Spectral ACF from the unresolved screen case with an injected Gaussian intrinsic pulse with a width of 3 ms. The main panel illustrates the host screen scintillation, while the inset highlights the narrower Gaussian self-noise resulting from the injected intrinsic pulse. To see the MW scintillation, we refer to the top panel in Fig. 8, as the IRF involved in producing both the plots are the same. The scintillation from the two screens peaks close to three, while the narrow self-noise peaks higher. This plot emphasizes the importance of distinguishing between scintillation and self-noise when dealing with pulses of finite width. A Gaussian intrinsic pulse results in a Gaussian self-noise curve, but a more complicated intrinsic pulse can produce self-noise of an unknown functional form. Even in such cases, one can estimate the width of the pulse from the self-noise in the spectral ACF.