Abstract: The longitudinal distribution of tone noise sources on a moving underwater vehicle can be estimated via the minimum point appearing on the instantaneous frequency rate curves of Doppler signal received by a single sensor measuring system. A time-frequency rate distribution referred to as L-Phase Distribution (LPD) and an iteration algorithm to realize the discrete-time LPD are proposed to extract the IFR curve of Doppler signal. Together with the velocity of vehicle, the measurement of the distribution of tone noise sources with different frequencies on underwater target can be achieved. The sea experiment results give out estimation errors for three different operating frequencies: 105 Hz, 220 Hz and 500 Hz. The values of these errors are all less than 2.5 m, which approve the effectiveness of the new method for middle and low frequency noise sources.