Identification of Structure-Borne Sound Paths of Service Equipment in Buildings Using Structural-Acoustic Reciprocity

Low-frequency noise from service equipment in buildings tends to be of a structure-borne naturerather than an airborne nature. The transmission between different building elements canbe determined on a power basis. The injected structure-borne sound power by an installationcan be determined by multiplying velocities and contact forces in each of the installation’scontact points. The velocity can be measured approximately by use of accelerometers closeto the contact points, but the measurement of the force is less obvious. Force sensors shouldbe inserted between the installation and the building element, which is often difficult or evenimpossible. Even when it’s not that tedious, it is advisable not to alter the path of soundtransmission, since small changes can imply large differences in injected structure-bornesound power. In this paper, contact forces of a fitness vibration plate are estimated through astructural-acoustic reciprocal method. First, the installation in a source room is put into operationand sound pressures in a receiver room are measured at multiple receiver points. Next,a dedicated volume sound source is placed in the receiver points in order to determine thetransfer functions of the sound source’s volume acceleration to the acceleration of the buildingelement at the position of the contact points. A dedicated volume sound source was usedthat approximates point source behaviour and produces a high noise level down to very lowfrequencies (> 20 Hz). This enables accurate measurement of the structure-borne soundtransmission. And, in a second step, it allows inverse estimation of the structural-acousticcontact forces down to these low frequencies. The estimated forces are compared with directlymeasured forces.

ISBN:9781615677368

Jaar van publicatie:2009