Abstract: Provided is a sound source determining system which can accurately and economically identify the position of aircraft in an airport or the like. The direction of a sound source is determined by arranging a plurality of acoustic sensors (S0, S1, S2, S3, . . . , S-1, S-2, S-3, . . . ) in an array at a prescribed interval for detecting an acoustic signal produced from the sound source, connecting a plurality of delay circuits (D0, D1, D2, D3, . . . , D-1, D-2, D-3, . . . ) having delay times which are different from one to a next by a unit time period (.tau.) to the outputs of the acoustic sensors, adding up the outputs of the delay circuits in an adder circuit (AD), and determining the direction of the sound source according to the unit time period (.tau.) which will maximize the output of the adder circuit.