Acuña, EI & Dobson, A 2017, 'Results of the return air raise silencer system upgrade at Totten Mine', in M Hudyma & Y Potvin (eds), UMT 2017: Proceedings of the First International Conference on Underground Mining Technology, Australian Centre for Geomechanics, Perth, pp. 97-102, https://doi.org/10.36487/ACG_rep/1710_07_Acuna (https://papers.acg.uwa.edu.au/p/1710_07_Acuna/) Abstract: The Totten Mine project specified two parallel main return air fans locatedon-surface equipped with baffle silencers designed to attenuate the sound levels from the fan outlets. In late 2014, an acoustical study determined that the return air fans were responsible for a series of noise disturbances in a community situated approximately 9 km to the northeast. The results of the acoustical study also indicated that the silencers were significantly underperforming due to clogging with a combination of particulate and moisture drawn from the underground mine. During 2015 and the beginning of 2016, Totten Mine implemented a cleaning procedure to mitigate the underperformance of the silencers. Unfortunately, noise monitoring of the cleaning procedures indicated diminishing results over time. As a result, a temporary solution was identified and implemented in Q3 and Q4 of 2016 to allow adequate time for engineering and defining of a long-term solution. The proposed temporary solution, however, had the potential to become the permanent solution, subject to an evaluation of performance. This paper presents the results of the temporary solution evaluation, when compared to the baseline cleaning procedure. The temporary solution is then compared to the proposed alternatives that were to be part of a feasibility study for both capital (CAPEX) and operational (OPEX) cost evaluation. The resulting long-term solution to manage noise issues on mine return air systems, similar to the Totten experience, is also presented and discussed. Keywords: main return air raise fans, silencers, noise level measurements