The relationship between floor vibration from an underground source and the airborne sound pressure level in the room

Abstract

ABSTRACTPrediction, measurement, and assessment of groundborne noise in buildings due to the operation of underground railways frequently involves knowledge of floor vibration and requires a calculation to be made to estimate the airborne sound pressure level that will be caused by the floor vibration. A rule-of-thumb conversion between the vertical velocity level and the airborne sound level is frequently made. Approximations using calculations of radiation efficiency of the floor plate and the room reverberation time are also sometimes made. This article reviews the classical equations for coupling between finite plates and rectangular rooms using wave acoustics, and their application to floor plates in buildings at low frequencies. It also compares calculated relationships between floor velocity and the room sound pressure level with numerically modelled sound pressure in the airspace above a vibrating plate. Conclusions are drawn regarding appropriate ways of assessing airborne noise caused by a vibrating floor plate when only the floor vibration is known.