Publica
Hier finden Sie wissenschaftliche Publikationen aus den FraunhoferInstituten. Sound transmission loss of onedimensional systems containing fictitious metamaterials
 Seeber, B. ; Deutsche Gesellschaft für Akustik DEGA, Berlin: Fortschritte der Akustik. DAGA 2018 : 44. Jahrestagung für Akustik, 19.22. März 2018, München Berlin: DEGA, 2018 ISBN: 9783939296133 ISBN: 3939296139 pp.7578 
 Deutsche Jahrestagung für Akustik (DAGA) <44, 2018, München> 

 English 
 Conference Paper 
 Fraunhofer IBP () 
Abstract
Metamaterials are distinguished from ”normal” materials by unusual properties. Some behave as if the mass density or some elastic modulus were negative. However, in ”real metamaterials” such unusual properties appear in limited frequency ranges only. Moreover, these properties are as a rule complexvalued, i.e. implicate damping, and depend on frequency. By contrast, the properties of ”fictitious metamaterials” may be defined arbitrarily, regardless of physical realizations. Analytical studies of simple cases with frequencyindependent negative mass densities and elastic moduli lead  via the transfermatrix method  to instructive findings. The sound transmission loss of a massspringmass system is optimal, if the spring constant is positive and both masses are equal and negative, or if the spring constant is negative and both masses are equal and positive. The transmission loss of a homogeneous onedimensional elastic layer, which may be regarded as a generalization of a rigid mass or a massless spring, shows similar symmetries. With respect to the signs of the elastic modulus and the mass density the transmission loss depends only on the product of the two signs, i.e. on whether the signs are equal or different. Corresponding results are obtained for an elastic layer sandwiched between two rigid masses.