Abstract: A device for treating a web of fibrous material, the device comprising: a sensor for detecting vibrations; a multi-part housing including a cover; and a plurality of fiber treatment tools arranged inside the multi-part housing, the plurality of fiber treatment tools including a plurality of treatment profiles facing one another, being arranged spaced apart from each other so as to form at least one treatment gap with the plurality of treatment profiles, and being mounted rotatably relative to one another, at least one of the plurality of fiber treatment tools being mounted axially movable in the multi-part housing so as to be configured for adjusting a width of the at least one treatment gap between the plurality of treatment profiles facing each other, at least one of the plurality of fiber treatment tools being supported by a part of the multi-part housing, the sensor being arranged on the multi-part housing.