Acoustic metamaterials and phononic crystals represent a promising platform
for the development of noise-insulating systems characterized by a low weight
and small thickness. Nevertheless, the operational spectral range of these
structures is usually quite narrow, limiting their application as substitutions
of conventional noise-insulating systems. In this work, the problem is tackled
by demonstration of several ways for the improvement of noise-insulating
properties of the periodic structures based on coupled Helmholtz resonators. It
is shown that tuning of local coupling between the resonators leads to the
formation of ultra-broad stop-bands in the transmission spectra. This property
is linked to band structures of the equivalent infinitely periodic systems and
is discussed in terms of band-gap engineering. The local coupling strength is
varied via several means, including introduction of the so-called chirped
structures and lossy resonators with porous inserts. The stop-band engineering
procedure is supported by genetic algorithm optimization and the numerical
calculations are verified by experimental measurements