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stimmenvergleich.com offers forensic voice comparisons and a number of other forensic speech and audio services for government agencies, lawyers, and private clients. For voice comparisons we use proven auditory and instrumental phonetic analysis techniques based on specialist knowledge and years of casework experience.

With appropriate speech materials, speaker comparisons are made using modern and validated voice biometric methods. For that purpose stimmenvergleich.com uses cutting-edge language, text, and channel-independent Phonexia speaker identification software.


Dr. Gfroerer has recently retired as head of the Forensic Speech, Language and Audio specialist division within the German Federal Criminal Police Office (Bundeskriminalamt) Crime Lab. He has studied psycholinguistics, phonetics and psychology at the Ludwig-Maximilians-University in Munich. After earning a doctorate in the field of cognitive psychology, he was a research assistant in different projects at the Ludwig-Maximilians-University and at the Max Planck Institute for Psycholinguistics in Nijmegen, The Netherlands. In 1990 he joined the Forensic Institute of the Federal Criminal Police Office in Wiesbaden. His work focused on operation and control of forensic voice comparisons for penal courts and prosecution and on research and development in the field of voice biometric analysis. From 2000 to 2018, he was director of the Forensic Speech, Language and Audio specialist division of the Bundeskriminalamt. From 2006 to 2010 he was chairman of the ENFSI (European Network of Forensic Science Institutes) Expert Working Group Forensic Speech and Audio Analysis. In his career he has collaborated in the development of standards for forensic speaker recognition and authored numerous court reports and scientific papers. After his retirement in the end of 2018 he became a consultant and expert in private practice.



Comparison of different voice and linguistic patterns ("voice prints") with regard to possible speaker identity or non-identity using classical forensic-phonetic and validated biometric procedures. The process is sometimes referred to as forensic voice analysis, speaker recognition or voice identification.


Investigations of voice recordings for evidence of editing or tampering.


Writing down transcripts of difficult to understand or disputed utterances for investigative or evidential purposes.


Analyzing recordings of unknown speakers to reveal information about aspects of identity like regional accent, language background or any other which may be apparent from their speech.


Use of digital signal processing techniques to to remove extraneous noises in order to  improve the intelligibility or audibility of speech.


Preparation of an expert opinion or report based on national and / or international recommendations.

Contact stimmenvergleich.com to learn more about our services and what we can do for you.