The structural-acoustic reciprocal method to determine forces between service equipment and
a building element has been applied on an operating vibration plate generating vertical lowfrequency
vibrations into a concrete floor in a laboratory environment. The method is based on the
transfer function of the volume acceleration of a dedicated volume source at a receiving point in the
building over the acceleration of the building element at the contact points of the installation. The
volume source is designed to send out low-frequency waves as a point source, down to 20 Hz. The
method yields satisfying results as a good agreement was found between the direct measurement
and the inverse technique. The method is preferred above use of the transfer function of force over
pressure when the contact point is difficult to reach and when the surface of the building element is
brittle.
Still, the method has to be