Audio Forensics

An Audio Forensic expert applies a scientific approach to recovering, evaluating, enhancing, clarifying, and/or authenticating recordings to be used in court. The primary aspect of audio forensics is establishing the authenticity of audio evidence. This is especially important; often times audio recordings in criminal and civil litigation are presented by police or the opposing attorneys and may be miss interpreted. ​

Audio Authentication Process

1.  Evidence marking for later identification by the forensic expert

2.  Physical inspection of the evidence for specific characteristics that are noted by the expert

3.  Digital data imaging and playback anomalies

4.  Critical listening to the audio for auditory anomalies

5.  High resolution waveform analysis, visual inspection of sound wave formation

6.  Narrow band spectrum analysis

7.  Spectrographic analysis

8.  Digital data analysis

9.  Miscellaneous analysis based on the investigation thus far

10.  Work notes and work product

11.  Creating a forensic report

Once authenticity of the audio evidence is established, the forensic expert must rely on other techniques as well as their own expertise to determine the authenticity of the chain of custody, such as requesting the original.

Best Practice is That We Analyze the Original Evidence

If the original recording is on analog media, playback and duplication rely on physical processes that introduce noise and degrade the signal, even if slightly. A copy of an analog recording can never be an exact duplicate. An original digital recording is a bit stream from which the acoustic audio signal can be generated. Exact copies of that bit stream can be made. With digital evidence, each stage of copying can be exact, with no loss of quality between generations.

ANALYSIS

Enhancement/Clarification

More often than not, audio and video evidence is not clear enough to accurately hear and view the events as they occurred. This is where an expert can assist the trier of fact by performing forensic enhancement. One of the most common audio issues that we address during an enhancement is noise and other extraneous “unwanted” sounds. The noise floor is usually consistent throughout the recording. That means it can be removed to varying degrees by using noise reduction software. The most complicated issues are the extraneous sounds that are not continuous. These sounds could include anything from a plane flying overhead to someone whistling while people talk. These sounds are difficult to pinpoint with standard tools such as noise reduction and equalization, but they can be identified using a spectrogram. After critical listening, the forensic expert must use electronic measurement to examine the audio evidence.

Visual Inspection

Audio Editing Software

Analyzing Metadata in Digital Audio Evidence

Shows form with Metadata info

Digital audio recordings contain metadata which reveals information about how the recording was made. The metadata also determines the type of equipment that created the recording. If a recording was loaded into a software program capable of performing edits, there will often be a footprint left in the recording.

We can examine and analyze a variety of audio recordings, including but not limited to:

  • Phone calls
  • iPhone recordings
  • 911 Dispatch
  • Law Enforcement Dash Camera
  • Law Enforcement Wire Tap
  • Concealed Audio Recorders
  • Confidential Informant
  • CCTV Surveillance Audio
  • Voice Mail (butt dial)

If you have a video that you question or need help understanding, please give us a call (312) 818-4788. Any and all formats of audio and video accepted. Retainer agreement available on request; travel expenses will be quoted in advance excluding meal expenses and flat rate time for travel instead of hourly.