Abstract: An arrangement for ultrasonically measuring the elastic properties of a moving web includes an ultrasonic wave generator and at least two ultrasonic wave detection devices which receive the generated ultrasonic wave without contacting the web. The received signal is processed such that the desired properties if the moving web can be determined.

Abstract: 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 device in the web at an excitation point. A reference ultrasonic wave reradiated into the air from the excitation point is indicated. A pick-up device is provided for receiving ultrasonic sound reradiated from the paper web at a predetermined distance form the location of the sound generating device. The ultrasonic sound generating device and the reference ultrasonic receiving device are provided on the same side of the paper web. At least one of these two kinds of devices includes a number of elements provided symmetrically in relation to the other device.