  Acoustic cloaking for the suppression of backscattering inside ducts is
proposed in the audible range where plane waves are curved around the object
using the surface modes of the liner. It is numerically shown that a slowly
varying resonant liner (e. g. based on an array of tubes) creates a zone of
silence in which an object of arbitrary shape can be acoustically hidden for a
wide range of frequencies. And then, a resonant liner has deflecting properties
without reflection of the wavefront, which are close to an ideal invisibility
cloak. This kind of cloaking is effective in a wide frequency band and the
cloaking band is a function of the impedance and height of the obstacle
relative to the conduit. For smooth shaped obstacles, there is an ability of
the object to help hide itself, which increases the cloaking frequency band
(self-cloaking). Dispersion effects lead to slow sounds and distortion of the
wave phase.
