Motivating engineering students on using circular economy for the development of low-cost acoustic materials.

Abstract

This paper presents a recent experience of working with intermediate-advanced students of Civil Engineering, who converge in a curricular Workshop on Environmental Engineering. The topic to be worked on during the workshop was to improve the acoustic quality of a multipurpose space that is very popular among students for group studying, and near which there is a lightly built office block, distributed over five floors. The high noise levels in this place not only negatively affect the use of time by the students, but also that of the teachers who work in that office block. By proposing this topic for the 2021 academic course, the students already had a clear experience of the proposed case study, despite the fact that due to the health emergency that the world has been experiencing for more than a year, there have been neither face-to-face classes nor authorization for massive use of study places. In addition, some of the students had taken subjects that brought them closer to the basic concepts of acoustics and integral solid waste management. The multipurpose space is equipped with mobile panels (with small wheels) that have, on both sides, an upper part intended for a whiteboard and the other covered with felt. A first approach was made to the possibilities of modifying the design of the panels to incorporate a head -in the style of those used in acoustic screens-, rather parabolic in shape and with its lower face protected with a sound-absorbing material. In a second instance, possible suitable materials were analyzed to be used in that face of the head and in the lower part of the mobile panels. At the very beginning, the wide variety of options ranging from living plant absorbents to sophisticated commercial materials. However, by conducting a quick cost analysis, the students suggested the possibility of developing their own materials from waste. The idea arose from a set of panels developed some years ago by a Design student in her graduation thesis. She created low-cost panels from wool waste generated by the weavers of Manos del Uruguay, a national company of high-quality handmade products. Those panels achieved good acoustic performance and were tested to confirm that they were fireproof. In the current case, the identification of common urban solid waste was prioritized, preferably that generated at home or at the Faculty, to potentially be used as raw material to obtain acoustic absorbent materials. Among the options that were considered, non-directly recyclable paper (for example, due to its coating) and the results of document shredders were found to be the most abundant; the first ones are usually generated at home and the others, in the Faculty offices. When working with paper waste, the goal is to create lightweight, airy panels with rough or textured surfaces. A second option was to deepen the work with textile waste materials; in this case, the possible difficulty would be to access the waste. The work of the students involved the next steps: diagnosing the current situation; designing the solution; making some samples of the acoustic panels made by paper wastes, in order to test their acoustic properties; calculating their acoustic absorption coefficients; proposing the solution to be implemented, its cost and the time for putting it into practice. The students based their option by trying waste-based materials on the need to reduce the amount of wastes, knowing that they would not solve the problem but they “lead by example”. They achieved a very good acoustic response of the panels, so they suggested to the Faculty authorities to use these kind of panels, placed into canvas containers; these bags or containers improve the acoustic absorption performance of the panels and allow to wash the bags. However, it is possible that the final decision of the institutional authorities will not be in favour of using hand-made recycled panels as part of the furnishings for the multipurpose space.