The use of scientific investigation, technology, and tools to determine the authenticity of sound for civil or criminal cases is known as audio forensics. Audio forensics findings can be used as evidence in a variety of legal cases ranging from divorce to industrial espionage. Audio forensic analysis is also commonly used on surveillance tapes in cases involving employers or employees of a particular company.
The military and government of the United States have a long history with audio forensics. The technology was used in World War II to identify the voices of targeted enemies heard over radios and telephones. The use of a sound spectrograph, which plotted the frequencies and amplitudes of voice patterns, assisted analysts in identifying people of interest. Audio forensics has been used to analyze messages created terrorists in recent years to help pinpoint their locations, the time the audio was created, and other originating factors.
Background noises, voice frequency changes, noises emanating from recording equipment, and stop, start, and pause signatures are some of the things that are commonly evaluated in an audio clip to determine its authenticity. Any break in these areas could indicate to the analyzer that the recording is fake or has been tampered with. These discontinuities can sometimes be obscured background noise, necessitating additional investigation.
To identify an unknown sound, one of the most common techniques used during analysis is to compare it to a known sound. This is useful in situations where one speaker has been identified but the other has not. Voices can be identified prosody, vowel formant trajectory, pitch striations, breath patterns, nasal resonances, speech pathologies, and more. However, voice identification remains a complex and contentious issue, and many people believe that forensics analysis of voice identification and recognition is unsuitable for court submission and lacks credibility.
The use of signatures is also emphasized in forensic audio analysis. Audio signatures from specific controlled sources are used many audio forensic analysts. When an audio analyzer works with frequencies from electrical power sources, this is an example of this. An electrical socket can provide all of the answers to these analyzers’ audio forensics questions.
While forensic analysts now have access to a wide range of digital tools and programs, the amount of work involved in evaluating a piece of audio remains substantial. Analyzers may have to listen to the same piece of audio hundreds of times. Discontinuities can be difficult to detect, but not impossible for a trained and dedicated forensic audio analyst.