TY - JOUR A1 - Höller, Christoph A1 - Gibbs, Barry M. T1 - Indirect determination of the mobility of structure-borne sound sources JF - Journal of Sound and Vibration N2 - Methods are considered for the indirect determination of the mobility of structure-borne sound sources. Instead of performing measurements on the source in the free state, the source mobility is obtained from measurements made in-situ. This approach is beneficial if the source is difficult to suspend, or if it contains nonlinear structural elements. Two formulations for an indirect source mobility are derived theoretically. The first requires measurement of velocities at or near to the contact points. The second involves measurement of remote velocities only. Neither of the methods requires excitation at the contacts in the coupled state. Numerical simulations of coupled beams are used to validate the two methods and investigate their accuracy and reliability with respect to typical measurement errors, such as background noise and inaccuracies in sensor positioning. It is found that these can have a significant effect on the methods considered. Several experimental case studies with single-contact and multi-contact sources are performed. The results confirm the validity of the two methods in principle, but highlight their sensitivity to experimental errors. In a representative case study with a fan unit, average errors range between ±5 dB and ±10 dB, with occasional errors of up to 30 dB. Y1 - 2015 U6 - https://doi.org/10.1016/j.jsv.2015.01.011 VL - 344 SP - 38 EP - 58 PB - Elsevier ER - TY - JOUR A1 - Höller, Christoph A1 - Gibbs, Barry M. T1 - Inverse Method to Obtain Blocked Forces of Vibrating Sound Sources in Buildings JF - Acta Acustica united with Acustica N2 - 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. Y1 - 2017 U6 - https://doi.org/10.3813/AAA.919092 VL - 103 IS - 4 SP - 639 EP - 649 PB - ingenta ER -