Some of the companies operating in the main and sub-industry act with the skillful apprentice relationship and ear-filling information in the selection of materials that require acoustic performance. From this point of view, it is generally accepted that materials with high density and thickness generally absorb sound better. However, other factors need to be considered in terms of acoustics. Only in this way can the desired sound absorption performances be achieved. If only the density and thickness increase of the materials is achieved, the surface impedance values ​​of the materials also increase.

In terms of acoustic performance, two important factors are important: sound absorption coefficient and sound transmission loss value. When designing and producing products that require acoustic performance, material selection and acoustic performance testing of the selected materials are therefore crucial.

The following describes the factors that must be considered when determining the acoustic performance of a material. The properties showing the acoustic performance of the materials used are:

• Porosity: This is the ratio of total pore volume to total absorption material.
• Flow resistivity: This value indicates how easily air flow can enter a porous structure and the resistance to which the material is exposed.
• Pore ​​tortuosity: This value indicates the complex path of air particles moving with the pressure created by sound waves.
• Viscous characteristic length: This value indicates the energy absorption caused by friction losses according to the shape of the pores.
• Thermal characteristic length: This value indicates the energy absorption caused by thermal losses according to the shape of the pores.
• Density.
• Young's modulus: This value indicates how much elastic deformation of the material under force.
• Poisson's ratio: This is the ratio of the deformation in the direction of stress to the deformation perpendicular to the stress. Briefly, this ratio shows how much the diameter of a material that is lengthened or shortened by an external force becomes smaller or larger.
• Loss factor: This is the structural damping loss ratio of the material. As the frequency increases, the structural damping values ​​decrease.

Among these factors, the most important factor showing the acoustic performance of the material is the porosity value.

In general, material properties are considered as fluid phase and solid phase. The fluid phase generally determines the behavior of the material against the fluid. The solid phase shows the structural properties of the material.

In material selection, it is generally accepted that a material with high sound absorption performance will be effective in loss of sound transmission. However, the opposite is true. The material with high sound absorption performance does not perform at all in sound transmission loss measurements. Therefore, other material should be selected for the sound transmission loss performance.

Test measurements in authorized laboratories are determined according to the needs of the sector and the test periods. The main tests performed on this subject are as follows:

• Impedance tube measurement method. In this context, sound absorption coefficient measurements and sound transmission loss value measurements are made.
• Reverberation chamber tests. These tests are conducted in accordance with international standards. Therefore it gives more reliable results.

Test and inspection institutions and laboratories assist in the selection of materials to be used in the manufacturing companies, determination of the test environment to be used in the project stages, supervision of the preparation of the tests and evaluation of the results.

The tests are based on the following standard prepared by the American Testing and Materials Organization (ASTM): ASTM C423 Reverberation chamber method and standard test method for sound absorption and sound absorption coefficients.

Our company performs acoustic tests of building products in detail with a strong technological infrastructure and employee staff.