MUGEN: Evaluating and Improving Multi-audio Understanding of Large Audio-Language Models. - Chih-Kai Yang; Yun-Shao Tsai; Yu-Kai Guo; Ping-Le Tsai; Yen-Ting Piao; Hung-Wei Chen; Ting-Lin Hsiao; Yun-Man Hsu; Ke-Han Lu; Hung-Yi Lee (CoRR, 2026)