Valorization of some waste to obtain sound-absorption composite materials, targeting the reduction of the noise pollution

The noise is a complex of sounds without a periodical character that affect the biological and psychological health of humans and other organism from nature. Noise pollution represents the human or animal exposure to sounds at disturbing, stressful or harmful levels. This paper aims to introduce new systems for absorption and attenuation of noise from industry or from urban and extra-urban transport based on composite materials made from recycled solid waste. Compared to conventional materials this new type of composites incorporates various wastes that can harm the environment. The absorption coefficient is used to express the capacity of a material to absorb the sound waves – to transform the kinetic energy of the sound waves into thermal energy. It is expressed in percents and represents the proportion between the total sum of energy that is transmitted and absorbed by the material and the total incidence energy of sound waves. This paper presents several types of composites produced using waste matrix binder. Absorbing capacity of sound for the new composites varies depending on the proportion of waste used. Also, are presented correlations between the grading of the reinforcing material that is used, the density and porosity of the resulted composite and the absorption sound waves coefficient for composite material samples which are reinforced with different wastes.