Voice Identification Aural Comparison and Collection of Examplar


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Aural/Spectrographic Voice Identification is defined as a combination of both aural (listening) and spectrographic (instrumental) comparison of one or more known voices with an unknown voice for the purpose of identification or elimination.

Voice Identification

This type of forensic voice analysis is based on the principle that each voice is individually characteristic enough to distinguish it from others through scientific voice analysis.

Factors in determining voice uniqueness lie in the size and configuration of the vocal cavities, such as the throat, nasal, and oral cavities, and the shape, length and tension of the individual’s vocal cords. Another factor in determining voice uniqueness lies in the manner in which the articulator muscles are manipulated during speech. Factors, which are also compared, are resonance quality, pitch, temporal factors, inflection, dialect, articulation, syllable grouping and peculiar speech characteristics.

Collection of Exemplar

It is recommended that the exemplar of the known voice must be collected in as close to the same manor as the recording of the unknown voice was recorded. For example, if the recording of the unknown voice was recorded over the phone, the exemplar of the known voice should be collected over the phone, etc. When the exemplar is collected, the suspect is asked by the examiner to stay the same words in the same way as they were spoken by the unknown person. In other words, in a normal, natural voice.

Audio Waveform of Gun Shots over Cell Phone Aural and Waveform Analysis

Analysis is done through aural (listening), and visual comparison of the words through graphical (waveform) display. Each recording is fed into a forensic computer using a digital sound card to ensure the best quality capture. A graphical display of the recorded material, called the waveform can then be viewed as the recording is played and listened to. The configuration of the individual words can be seen as they are played.

Spectrogram, Audio and Voice Forensic Analysis Comparison Authenticity Spectrographic Analysis

Our computerized spectrograph analysis facilitates visual comparison of the features of each word spoken. The spectrogram displays the speech in three formats; time, frequency and amplitude. The spectrogram serves as a permanent visual record of the words spoken and facilitates visual comparison of similar words spoken by an unknown speaker’s voice and a known speaker’s voices. The spectrograph shows time along the horizontal axes, and frequency along the vertical axis. Amplitude is indicated in varying degrees of gray shading.

Selection of Words for Comparison

After the evidence recording is received, the recorded speech is captured to a lab computer. The recording is carefully reviewed by our forensic experts to identify the words that will be best usable for comparison. The words sought are those which are most clearly articulated, not slurred, truncated or run together with other words. Each group of words selected is then placed into what is referred to as a short term memory file. The desired number of words per comparison is 20 or more.

Standards for Comparisons Determination

The following are the standards accepted nationally by all professional organizations involved with voice identification, including the FBI, Audio Engineering Society, the International Association for Identification, and the American Board of Recorded Evidence:

IDENTIFICATION: At least 90% of all comparable words must be very similar aurally and spectrally, producing not less than twenty (20) matching words. The voice samples must not be more than six (6) years apart.
PROBABLE IDENTIFICATION: At least 80% of the comparable words must be very similar aurally and spectrally, producing not less than fifteen (15) matching words.
POSSIBLE IDENTIFICATION: At least 80% of comparable words must be very similar aurally and spectrally, producing not less then ten (10) matching words.
INCONCLUSIVE: Falls below either the Possible Identification or Possible Elimination confidence levels and/or the examiner does not believe a meaningful decision is obtainable due to various limiting factors.
POSSIBLE ELIMINATION: At least 80% of comparable words must be very dissimilar aurally and spectrally, producing not less than ten (10) words that do not match.
PROBABLE ELIMINATION: At least 80% of the comparable words must be dissimilar aurally and spectrally, producing not less than fifteen (15) words that do not match.
ELIMINATION: At least 90% of the comparable words must be very dissimilar aurally and spectrally, producing not less than twenty (20) words that do not match.

As experienced expert analysts, our highly trained and qualified forensics team uses top of the line hardware and software technology to carefully handle and thoroughly analyze your evidence audio, video, and photographic media. We can isolate, separate, enhance, and authenticate all relevant aspects of audio and video recordings in order to produce expert evidence backed by many years of master experience. As an expert witness in the courtroom, our testimony from the witness stand will contain provable facts and relevant demonstrative evidence that can often make or break a case.

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Relevant areas of Voice Identification include Audio Forensics, Audio Enhancement, Audio Video, Voice Comparison, Voice ID, Audio Authentication and Authenticity Analysis, Audio Expert, Audio Analysis for Timing and Sequence of Events, Expert Witness, Tape Analysis, Audio Acoustical Analysis and Sound Measurement, Forensic Tape Analysis, Audio, Forensic Transcription Services, Voice Recognition, Gun Shots and Gun Shot Analysis.

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