Let's say users log into a system using a voice-print. Software can read the input from the microphone, compare it to the stored sample, and tell the user "There is a
97.5% similarity to the voice-print stored on file", granting access depending on how sensitive it is. Due to the imperfections in microphones, air pressure chaos, and limited accuracy vocal-folds, no matter how hard the user tries, he will never be able to match his voice-print stored on file with complete accuracy.
On the other hand, if your security system uses a password string, you are able to require the password to be
100.0% correct, as it is possible for a user to perfectly replicate a password they have entered in the past.
What is the name of this type of "imperfect password", that the user cannot reasonably replicate with
100% accuracy? This would include finger/palm prints, retinal scans, voice-prints, and facial recognition.