Effects of isolating machine vibrations on the transmission of structure-borne and air-borne sound energy

A large proportion of noise in industrial plants is generated by the vibration of rigid structures such as buildings and machines. Well-designed vibration isolation of vibrating sources can effectively reduce the transmission of energy into supporting and surrounding structures. The presented paper investigates the conditions for reducing the transmission of structure-borne sound from vibration sources, such as from industrial machines, through building structures of an industrial hall and into the mounting base of surrounding machines. The solution of this problem is based on the theoretical knowledge and methodology of the transmission of longitudinal and transverse waves and measurement of structures involved. Measurements of vibration at the sources and along the path of transmission, as well as sound measurements in the working place, were performed. The results of the vibration measurements were compared at different configurations of the mounting base as well as the application of specific vibro-acoustic source with respect to the blocking forces and wave transmission, in order to determine their effects on the mounting base of the machine and transmission of energy to its surroundings. Measurements were performed for different mounting bases and vibro-isolators to compare real results with theory. Mechanical vibration and sound were measured and FFT analysis was used to detect vibro-sound energy. In the first case, low-frequency vibration is analysed in the mounting base and the transmission of structurally-borne waves are investigated. Finally, the paper suggests some measures which can reduce unwanted vibro-sound energy acting on the machines, buildings and technological structures of the working environment.