In this paper, we propose a method for simultaneously estimating each TDOA in a multi-loudspeaker environment using GCC-PHAT. Conventional TDOA estimation systems typically generate sound exclusively from a single loudspeaker, even in the presence of multiple loudspeakers, and estimate the TDOA individually. However, the accuracy degrades significantly when sound sources are present simultaneously from multiple loudspeakers. In this paper, we propose an arrival time estimation method based on the GCC-PHAT method to solve this problem. The proposed method allows detection with mixed sounds, which is not possible with conventional methods. The results of evaluation experiments using computer simulations confirm that the proposed method can estimate the arrival time of each loudspeaker in an environment where sound is played from two loudspeakers. In addition, as a result of changing parameters such as embedding intensity, ratio of frequencies, and time, it was confirmed that under certain conditions, the arrival time estimation and distance estimation errors were smaller than those of the conventional method. As a result, this proposed method reduces the arrival time estimation error and distance estimation error to zero for the two types of sources.