Investigation and optimal design of band gap tunability in fractal phononic crystals Shuai Yang, Jia-Hao Yin, Xiao-Jing Zhu, Kai Wang, Shi-ke Zhang, Lu Cao, Peng-Yu Guo and Yong Liu Acta Acust., 9 (2025) 18 Published online: 07 March 2025 DOI: 10.1051/aacus/2025007