Acoustical comfort

In the available sources, only few research attempts were encountered that dealt with the acoustics of tensile membrane structures and none of them was about the emergency cases. However, the below presented research cases have some common parameters and help to understand the general principles and approaches for acoustical assessment in this kind of structures. 
ETFE is one of the ubiquitous materials in tensile membrane structures. Although it is not so commonly used in an emergency because of the price the analysis \citep*{Toyoda2013} done by Japanese researchers on reducing the rain noise on ETFE membranes gives clues on understanding the problem and proposes solutions that may be applied for other materials as well such as PVC membranes. The researchers designed several theoretical solutions (adding double air chamber, gel sheet, non-woven fabric) to the raindrop drumming problem and then applied laboratory tests to determine their effect on noise reduction. Despite some discrepancies, the tests showed that by adding some damping materials the inner acoustical comfort may be fostered. 
In 2014 researchers from the University of Catania published an article \citep{Patania2014} in The 21st International Congress on Sound and Vibration. Here the goal was to investigate a case of a study room covered by a textile structure in order to improve its acoustical characteristics. The problem here is that as usually it happens the tensile membrane structures may have high ceilings due to the structural properties. These high ceilings create dead volumes that extend the wave travelling to the unoccupied distant spaces that will afterwards in laggard reflection cause inconveniences. The room was examined with sensors and later with the corresponding simulation was carried out to optimize the solutions. The researchers made clear that for a better outcome of the design in acoustical terms the corresponding simulations and optimizations should be carried out.
One of the very few research attempts done to deal with the acoustics inside the textile tent structures is the Analysis of the Acoustic Conditions in a Tent Structures \citep{Urb_n_2015} by Slovakian researchers (2015).They pinpoint out one of the main differences of acoustical behaviour of textiles structure which is that in these structures usually, you have more reflection of high-frequency waves as opposed to the higher reflection of low-frequency waves which exists in conventional quasi-flat structures. The research is about a case study of a big tent dedicated to cultural activities and therefore is only partially corresponding to the problems of this research. The tent performance was measured in situ and later simulated for comparison. As a result of the analysis, it was shown that curtains can be inside the tent to improve acoustical characteristics but nevertheless for better sound propagation in big tents some audio equipment may be required for cultural events. Although this doesn’t relate to the given topic much, from the analysis it’s beneficial to know that simulation techniques may be applied to tent-like structures to determine acoustical environment for the emergency tents as well.