Exploiting Nonnegative Matrix Factorization with Mixed Group Sparsity Constraint to Separate Speech Signal from Single-channel Mixture with Unknown Ambient Noise Journal title: EAI Endorsed Transactions on Context-aware Systems and Applications Authors: Thanh Thi Hien Duong, Phuong Cong Nguyen, Cuong Quoc Nguye Subject(s): Computer and Information Science, Data Communication and Networks