Forensic audio evidences

[nrochon]

Hi,

 

I'm analyzing an audio mp3 file for tampering evidences. I need help to find evidence. We known than the file has been tampering. This file show some anomalies. This file is a court room recording.

 

 

• Silence segments from this file are different than other files recorded the same day at the same room (more quiet like if only one person was alone in the room when it suppose to be 4 persons)
  
• I analyse the sound and waveform and I find a bio-metric anomaly (the person how talk do not take a breath like she did usually after her speech at the beginning of the tamperized segment )
  
• We heard a unusual beginning of word from her going rapidly down at the beginning of the tampering.
  

 

 

I'm computer scientist (master degree) but not specialized in audio files investigations. I read a lot about technical analysis but I need some opinions and cues.

 

I would appreciate to find a way to search for repeated segments in audio file (like identical sample). The only way I find is to convert the file in WAV format to uncompressed it and search for HEX words. Do you know a free software to do that ? (Like copy this segment and search for it in this MP3 file).

 

Could someone can help me to investigate this file. I could show some images of the wave form, wave DB, Spectogram and Frequency Plot Analysis. Any technical information are welcome.

 

Images :

https://drive.google.com/drive/folders/0B3lgUEjpniRsbC1WbmdZNkpjanc?usp=sharing

 

I used two different software Audacity and WavePad.

The work as been done by a specialist, the basic mistakes has been avoid.

 

P.S; Excuse my English, I'm french.

 

Best Regard

 

NR

[The Computer Audiophile]

Interesting. There are some incredibly smart people here in the CA community. I hope they can help with this.

[nrochon]

Interesting. There are some incredibly smart people here in the CA community. I hope they can help with this.

 

Thank you, ... I can add more information or files if needed

[NOMBEDES]

Maybe this thread would get more attention at:

[h=2]

Music Analysis - Objective & Subjective[/h]

 

[Allan F]

Given that it relates to a court recording, you are probably going to require the assistance of an expert in the field. While I am not familiar with any such experts, you might want to contact the people at the following link that I found online: Forensic Audio Enhancement - Forensic Audio Analysis

[nrochon]

I contacted some experts

 

But there prices turn arround 3000$-12000$us

[mansr]

I contacted some experts

 

But there prices turn arround 3000$-12000$us

Seems reasonable to me.

[mansr]

I would appreciate to find a way to search for repeated segments in audio file (like identical sample). The only way I find is to convert the file in WAV format to uncompressed it and search for HEX words. Do you know a free software to do that ? (Like copy this segment and search for it in this MP3 file).

 

You'll never find exact matches, especially not after mp3 compression. You'll need to use something like cross correlation between small segments. Matlab can do it, or there's probably specialised software that's more efficient.

[davide256]

I would think that if the tape was altered (edited) you would find spectrum discontinuities that a good spectrum analysis program could highlight as gaps or insertion boundaries. MP3 will alter the original full frequency integrity but the merge points should still show up as discontinuities in a spectrum analysis graph pf the mp3

[Audio_ELF]

If the original is a court room recording; doesn't the court have a definitive version?

[mansr]

If the original is a court room recording; doesn't the court have a definitive version?

 

Unless someone managed to tamper with it. That would be a pretty serious offence, obviously.

[Audio_ELF]

Unless someone managed to tamper with it. That would be a pretty serious offence, obviously.

I don't know about elsewhere ... but I would have expected that court transcripts (like police interviews) would be recorded directly to a write once media and multiple copies.

 

The OP might want to ascertain the source of the recording and if other version are available.

 

It does seam a strange request / question as unless the OP is an expert in such things (and they state they aren't) then any discoveries they make of tampering of the recording is going to be of doubtful worth in any legal case (I would have thought).

 

Or is this just academic interest or are we helping with your homework?

[nrochon]

I asked for the MD5 electronic signature from the tribunal of the original audio file but they refused.

 

This could be a way to compare the MP3 I received and it original.

[nrochon]

I think every official recording most have a electronic tattoo (beat) to avoid tampering.

 

Technology allow that possibility

[Sam Lord]

You could contact a mastering engineer in France (perhaps at Harmonia Mundi) and ask them to simply listen to the recording and ask their opinion. That wouldn't cost terribly much. If they are convinced there is tampering, they might be willing to write a letter to the court stating that opinion. While it is not as valuable as expert testimony from a forensic audio engineer, it might be enough to affect the case.

[mac_and_dac]

Hi,

 

I'm analyzing an audio mp3 file for tampering evidences. I need help to find evidence. We known than the file has been tampering. This file show some anomalies. This file is a court room recording.

 

 

• Silence segments from this file are different than other files recorded the same day at the same room (more quiet like if only one person was alone in the room when it suppose to be 4 persons)
  
• I analyse the sound and waveform and I find a bio-metric anomaly (the person how talk do not take a breath like she did usually after her speech at the beginning of the tamperized segment )
  
• We heard a unusual beginning of word from her going rapidly down at the beginning of the tampering.
  

 

 

Is this a jury-based court case? If so, then why not present the same evidence that has convinced you that this file has been tampered with?

 

If it has convinced you, then maybe the jury will find it equally convincing?

 

I think it will be very hard to analyse a compressed audio file in any formal way that can demonstrate intentional tampering.

 

Anyway, good luck!

[blownsi]

Here in the hobby audio world there are some programs which could help but they are really only going to reveal anomalies in the recording. They will not give a definitive answer. Some of those anomalies will exist just because of the MP3 compression. At the end of the day you would still need an expert witness' opinion or to get jury buy in. The former would cost you serious money and the latter would be hard to do. My suggestion for the latter is to ask someone here to manipulate another file (such as reading from a book) in a similar manner trying to reproduce the artifacts in which you suspect. If you can get similar artifacts to be obvious to the jury they should have a reasonable doubt that the recording is contaminated.

[nrochon]

This recording don't come from an official tribunal, but from an administrative one.

There is evidences of tampering in. But these evidences can be contested on the custody chain to retrieve the copy.

I find two experts to give me an opinion.

[topofdaworldma]

A very popular and legally accepted programme for this type of thing is Diamond Cut Forensics. In the right hands it can work wonders.

 

Maybe they have a trial period or if this is something you want use to use more, then possibly a purchase at less than half that of the quotes you had!

 

Diamond Cut Forensics10 Audio Laboratory [DCP-920F] - $1,499.00 : Diamond Cut Productions, Professional Audio Restoration Tools

[nrochon]

A very popular and legally accepted programme for this type of thing is Diamond Cut Forensics. In the right hands it can work wonders.

 

Maybe they have a trial period or if this is something you want use to use more, then possibly a purchase at less than half that of the quotes you had!

 

Diamond Cut Forensics10 Audio Laboratory [DCP-920F] - $1,499.00 : Diamond Cut Productions, Professional Audio Restoration Tools

 

Interresting

There existe also certification for USA but I don't thing there course and official certificate in Canada (I come from Canada)

[Allan F]

Is this a jury-based court case? If so, then why not present the same evidence that has convinced you that this file has been tampered with?

 

If it has convinced you, then maybe the jury will find it equally convincing?

 

I think it will be very hard to analyse a compressed audio file in any formal way that can demonstrate intentional tampering.

 

Anyway, good luck!

Given that the OP is admittedly not an expert regarding this issue, I would not expect a court to find that his evidence is admissible to be presented to a jury, or a judge for that matter. In specialized fields outside the knowledge or experience of ordinary people, only qualified experts are allowed to offer opinion evidence in court.