Audio authentication

Audio authentication examines whether a recording is consistent with its claimed origin and history. The question might concern an apparent edit, a disputed pause, or whether a file matches the way someone says it was recorded.

That history is often called provenance. It includes how the recording was made, which version is available, and what happened as it passed between people or systems. A file that sounds continuous can still need examination; an unusual sound can have an explanation other than deliberate editing.

For casework, start with the claim you need tested. “This conversation is said to be continuous, but the background changes at 02:15” gives an examiner a specific issue to assess. Keep the observation separate from a proposed explanation. You don't need to decide which forensic technique should be used before asking for help.

No. Authentication concerns a recording's integrity and history. Enhancement aims to make captured sound easier to hear, while transcription represents audible speech in writing.

Scroll sideways to compare all three columns.

If you need more than one result, describe each question before further processing. Keep the source and any listening copies separately. Our comparison of enhancement, transcription and authentication explains how the services fit together.

A pause or sudden sound change can identify a passage to examine, but it does not by itself prove that someone edited the file. Recording behavior, a pause-and-restart event, a fault, or later processing may also explain an apparent discontinuity.

Write down where the change occurs and what you hear: for example, “The background hum drops at 02:15, then the next sentence begins.” Retain enough material before and after it to preserve the context. Avoid repeatedly exporting a short clip as your only surviving version.

SWGDE's digital-audio authentication guidance includes a worked example in which comparison with test recordings supports a recorder pause/restart event. That example illustrates why a visible or audible break needs interpretation.

The useful next question is whether the observation is consistent with the stated recording process. An examination can bring together the file, its sound and its known history to test that claim.

An examiner defines the question, assesses the available material and chooses tests that can address the claim. Digital-audio authentication commonly considers the file's structure, the recorded signal and, where appropriate, comparison recordings.

SWGDE's approved version 1.3 describes a systematic examination using applicable tests together. The techniques below explain the kinds of information an examiner may consider; the agreed work must fit the actual file and question.

A file's format and metadata can help explain how it was created or processed. Metadata is information stored with the recording, such as an identified device, encoding settings or recorded dates.

An examiner can compare those properties with the claimed recording system and known file behavior. An editing-application entry may warrant investigation, but it does not explain every action taken with the file. Equally, missing metadata is not proof of tampering. Some copies or conversions lose information that was available in an earlier version.

The sound can reveal changes worth testing, including shifts in background noise, abrupt transitions and patterns around the start or end of a passage. Critical listening can direct attention to those areas.

A waveform shows changes in the signal over time. A spectrogram displays frequency content over time. Those views can help an examiner locate and compare events, but a conspicuous shape alone is not an authenticity verdict. The recording conditions and other test results still matter.

Test recordings can help distinguish normal behavior of a recording system from an unexplained feature in the questioned file. The comparison needs relevant equipment, software and settings where those affect the claim being tested.

For example, a recorder may leave a characteristic change when recording stops and resumes. Reproducing that behavior can help assess a similar change in the submitted file. Tell the reviewer whether the original device or application is known and still available. Keep it available for discussion rather than experimenting on the source yourself.

Keep the original recording unchanged, along with the version you received and any earlier or processed versions. Tell the reviewer which file is believed to be the original and how each copy was obtained.

The earliest available file may preserve information that a converted, cleaned or re-recorded version does not. SWGDE distinguishes the original recording from a transcoded version. A decoded copy can still contain useful audio information while no longer supporting examination of the original file format.

A chain of custody records who handled the recording and how it was transferred or stored. Keep the history you have, while making missing steps clear. That history supports the examination; it does not establish authenticity by itself.

If all you have is an exported voicemail, an app attachment or a forwarded recording, keep it as received. Explain that limitation and ask whether the available version can address your question. A copy is not automatically useless, and a convenient file type is not automatically the best source.

• Label the original and working copies distinctly.
• Record known transfers, exports and processing without guessing missing history.
• Keep the complete recording when you provide a timestamp or passage of interest.
• Discuss sensitive-file handling before arranging a transfer.

Before sending sensitive case material, ask which transfer route to use, who can access the recording and how long files will be retained. Agree any sharing restrictions directly before sending the file.

A finding can explain whether the examined recording is consistent or inconsistent with the claim tested, or whether the available information is insufficient to decide. Its meaning depends on the question, material and tests.

SWGDE's approved version 1.3 describes consistent-with-original, inconsistent-with-original and inconclusive conclusions. An inconclusive finding leaves the issue unresolved. It does not confirm authenticity or establish manipulation.

Ask what supports the conclusion and which limitations remain. A finding that a file has been re-encoded may be different from a finding that recorded speech was rearranged. A recording consistent with the claimed device does not automatically establish the truth of everything said in the conversation.

If AI-generated speech or voice cloning is your specific concern, name that question at the outset. Ask whether the proposed work can address that concern and what limits apply before commissioning it.

Tell the reviewer about the proceeding and any documentation requirements before you commission work. A technical authenticity examination and the legal foundation for admitting a recording are separate questions.

SWGDE explains that “authentication” is also used in a legal context: a person involved in the events or recording process may establish that playback reflects what occurred. A scientific examination can test a disputed claim, but it does not itself promise court acceptance.

Ask whether the person doing the proposed examination has the relevant qualifications, how findings will be explained, and whether the deliverable meets your stated need. If you require a written expert report, a declaration, deposition support or testimony, identify that requirement explicitly. Confirm availability and scope rather than assuming these are included in restoration or authentication.

Describe the recording, the specific concern and the decision you need to make. Give the reviewer enough factual history to assess the work without asking them to confirm a conclusion.

1. Identify the available material. Say whether you have the original, a direct export, a forwarded copy or several versions. Include the device or app if known.
2. State the claim or observation. Give the relevant timestamps and describe the sound or difference between versions. “The sound changes here” is more useful than “Prove this was forged.”
3. Explain known handling. List transfers, conversions and previous cleanup. Keep unknown details marked as unknown.
4. Name the intended use. Explain which question matters to the case and what documentation you need.
5. Give the actual deadline. Distinguish the date you need a reply from the date you need completed work. Discuss sharing restrictions before sending sensitive material.

The scope discussion should establish whether the available material is suitable, what examination is proposed, what you will receive, and the cost and timing. Ask for those points to be clear before deciding.

Media Medic offers authentication as a paid addition to restoration, with its scope agreed separately. Tell us what concerns you about the recording's history and what you need checked.

Start with a free file review. An audio engineer listens to every file to assess restoration before an invoice is sent. That initial review helps open the discussion about the work you need; a completed authentication examination is separate paid work.

Ask about the authentication scope, suitable material, deliverables and timing before commissioning it. Pricing is discussed directly. If you also need restoration, normal turnaround is five days or less and a paid 24-hour upgrade is available. Confirm the timing for the particular work you request.

Request a free file review and describe the recording, the concern and your deadline.