Investigation of Optimal Installation Positions for Two Coherent Motors to Minimize Structure-Borne Sound Transmission to a Floor in Buildings

This paper investigates the optimal installation positions of two coherent motors by analyzing the structure-borne sound power transmission to a simply supported rectangular concrete floor. The free velocity and source mobility of the motors were measured experimentally, while the receiver mobility of the floor was obtained via the modal summation method. Based on these parameters, the study examined how installation positions and inter-point interactions influence the transmitted sound power. The results showed that the difference in structure-borne sound power level between the optimal and worst-case installations was 20.44 dB in the 1/3-octave band centered at 50 Hz. Crucially, the optimal positions remained unchanged even when inter-point interactions were neglected in the power calculations, providing actionable guidance for practical vibration isolation design in building applications.