Recycled paper fibres as sound absorbing material

Abstract

Noise pollution is a workplace hazard which causes loss of hearing, depending on the sound pressure level and duration of exposure. Because duration of exposure is usually uncontrollable, sound absorbers are used to reduce the value of sound pressure level. A common method to reduce noise is to use porous sound absorbers made out of mineral wools or glass fibres. However, these materials pose health risks and are non-recyclable. This project aimed to fabricate a sound absorber using recycled paper which is in the form of egg cartons as an alternative to the abovementioned fibres. Paper fibres possess high fibre porosity and can be manufactured in a manner which the properties can be easily controlled, making them ideal to be made into sound absorbers. Furthermore, they are biodegradable, do not pose health risks and can be manufactured into different shapes easily. Recycled paper was first turned into pulp, blended and poured into moulds. Different amounts of pulp were compressed until the sample size was approximately 20 mm thick and then dried in a furnace dryer at 60??C for 12 hours. The samples were tested using a two-microphone, transfer function impedance tubes according to the ISO 10534-2 standard. Its porosity was determined using a modified wash basin method. The results indicate that the optimum panel has an average noise reduction coefficient, (NRC) of 0.50, which qualifies it to be used as a sound absorbing material. It also encounters its maximum value of 0.98 which occurred at the 1575-1675 Hz range. When compared to other materials, recycled paper has similar properties as coir fibre and is quite comparable to other commercial sound absorbers at the same thickness.