Evaluation of Batvox 4.1 under conditions reflecting those of a real forensic voice comparison case (forensic_eval_01)

Batvox 4.1 by Agnitio was tested under conditions reflecting those of a real forensic voice comparison case. This is part of a validation of Batvox 4.1 that is being conducted at the Netherlands Forensic Institute. There was considerable mismatch between the known- and questioned-speaker-condition recordings in the training and test data. Batvox allows for training data in the form of a reference population sample in which the recordings should be like the known-speaker recording and in the form of imposters in which the recordings should be like the questioned-speaker recording. Four settings of Batvox were tested that used the training data differently. These were the factorial combination of: using versus not using imposters, and using all 105 speakers versus a selected subset of 30 speakers as the reference population sample. Better performance was achieved when recordings from all 105 speakers in the training set were used as reference population data than when a subset of 30 of these were selected by Batvox. Better performance was also achieved when an imposter set of recording from all 105 speaker in the training set was used than when no imposter set was used.