In this paper we propose a novel technique to localize planar obstacles through the measurement of the Direction of Arrival by a microphone array. The measurement of the Direction of Arrival of the reflected path is turned into a quadratic constraint where the unknowns are the line parameters of the reflector. A cost function that combines multiple constraints is then derived. A parametric description of the obstacle is found by minimization of the cost function. Some simulations and experimental results show the feasibility of the proposed method.