Linear acoustic metamaterials (LAMs)are widely used to manipulate sound, but it is challenging to obtain bandgaps withthe generalized width (the ratio of the bandgap width to its start frequency) γ>1 based on linear mechanisms.Here, we adopt both theoretical and experimental approaches todescribe the nonlinear chaotic mechanism in both one-dimensional (1D) and two-dimensional (2D)nonlinear acoustic metamaterials (NAMs). This mechanismenables the strongly NAMsto reduce the transmission of wave by as much as 20-40dB in an ultra-low and ultra-broad bandthat consists of bandgaps and chaotic bands.With the subwavelength cells, the generalized width reachesγ=21 in a 1D NAM and it goes up to γ=39 in a 2D NAM, which overcomesthe limit of bandwidth for wave suppression in current LAMs.Our work allows for further progress in the understanding of the dynamics of NAMs and it opens up avenuesindouble-ultra acoustic manipulations.