AES Technical Committee

Audio Forensics

Chair:    Jeff M. Smith    (Send Email)
Vice Chair:    Daniel Rappaport    (Send Email)
Vice Chair:    Eddy Bogh Brixen    (Send Email)
Forum:    Committee Discussion Forum


Current Areas Of Work

This committee is associated with the following session at AES Los Angeles 2014:
Audio Forensics: An Overview
  • To extend knowledge of audio forensic practice and techniques world-wide
  • To identify areas requiring additional research
  • To bring together professionals and students in the area of audio forensics
  • To encourage publication of papers, and to arrange tutorials, conferences and workshops, within the AES
  • To support standards committees on forensic audio via fostering of refereed journal publications

Recent/Planned Activities

Another successful conference of the AES on Audio Forensics was held June 12-14 in London. See the website for specific program and sponsor details: aes.org/conferences/54. Proceedings from this conference, as well as the previous audio forensics conferences (26, 33, 39, 46) are available here: http://www.aes.org/publications/conferences/

At the AES 135th Convention in New York, several events of interest to audio forensics were held:

A selection of 135th convention events:

Several papers throughout the convention on signal analysis and enhancement, audio authentication, speech analysis.

- Thu 10:30 - 12:30 W4: "Acoustic Enhancement Systems - Implementations"

- Fri 9:00-10:00 TC-AF meeting; open to all AES members

- Fri 10:30-12:00 W11: Audio Source Separation

- Fr 10:30-12:00 T8: Automatic Speaker Recognition, Voice Biometrics, and Forensic Speaker Comparison: Putting it All Together

- Fri 2:00-3:30 W14: The Timeline Never Lies: Audio Engineers Aiding Forensic Investigators in Cases of Suspected Music Piracy

- Sun 9:00-10:30 W22: Classic Speech Intelligibility at the Royal Danish Theatre

Mission Statement

Audio Forensics refers to engineering and scientific analysis, evaluation and presentation of audio and acoustic evidence in a judicial inquiry normally leading towards a presentation in court. The complex challenges faced by the field transcend borders and jurisdictions, and becomes increasingly complex with the proliferation of new types of digital media. In order to establish a reliable scientific basis for the procedures and analysis of the outcomes of audio forensic analysis, the technical committee meets at AES conventions to plan conferences, workshops and tutorials; to encourage dissemination of scientific information through peer-reviewed journal and conference publications and posters; to provide support to the AES Standards Committee on Forensic Audio SC03-12; and to communicate educational opportunities in the field. Presently, the technical committee meetings for audio forensics are open to all attendees.

AES Audio Forensics Conference London June 12-14, 2014

Details have been announce for the upcoming Audio Forensics conference to be held in London June 12-14, 2014. See the conference website here: aes.org/conferences/54.

Authors please prepare your submission as a Full Paper for consideration by January 31st, 2014. The AES 54th Author portal will be open by December 1st.

Emerging Trends in Audio Forensics

Last updated: 10/31/2011

Enhancement -

The enhancement of forensic audio recordings remains the most common task for forensic audio practitioners. The goal of forensic audio enhancement is to increase intelligibility of voice information or improve the signal to noise ratio of a target signal by reducing the effects or interferences that mask it. Many tools are available through various software developers with the most common being noise reduction- either adaptive or linear. Difficulties in this area are caused by lossy data compression common to small digital recorders, data compression and bandwidth limited signals in telecommunications, and non-ideal recording environments common to surveillance and security. One growing area of research is the assessment of speech intelligibility with multiple papers presented on the topic at the AES 39th Conference on Audio Forensics in 2010.

Authentication -

The majority of audio media presented to the forensic examiner are digital recordings on optical disc, HDD, flash memory, and solid-state recorders. However, the analysis of analog tape cassettes and microcassettes is still required of examiners. In the area of forensic media authentication, digitally recorded audio files may be subject to various kinds of manipulation that are harder to detect than those in the analog domain. This leaves the forensic audio examiner with new challenges regarding the authentication of these recordings. Many new techniques have been developed in recent years for use in these analyses. These techniques continue to be published and presented through the AES Journal and proceedings of AES Conferences and Conventions. Among these techniques is the analysis of the Electric Network Frequency component (ENF) of a recording. If present, the remains of the ENF may be compared to a database of ENF from the same grid to authenticate the date and time the recording was made. In addition to automatic database comparison, it is possible to learn several other things from ENF analysis including whether portions of the recording were removed, if an audio recording was digitized multiple times, how the recorder was powered, and more.

Recent developments in digital audio authentication also include the Compression Level Analysis of an audio recording to determine if an uncompressed file had been previously subject to data compression or if the compression level present is consistent with an authentic recording. Also, a technique for determining the presence of butt-splice edits has been presented. In the digital domain, as in the analog, auditory and spectral acoustic analysis continues to be necessary. However, it is also clear that analysis of the digital data that makes up a recorded audio file including its header and file structure must be exploited to ascertain a digital recording’s authenticity.

