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Appl. Sci. 2017, 7(11), 1121; https://doi.org/10.3390/app7111121

Low-Frequency Noise Reduction by Earmuffs with Coir and Coir/Carbon Fibre-Reinforced Polypropylene Ear Cups

1
Kinetics Design and Manufacturing, Singapore Technologies Kinetics Ltd, 249 Jalan Boon Lay, Singapore 619523, Singapore
2
Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
3
Singapore Institute of Manufacturing Technology (SIMTech), Agency for Science, Technology and Research (A*STAR), 73 Nanyang Drive, Singapore 637662, Singapore
*
Authors to whom correspondence should be addressed.
Received: 15 September 2017 / Revised: 25 October 2017 / Accepted: 27 October 2017 / Published: 31 October 2017
(This article belongs to the Section Acoustics and Vibrations)
Full-Text   |   PDF [3333 KB, uploaded 31 October 2017]   |  

Abstract

Natural fibres have been extensively studied due to their potential in a wide range of applications. This study aims to demonstrate the viability of composite earmuffs for low-frequency noise reduction in continuous and transient noise environments. Pink noise and aircraft take-off exterior noise were considered for the former and the latter, respectively. The assembly components of the composite earmuffs were kept identical to a commercial earmuff, which served as a reference for results comparison. Based on the profile of the ear cups from the commercial earmuff, composite ear cups were fabricated from coir fibre and coir/carbon fibre fabrics reinforced with polypropylene. In contrast to the commercial earmuff, the composite earmuffs showed improvements in insertion loss at specific frequencies in the respective noise environments. In pink noise, up to 12 dB improvement in insertion loss was achieved. In aircraft take-off exterior noise, up to 8.6 dB improvement in insertion loss was achieved at 160–544 Hz particularly by the coir fibre-reinforced polypropylene earmuff. Consequently, the proposed earmuffs may find applications in areas where noise exposure is predominantly low-frequency—in some vehicle cabins, at airports, and at construction sites, for example. View Full-Text
Keywords: low-frequency noise; noise reduction; hearing protection; earmuffs; natural fibre; occupational noise low-frequency noise; noise reduction; hearing protection; earmuffs; natural fibre; occupational noise
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Ang, L.Y.L.; Tran, L.Q.N.; Phillips, S.; Koh, Y.K.; Lee, H.P. Low-Frequency Noise Reduction by Earmuffs with Coir and Coir/Carbon Fibre-Reinforced Polypropylene Ear Cups. Appl. Sci. 2017, 7, 1121.

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