MY THUMB IS ON THE BICYCLE PUMP-CONSIDERATIONS FOR THE VENTING OF AIR CAVITIES BELOW STRUCTURALLY ISOLATED FLOATING FLOORS

Performance spaces and fitness developments are commonly designed with floating floors to attenuate the low frequency sound fields which their activities generate. Whilst the natural frequency of the primary structure, floating element and isolation bearings are of critical importance, it is possible that the air trapped below the floating floor can become stiffened by the deflection of the floor, reducing the insertion loss of the system. This paper summarises the issue and proposes a process by which the impact of this phenomenon can be assessed, which involves calculating whether there is sufficient time for stiffening effects to occur, assessing whether connected volumes can accommodate air movement, and using volume flowrate to size a “vent opening” in the system if previous steps suggest this is necessary. It is noted that providing a precise analytical model of the behaviour of semi-pressurised air below a slab is complex and requires a number of assumptions. As such this paper attempts to provide a conceptual framework to consider the physics of the phenomenon and to strengthen the judgements that engineers must make regarding venting the cavity.