Inverse Method to Obtain Blocked Forces of Vibrating Sound Sources in Buildings

Vibrating sources, such as building service equipment, are major contributors to noise in buildings. In order to predict and subsequently reduce the sound pressure levels generated by these devices, it is necessary to first predict the total vibrational power injected by them into the supporting building structure. Whilst simplified methods are available for the calculation of the total power through all contacts, it would be beneficial to have more detailed knowledge of the dominant contact powers. For sources on low-mobility building elements, the contact powers are determined by the blocked force, along with the real part of the receiver mobility at each contact. This paper describes a novel inverse method to obtain the blocked forces at each contact. The method employs an instrumented reception plate, which is numerically modelled to allow optimum accelerometer positions to be selected, for any source and any location. The underlying theory and measurement procedure are described, and experimental validations are presented.