  We investigate the sound propagation in an air-filled tube periodically
loaded with Helmholtz resonators. By tuning the Helmholtz with the Bragg
resonance, we study the efficiency of slow sound propagation in the presence of
the intrinsic viscothermal losses of the system. While in the lossless case the
overlapping of the resonances results in slow sound induced transparency of a
narrow frequency band surrounded by a strong and broadband gap, the inclusion
of the unavoidable losses imposes limits to the slowdown factor and the maximum
transmission. Experiments, theory and finite element simulations have been used
for the characterization of acoustic wave propagation. Experiments, in good
agreement with the lossy theory, reveal the possibility of slowing sound at low
frequencies by 20 times. A trade-off among the relevant parameters (delay time,
maximum transmission, bandwidth) as a function of the tuning between Bragg and
Helmholtz resonance frequency is also presented.
