SIGNAL FREQUENCY TRACKING METHOD

PROBLEM TO BE SOLVED: To improve precision of the tracking of a signal frequency. SOLUTION: An acoustic signal is received with an acoustic sensor 1, and the signal intensity distribution is obtaind by applying high speed discrete Fourier transform or the like. A past constant frequency amount of the signal intensity distributions is stored in a storage device 3. Neural networks 4-1 to 4-3 show large output values when signals exist in inputs and gradients are present in the charge ranges of the neural networks. By detecting the maximun point concerning the frequency axis with an event detecting equipment 5, a narrow band signal is obtained, and the gradient of the signal is obtained. Time integration is performed for every frequency by using two integration equipments 50-1, 50-2 having different integration times. The integration time suitable for the measurement of a signal having gradient is selected with an integration time selecting equipment 51. A precisely measured frequency is obtained with a frequency precision measurement equipment 20, and a precisely measured frequency is time-sequentially tracked with a tracking equipment 30.