Düşük frekans gürültüsü için yüksek ses yutumuna sahip bir akustik metamalzeme geliştirilmesi

Machinery noise is an important problem for human health, environment, and efficiency and longevity of machines. Besides that, the insulation of noise is a legal requirement; it is also of importance in buildings, vehicles, aerospace structures and pipeline systems for better comfort and quality conditions. Conventional passive noise insulations are limited in practical use, since the mass law dictating that the thickness of the insulation material must be comparable in size with the propagation wavelength which makes them inefficient. Recently an "acoustic metamaterial" concept has emerged and proved itself that it may break the mass law in a certain frequencies or frequency bands. Acoustic metamaterials (AMMs) are usually periodic sub-wavelength artificial structures exhibiting extraordinary material properties, such as negative effective mass density and effective bulk modulus. This thesis concerns with designing of AMMs for suppressing low frequency noise with providing higher absorption. For this purpose, several different kinds of AMMs are designed for acoustic transmission lines and for panel absorbers. Acoustic performance parameters such as sound transmission, reflection and absorption coefficients are obtained to exhibit performances of the designed materials. They are determined by transfer matrix method and finite element method for acoustic transmission lines. All analyses take visco-thermal effects into account and metamaterial properties are characterized based on effective medium theory. For panel absorber AMMs, acoustic performance parameters are experimentally determined by impedance tube measurements.