In a certain concert hall, echoes of the original audio signal x(n) are generated due to the reflections at the wall and ceilings. The audio signal experienced by listeners y(n) is a combination of x(n) and its echoes. Let y(n) = x(n) + αx(n+k) where k is the amount of delay in samples and α is its relative strength. We want to estimate the delay using the correlation analysis. Determine analytically the autocorrelation ryy(l) in terms of the autocorrelation rxx(l).