Acoustic assessment of a novel visor concept with aerodynamic sealing for medical care

Abstract

This paper presents the experimental acoustic assessment and optimization of a novel solid visor with aerodynamic sealing for medical care. This Personal Protective Equipment (PPE) ensures an effective aerodynamic sealing of the breathing zone thus reducing the risk of inhaling droplets and aerosols carrying a potential infectious agent. The PPE relies on an air curtain system that may generate considerable noise unsuitable for prolonged usage, so it is essential to investigate solutions to reduce the noise level. The main investigated sound descriptors were the A-weighted Noise Equivalent Level, the Third-Octave Frequency Distribution, and the Speech Intelligibility Index (SII), considering different solutions for air flow rate, tube diameter, thickness and insulation, configurations of the tube splitter and plenum, and the incorporation of physical barriers and a sound muffler. Through several optimizations, noise equivalent levels were reduced by 20 to 30 dBA for air flow rates of 15 to 30 l/min. The final prototype generates a maximum noise level of 45.2 dBA. The SII was improved from poor to excellent, with values close to 1 for all air flow rates considered. The impact on the speech was investigated and the results were also compared to those obtained with a surgical mask and a FFP2 respirator. This study shows the potential of employing different strategies to enhance the acoustic performance of personalized air-curtain protective devices.