are computed for the next loop during a sixth step 312 the function u03b1 defining the learning rate and decreasing over time is updated in an alternative embodiment of the present invention the fifth and sixth steps 310 and 312 are removed and a third prime and third double prime steps are inserted before the fourth step 308 the third prime step computes a new neighbour radius and the third double prime step computes a new learning factor finally in a seventh step 314 according to the first embodiment of the present invention the rough training period has concluded a first iteration further iterations may be initiated or the rough training phase 300 may be terminated fig4 shows the fine tuning phase designated in entirety by reference numeral 400 the fine tuning phase 400 is contrary to the rough training phase 300 a supervised process the object of the fine tuning phase 400 is to group any of the neurons 202 together according to probable acoustic program during a first step 402 the neurons 202 are extended and the extensions are initialised with random numbers the term u201c extension u201d is in this context to be construed as adding further parameter to each of the neuron the further parameter refers to an acoustic program during a second step 404 the radius and the learning rate is modified that is the radius is decreased and the learning rate is maintained however principally the neighbour weight and the learning factor may get new values which can differ from the initial rough training values during a third step 406 in addition to the.