$$S_1$$ and $$S_2$$ are two identical sound sources of frequency 656 Hz. The source $$S_1$$ is located at O and $$S_2$$ moves anti-clockwise with a uniform speed $$4\sqrt{2}$$ ms$$^{-1}$$ on a circular path around O, as shown in the figure. There are three points P, Q and R on this path such that P and R are diametrically opposite while Q is equidistant from them. A sound detector is placed at point P. The source $$S_1$$ can move along direction OP.

[Given: The speed of sound in air is 324 ms$$^{-1}$$]