Abstract: A method and apparatus for reducing sonar measurement error in noisy environment, by monitoring environmental noise spectrum over the range of operable sonar frequencies, and automatically changing the system sonar transmission frequency and its dependent components in order to avoid the detected interference frequencies. A wide band transceiver and a digital signal processor (DSP) can be used as a Frequency Server, and to monitor the environmental noise spectrum continuously through the use of Fast Fourier Transform (FFT) algorithm to produce noise frequency database for the Frequency Server. Each transmission cycle, the DSP dynamically getting frequency from the Frequency Server were noise is below a certain level for sonar transmission and adjust its dependent components accordingly. Thus, continuously maintains reliable measurements even in the presence of sporadic interference.