The purpose of this paper is to propose a robust technique for a sound
source localization based on the time difference of arrival in noisy or reverberant environments.
In the proposed technique, a nonlinear minimization problem for estimating source positions is formulated as a constrained optimization problem in consideration of a room capacity.
Then, a penalty function for a feasible region of this problem is used as the objective function.
As a result, only estimation results within the room can be obtained.
It is shown by several numerical experiments that estimation accuracy by using the technique can be improved about 50[%].