According to the Waste Management Policy of the European Union, the recycling and reuse of various wastes is considered the most ecological and advanced waste disposal technology with the lowest impact on the environment. By applying circular economy principles, plastic waste will extend its life cycle and be used as secondary raw materials to create structures with good sound insulation and absorption properties. Structures created from metamaterial with plastic were studied for their sound-absorbing properties in an impedance tube. A combined 100 mm long resonator design with a 2.0 mm perforation, 20 mm thick plate, regardless of whether it is an “X”- or “O”-shaped resonator, achieved a good sound absorption peak at 315 Hz of 0.94. When the combined structures of 50 mm long “X”- and “O”-shaped designs were compared, different sound absorption peaks at high frequencies were achieved. A slightly better sound absorption peak of 0.95 was achieved at 500 Hz with the “O”-shaped resonator and 0.93 at 630 Hz with the “X”-shaped resonator. The results show that the combined plastic and rubber structures can be integrated into building structures and be used as an alternative to improve building acoustics and reduce noise and reverberation.

This study investigates the development and acoustic performance of a layered composite structure composed of plastic microfibre pulp (PMFP) and plastic acoustic metamaterial (PAM), designed for low-frequency sound wave control. Addressing the dual challenge of reducing plastic waste and enhancing low-frequency sound absorption, the research explores the use of recycled plastic materials in innovative acoustic applications. PMFP was tested in various thicknesses, while PAM resonators were 3D-printed with adjustable neck lengths and diameters to achieve optimal sound absorption characteristics. The acoustic performance of the composite materials was evaluated in an impedance tube according to ISO 10534-2 for their sound-absorbing properties. Results showed that with increasing thickness of the PMFP sound, absorption peaks shifted to the lower frequencies, with 50 mm thick samples exhibiting a peak absorption coefficient of 0.74 at 500 Hz. When combined with PAM, the structure’s effectiveness increased significantly, with the best-performing configuration (PAM with a 4.5 mm neck diameter and 3.0 mm neck length) achieving a highest absorption coefficient of 0.93 at 1250 Hz. Moreover, introducing air gaps behind the composite material further enhanced low-frequency absorption, with a 50 mm air gap shifting the peak sound absorption to 315 Hz, reaching a coefficient of 0.87. The study concludes that the layered composite structure, with recycled plastic waste, provides an effective and environmentally sustainable solution for low-frequency sound absorption. This makes it suitable for use in various industrial and environmental noise control applications, offering an innovative approach to control noise in indoor areas while addressing plastic waste concerns.

Noise pollution has become an increasingly discussed environmental problem in recent years. Developing a traffic infrastructure and recent sustainability goals require new solutions to mitigate noise pollution. This paper investigates the efficiency of the noise barrier made entirely of recycled materials. This solution would help achieve the United Nations sustainable development goals (SDGs). The proposed barrier target SDGs are: Good Health and Well-being (SDG 3); Industry, Innovation, and Infrastructure (SDG 9); Sustainable Cities and Communities (SDG 11); Climate Action (SDG 13). The changed barrier parameters were the parameters of the perforated panel and the air gap behind the porous material. To solve the optimisation problem, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method was used. The results showed that the proposed barrier configuration was the following: perforation shape—round, perforation diameter—5 mm, increment angle perforation—30°, thickness of the perforated panel—10 mm, porous absorbing material (composite rubber granule and hemp shive panel (RGHS))—50 mm thick, 20% of hemp shive content, air gap between absorbing material and the rigid backing—100 mm. The total thickness of the noise barrier was 180 mm. The acoustic parameters of the noise barrier structure were: α_avg. = 0.24, peaking at 0.51 (1250 Hz) and R_W = 39.7 ± 1.0 dB. These results indicate that the proposed barrier made of recycled materials could be a sustainable alternative for noise pollution mitigation and improving people’s quality of life.

Noise – messy loud noises of different frequencies, which have various types of pressure, which can be felt as air vibrations or sounds that interfere with human comfort. This kind of noise can be transferred through building construction and/or directly to the human ear. To prevent or minimise noise transfer, sound insulation of considerate construction should be improved. The accumulation of plastic waste and the lack of proper disposal methods has created a critical and unprecedented problem where plastic waste enters our water resources, overflows landfills, leaches into the soil, and enters the air, polluting all natural objects and other resources in our environment. In this research, plastics would be used as secondary raw material to create a better sound insulation solution than what is currently available on the market, such as plasterboard. By applying Circular Economy principles, plastic waste will extend its life cycle and be used as secondary raw material to create metamaterial structures with good sound insulation properties. Numerical validation of metamaterial acoustic characteristics will be compared to the experimental study using an impedance tube.

According to the Waste Management Policy of the European Union, the recycling and reuse of various wastes is considered the most environmentally friendly and advanced waste disposal technology that has the least impact on the environment. By applying the principles of the Circular Economy, plastic waste will extend its life cycle and will be used as secondary materials to create metamaterial structures with improved sound absorption and insulation properties. The aim of this study was to determine plastic potential for use in acoustic structures. Acoustic metamaterial resonators, created from plastic, were measured in an impedance tube according to standards ISO 10534-2 for their sound absorbing and ASTM E2611 for their insulating properties. Two types of plastic, PLA and recycled PET-G, were used in acoustic metamaterial 3D printing process. For sound insulation, combined resonator systems were used to control symmetrical wall sound resonance. Sound absorption of both PLA and PET-G metamaterials were peaking at 1600 Hz with 0.93 and 0.89 sound absorption coefficient, respectfully. The results showed that combined constructions with plastic metamaterials can be integrated into building structures and used as an alternative for improving building acoustics, reducing indoor noise and reverberation time.