Estimation of the mean frequency of a quasi-monochromatic signal on a noise background

An analysis is made of the accuracy of the determination of the frequency of a process which is a mixture of a quasi-monochromatic signal and peripheral wideband noise; the investigation pertains to Doppler acoustic sounding of fluid flows with scattering particles. An expression is obtained for the frequency variance when it is determined over a duration T containing a fixed number of zero-level crossings by the process considered. This expression is valid for a wide class of correlation functions of the process considered and the transient response of the receiving system.