A method is presented for using noise spectroscopy to efficiently characterize random telegraph signal (RTS) in flash cells, in particular allowing the determination of oxide depth of the traps from the gate voltage dependence of the frequency spectrum of the trap. The RTS traps are not uniformly distributed in nitrided oxides, and increased nitridation of the tunneling oxide results in larger RTS specifically because of the proximity of the additional nitrogen to the substrate. The various effects of program/erase cycling on individual RTS related traps are qualitatively analyzed.