**5. Conclusion**

*Waste in Textile and Leather Sectors*

**98**

**Figure 7.**

**Figure 6.**

*Sound absorption coefficients based on the impedance tube method.*

*Sound absorption coefficients based on alpha cabinet method.*

Materials can be tested at a wide frequency band in case of their sound absorption properties. In this study, the tested frequency range is 400–10,000 Hz. According to **Figure 7**, between 400 and 1600 Hz, sound absorption coefficients of all nonwoven

Along with the growing population, noise has become one of the major problems of everyday life, affecting our quality of lives and, in some cases, our health. As the studies on reducing the noise generation continue, new solutions are being searched on systems that allow absorbing more quantities of the present disturbing noise. Within this scope, many different technical textile materials are produced, which are closely related to building construction, automotive, and machinery industries. The use of these high-performance products is becoming increasingly widespread in terms of technical specifications. However, in today's competitive conditions, products that can compete in terms of cost are more preferred in the market. Recycled surfaces are one of these preferred products. In addition to the price advantage, waste materials are transformed into usable products by recycling, which is completely an environmentally friendly production that provides sustainability.

In this study, characteristics of conventional polyester and polypropylene nonwoven insulation materials commonly used in the market and the nonwoven fabrics produced from recycled materials were compared. When the test results were examined, it was concluded that the recycled materials used in sound insulation area had very successful competitive performance when compared with the conventional materials. They had the qualifications supplying the expectations in terms of sound insulation when produced in enough thickness value.

Insulation materials are used, especially in areas where sound insulation is desired (e.g., children's houses, hospitals, entertainment places, and automotive sector) and in civil engineering area. In addition, it is a good application area for recycled materials to supply a sustainable world, to increase the environment friendly approach, and to evaluate the waste materials in a technical field. By the year 2019, price of PP fiber in the market is about 3.2 \$/kg, 1.6 \$/kg for r-PP fiber, about 1.6 \$/kg for 100% PES and r-PET fibers, and 1.2 \$/kg for rm-PES fibers. In the scope of economy, it can be foreseen that recycling materials will provide an important advantage for both producers and consumers.
