Abstract: The method disclosed consists in analyzing the vocal signals in consecutive windows, in quantifying, on a determined number m of levels, the vocal signal in each of the windows and in measuring, in each of the windows, the vocal signal in each of the windows and in measuring, in each of the windows, the r-m-s value of the samples of the vocal signal. It consists constructing, in a vector space with n dimensions having, as its first base, the unit vectors (E.sub.0 to E.sub.n-1) of the energies measured on n consecutive windows, a resultant energy vector E corresponding to the sum of n energy vectors measured respectively in n windows of analysis of the vocal signal, then in achieving, in this space, a change of base having, as its first main axis, an oriented axis of unit vector having, as its components, the unit vectors of the first base, to project, in the new base obtained, the resultant energy vector. Codings on q bits such that 2.sup.