Aerodynamic noise within hyperbaric chambers: assessment and possible mitigation

The use of hyperbaric chambers prevailed in medical therapy for vascular diseases and for outbreaks of embolism in emergency situations. This implies the achievement of environmental pressure conditions from two to three times higher than the atmospheric one, in such a short time to require delivery of the air flow that leads to very high intensity noise. The attenuation of this noise is usually performed through the installation of silencers at the air outlets. In this work a series of noise measurements is presented, carried out inside the chamber, limited to the periods it is available to maintenance activities, in various conditions of the opening of the air inlet valve, with and without silencers mounted on the air outlet nozzles and with or without different layers of floor covering. In order to characterize the attenuation capacity of the silencers and to verify that the air flow is the most significant source of noise, a series of noise measurements is also presented, carried out in the open field while emptying a pressurized tank, in various conditions of opening of the exhaust valve, for different types of silencers placed at the outlet. The analysis of the frequency spectra allows to evaluate the behaviour of these devices, at the light of theoretical predictions concerning the aerodynamic noise. The results suggest that the optimization of some of the flow parameters and the operating conditions of the chamber can contribute significantly to the reduction of noise, with a consequent net improvement of such device, in particular under operating conditions of emergency.