Fourier modal method with enhanced transmittance matrix for diffraction analysis of multilayer two-dimensional acoustic metamaterial gratings. - Guo, Zengxian; Li, Jia; Guo, Yingxian; Zhang, Songsong; Ma, Teng; Wang, Guojun; Wang, Qiang; Liu, Xiaoji; Zhang, Zhijia; Wei, Hao; Wang, Lin (Journal of the Acoustical Society of America, 2026)