ETFE.hpp emulates MATLAB's tfestimate, pwelch, and cpsd functions. It calculates the experimental transfer function estimate between input x and output y txy, the power spectral densities pxx and pyy, and the cross spectral density pxy. By default, it behaves exactly as MATLAB's functions, and similarly can be provided with specified windows, overlap, and FFT sizes. The output has been tested to precisely match that of MATLAB's (see matlab\test.m).