to the other means.</p> |
