Passive sound telemetry method

A passive sound telemetry method, comprising the steps of:

• receiving sound signals coming from a source located in a direction .theta..sub.0 at a distance D.sub.0 wherein said sound signals are received at a central sensor which is surrounded by at least two outer sensors located at a distance L from said sensor and wherein said sensors emit electrical signals in response to said received sound signals;
• making a first correlation between the electrical signals emitted by said central sensor and one of said outer sensors in order to obtain a first correlation signal C.sub.12 (t.sub.1) as a function of a first parameter t.sub.1 ;
• making a second correlation between the electrical signals emitted by said central sensor and another one of said outer sensors in order to obtain a second correlation signal C.sub.23 (t.sub.2) as a function of a second parameter T.sub.2 ;
• selecting a first arbitrary value T.sub.1 of the parameters t.sub.1 and t.sub.2 ;
• adding on a point by point basis the two signals C.sub.23 (t.sub.1) and C.sub.23 (t.sub.2) and assigning values T.sub.1+D for T.sub.1 and T.sub.1-D for T.sub.2 wherein said values are symmetrical around the value T.sub.1, in order to obtain a third signal C(t.sub.3) as a function of a third parameter t.sub.3 wherein the maximum C.sub.1 of said third signal and the value D.sub.1 of the value t.sub.3 corresponding to said maximum C.sub.1 are determined;
• and
• repeating said steps in an iteration for a series of values of t.sub.1, the absolute maximum C.sub.M, taken by C.sub.1 for said series of values and determining the values of T.sub.0 and D.sub.0 of T.sub.1 and D.sub.1 corresponding to said series of values;
• and
• determining the direction .theta..sub.0 and distance R.sub.0 from the formula;
• T.sub.0 =[(1/c) sin .theta..sub.0 and D.sub.0 =(L.sup.2 /2ROc) COS.sup.2 .theta..sub.0 where c is the speed of sound.