  The scattering of waves is a ubiquitous phenomenon in physics, yet there are
numerous scenarios, such as the pursuit of invisibility, where suppressing it
is of utmost importance. In comparison to prior methods which are restricted by
limited bandwidths, here we present a technique to suppress sound scattering
across an ultra-broad spectrum by utilizing illusion metamaterials. This
illusion metamaterial, consisting of subwavelength tunnels with precisely
crafted internal structures, has the ability to guide acoustic waves around the
obstacles and recreate the incoming wavefront on the exit surface.
Consequently, two ultra-broadband illusionary effects are produced:
disappearing space and time shift. Simultaneously, all signs of sound
scattering are removed across an exceptionally wide spectrum, ranging from the
quasistatic limit to an upper limit of the spectrum, as confirmed by full-wave
simulations and acoustic experiments. Our approach represents a major step
forward in the development of broadband functional metamaterials and holds the
potential to revolutionize various fields, including acoustic camouflage and
reverberation control.
