Patent US 4,100,370

This system verifies the voice of a specific speaker (A) through verification of vocal sounds which form a previously-recorded recognition phrase spoken by A and others. Parallel filters derive a spectral characteristic parameter x.sub.i which contains weighting factors .alpha..sub.i, .beta..sub.i, and which represents a corresponding vocal sound x.sub.i. Improved specificity over other speakers is attained by a Characteristic Feature Extractor which varies .alpha..sub.i, .beta..sub.i, through p different values, thus deriving a set of p parameters (x.sub.ik) for each vocal sound x.sub.i, thus allowing emphasis of the specific vocal sound x.sub.i as spoken by a specific speaker, over that of competing sounds and speakers.