Most microphone array applications require sound source localization for subsequent multichannel signal processing algorithms. Steered response power-based source localization has been the most popular method due to its robustness against reverberation and background noise. Unfortunately, it requires a grid search method whose computational cost is proportional to the number of grid points, which makes it challenging for real-time applications. This paper proposes an efficient method for computing the steered response power by using two different techniques. Firstly we propose to separate pre-runtime computations from runtime computations. Secondly we vectorize the computations and group similar computations with a multi-threaded library (IPP) to efficiently exploit standard processing architectures. Experimental results show that the proposed method signicantly reduces the computational load of microphone array processing making it viable for real-time implementations on constrained devices.