Speech and Speaker Analysis -

The analysis of speech and speakers present on audio recordings is a large domain that intersects many industries including forensics and security. The analysis of speakers present in recordings to ascertain identity continues to be a common request of forensic audio examiners. However, “identifying” persons in a 1:1 comparison is not supported within the scientific community that favors “recognition” of persons based on extracted features relative to a background model representing a population of speakers. Automatic systems based on cepstral coefficients, Gaussian Mixture Modeling, and likelihood ratios employ robust and validated techniques for speaker recognition. This quantitative approach better measures and takes into account intra- and inter-speaker variation. When used in a forensic environment where trained examiners base conclusions on likelihood ratios, this technique is valued greatly over other qualitative analyses.

The capability of a system to process multitudes of audio signals and sort them based on language, topic, speakers present, and acoustic environment continues to progress with many new advances. An interesting area of research and its application in audio forensics is Computational Auditory Scene Analysis (CASA). This field of audio processing is interested in developing machine systems that perform automatic signal separation using principles derived from the human auditory system's perceptual abilities to understand audio scenes. CASA systems have already proven very useful as pre-processors for automatic speech recognition systems and in hearing aids. New areas of study include their use in audio forensics. Also, automatic speaker segmentation based on extracted spectral features and statistical modeling can help automated systems tasked with speech and speaker recognition.

Other Considerations -

Since the fundamental aspect of forensic audio is its application to law with the litigation process benefitting from audio enhancement and analysis, it is important for the practitioner working with forensic audio to be aware of this process and the need for proper evidence handling and laboratory procedures. As digital audio proliferates so to have the identification of proper practices for imaging media, hashing file duplicates, and recovering and/or repairing corrupt or carved files.

Additionally, it is not only common for forensic audio to be played in a courtroom but for typed transcripts of recorded conversations to be prepared for the individuals involved in a case; the lawyers, judge(s), and/or jury. Specific to these needs, there are developments in addressing the inherent bias present in the human preparation of these transcripts. Also, the forensic audio practitioner must be aware of the audio samples being presented taking into consideration courtroom acoustics, psychoacoustics, and the hearing abilities of these individuals.

AES Activities -

Numerous papers on audio forensics appear in the Journal of AES and are presented at AES Conventions each year. Additionally, there have been three AES Conferences on audio forensics since 2005(AES 26th, 33rd, and 39th) and the next will be in Denver, CO in 2012. Additionally, regular workshops and tutorials appear at AES Conventions. At the AES 130th Convention in London there was a tutorial on forensic audio enhancement. At the AES 131st Convention in New York there was a workshop on forensic audio authentication.


Meeting Report:

These documents do not necessarily express the official position of the AES on the issues discussed at these meetings, and only represent the views of committee members participating in the discussion. Any unauthorized use of these publications is prohibited. Authorization must be obtained from the Executive Director of the AES: Email, Tel: +1 212 661 8528, Address: 60 East 42nd Street, Room 2520, New York, New York 10165-2520, USA.

2014-5-23     135th AES Convention TC-AF Meeting Report
Description: TC-AF meeting minutes from the 135th AES Convention, New York, Oct. 2013

2013-9-3     134th Convention TC-AF Meeting Report
Description: May 2013 TC-AF meeting minutes

2013-9-3     133rd Convention TC-AF Meeting Report
Description: October 2012 TC-AF meeting summary

2013-9-3     132nd Convention TC-AF Meeting Report
Description: April 2012 meeting minutes

2013-9-3     131st Convention TC-AF Meeting Report
Description: October 2011 TC-AF meeting minutes

2013-9-3     130th Convention TC-AF Meeting Report
Description: May 2011 meeting minutes

2013-9-3     129th Convention TC-AF Meeting Report
Description: November 2010 TC-AF meeting minutes

2013-9-3     128th Convention TC-AF Meeting Report
Description: May 2010 TC-AF meeting minutes

2013-9-3     127th AES Convention TC-AF Meeting Report
Description: October 2009 TC-AF meeting minutes

2013-9-3     125th AES Convention TC-AF Meeting Report
Description: Oct. 2008 TC-AF meeting minutes


Committee Members

 Christoph Musialik  Durand Begault  Gordon Reid 
 Rob Maher  W.A. Deutsch  Eddy Bogh Brixen 
 Anibal Ferreira  Lise-Lotte W Tjellesen  J. Keith McElveen 
 Wes Dooley  Wanda Newman  Robert-Eric Gaskell 
 Margaret Luthar  Myke Roy  Erik Achrén 
 Ronny Max  Tom Owen  Mark Stebbeds 
 Robert Lusk  Ryan Hansen  Davis Appelt 
 Todd Makinen  Lars Clausen  Pascal Lorenz 
 Kuldip Raj  Thor Legvold  Florian Raschke 
 Sebastian Schneider  Michaela Schuster  Jeff M. Smith 
 Phil Manchester  Truls Birkeland  Jacob Setinhour 
 Andrey Barinov  Hafiz Malik  Matthew Owens 
 Sean Coetzee  Matthew Eardley  Norm Broner 
 Neil Muncy  Kristin Bidwell  Doug Gregory 
 Catalin Grigoras  Felix Klemke  Dan Nyberg 
 Jeff Harris  Vlado Delic  Daniel Rappaport 
 Federico Jankilevich  David Hallimore  Steve Saunders 

To request membership in this Technical Committee please email the Chair by using the link above.

 
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AES - Audio Engineering Society