In this study, the insertion loss of devulcanized waste rubber baffles were evaluated. Acoustic baffles are suitable to reduce noise from the devices or machines by interfering with their emitting sound waves. Knowledge of the acoustic properties of the material used is of significant importance in ensuring the effectiveness of the acoustic properties of the baffle. Basic properties include airborne sound insulation, which is usually determined during laboratory tests. Baffles consists of sound absorbing and sound insulating materials. In this study, plasterboards were used as sound insulating material and devulcanized waste rubber as sound absorbing material. During the devulcanization process, porous granules are obtained, which can be used as an acoustic material. In this study, two types of rubber granules were devulcanized by grinding method and one other type was chemically devulcanized. Three types of rubber granules were mixed together in increasing 25 % proportion steps and glued with patented polyurethane glue. A total of 15 different composition devulcanized waste rubber granule boards were made. Rubber boards were attached together with the plasterboards. Insertion loss of the different composite baffles was measured in semi-anechoic chamber in a purposefully designed stand in 1/3rd octave bands. The results showed that the insertion loss of the baffles was mostly dependent on the rubber granule board density. When the density of the rubber board increased, the insertion loss also increased. The 5–6 dB insertion loss difference was measured between the most and least dense rubber granule board baffles.

According to circular economy principles, the recycling and reuse of tyre rubber waste are among the most advanced and ecological waste disposal technologies. Each year, about 19 million tons of tyres are produced, and this number increases every year. One of the most innovative ways to recycle rubber waste is devulcanization. There are many methods of rubber devulcanization, but the most popular is chemical devulcanization. Also, pre-process treatment is important before devulcanization. In this article, devulcanized rubber granules were used for the preparation of rubber samples. Two of the samples were obtained via the grinding method and one via chemical devulcanization. In total, 15 different rubber samples were produced for experimental measurements. Multilayer constructions, with two solid layers of plasterboard on both sides (GKB (a standard gypsum board) and GKFI (an enhanced-strength and surface-hardness gypsum board)) and the porous acoustic material of the rubber sample inside, were produced. Measurements were made in an impedance tube and compared with the results of a transfer matrix method (TMM) analysis. The same trends of resonant frequencies were determined. According to the results, the resonant frequencies depended on the thickness of the material, since transmission loss (TL) values depended on the mass of the construction. According to the test results of transmission loss, constructions with 50 mm thick rubber samples had results that were, on average, 3 dB better than those of structures with 25 mm thick samples and 5 dB better than those of structures with 12 mm thick rubber samples. In addition, it was found that higher-density plasterboards (GKFI) increased the overall transmission loss value of the structure by 5 dB. The same trends were determined using the TMM method. The test results showed that multilayered constructions with devulcanized waste rubber had high transmission loss results and could be used for sound-insulating structures.

The excessive noise of machines and devices could be reduced with the use of acoustic enclosures. Additional requirement for enclosures: free air circulation through construction walls, which is important for device ventilation. The acoustic properties of the construction parts are essential to model their ability to reduce noise. The basic properties of airborne sound insulation of construction walls and absorption of used material should be experimentally tested. In this article, sound reduction modelling of acoustic enclosure with recycled materials covered walls was presented. Sound pressure level reduction of enclosure was modelled with Odeon software. A 3D model was created that includes the acoustic properties of the materials used. The enclosure walls consist of two different constructions. The side walls and roof were made from a single plasterboard covered with recycled rubber material. The back and front walls were constructed as louver construction, which plates were mounted with the ability to change the tilt angle which allows to create an air transparent construction. Acoustic properties of the materials used were tested in different ways. Sound absorption properties of 50 mm thick sample of recycled rubber and transmission loss parameters of used sound insulating walls were measured in the impedance tube. The results of the experimental test of the construction parts were included in the 3D model. The modelling results represented a decrease in sound pressure levels with an increasing distance from the enclosure on different sides. Four different enclosures with different tilt angle of louver plates (0°, 15°, 30°, 45°) were modelled. Results were presented in the 125–4000 Hz frequency range. According to the results, efficiency of enclosure sound reduction with 45° tilted plates could reach up to 12 dB.

According to circular economy principles, the recycling and reuse of waste tyre rubber is one of the most advanced and ecological waste disposal technologies. Each year about 19 million tons of tyres are produced, and this amount is increasing each year. One of the most innovative ways to recycle rubber waste is devulcanization. There are many methods of rubber devulcanization, but the most popular are grinding and chemical. In this article devulcanized rubber granules were used for the preparation of rubber samples. Two of them were obtained by the grinding method and one by chemical devulcanization. 15 different rubber samples were produced for the experimental measurements. Multilayer constructions with two solid layers of plasterboard on both sides (GKB and GKFI) and porous acoustic material of rubber sample inside were produced. Measurements were made in an impedance tube and compared with the results of TMM analysis. The same trends of resonant frequencies were determined. According to the results, the resonant frequencies depended on the thickness of the material, since transmission loss values depended on the mass of construction. According to the test results of transmission loss, constructions with 50mm thick rubber samples had on average 3dB better results than the structures with 25mm samples and 5dB better results than structures with 12 mm thick rubber samples. In addition, it was found that higher density plasterboards (GKFI) increased the overall transmission loss value of the structure by 5 dB. The same trends were determined by the TMM method. The test results showed that multi-layered constructions with devulcanized waste rubber had high transmission loss result and could be used for sound insulating structures.

In this study, the insertion loss of devulcanized waste rubber baffles was evaluated. Acoustic baffles are suitable for reducing noise from the devices or machines by interfering with their emitting sound waves. Knowledge of the acoustic properties of the material used is of significant importance in ensuring the effectiveness of the acoustic properties of the baffle. Basic properties include airborne sound insulation, which is usually determined during laboratory testing. Baffle consists of sound absorbing and sound insulating materials. In this study, plasterboards were used as sound insulating material and devulcanized waste rubber as sound absorbing material. Devulcanization targets mostly the scission of sulphur crosslinks. Devulcanization techniques that have been explored in rubber recycling include thermos-chemical, microbiological, ultrasonic microwave thermos-chemical devulcanization in a supercritical carbon dioxide medium (scCO₂). In this study, two types of rubber granules were devulcanized by grinding method and one other type was chemically devulcanized. Three types of rubber granules were mixed together in increasing 25 % proportion steps and glued with patented polyurethane glue. Total of 15 different composition devulcanized waste rubber granule boards were made. Rubber boards were attached together with the plasterboards. Insertion loss of the different composite baffles was measured in semi-anechoic chamber in a purposefully designed stand in 1/3rd-octave bands. The results showed that the insertion loss of the baffles depends mostly on the rubber granule board density. Increasing the density of the rubber board, insertion loss also increased. 5–6 dB insertion loss difference was measured between the most and the least dense rubber granule board baffles.