Audio recordings of the final conversations between pilots of the missing Malaysian jet and teams of air traffic controllers on the ground were "edited" before they were made public, voice experts say.
The tapes also appear to be recorded by at least two different audio sources, one of which may have been a digital recorder held up to a speaker, they said.
The analysts cautioned that their observations don't necessarily imply anything about the investigation into the missing flight.
The quality and brevity of the interactions between the cockpit and controllers made it impossible to glean any information about the pilots' state of mind before the plane disappeared, or even to determine whether both the pilot and co-pilot were speaking or if just one can be heard.
The audio recordings were published Thursday for the first time as part of a preliminary report by Malaysian authorities. In the report, Malaysia's Air Accident Investigation Bureau said a lack of real-time tracking devices caused "significant difficulty" in the hunt for MH 370, which disappeared March 8.
Listen to Air Traffic Control Interaction With Flight MH370
Analysts who listened to the recordings for NBC News did not know why they were edited, but discovered at least four clear breaks in the audio that indicated edits.
"It's very strange," said audio-video forensic expert and registered investigator Ed Primeau of Primeau Forensics, who has analyzed hundreds of audio recordings. He said the beginning and end of the recording are high-quality with a low noise floor, meaning ambient background noise is almost silent, unlike the middle.
"At approximately 1:14 (a minute, 14 seconds into the audio, which can be heard here), the tone of the recording change to where to me, it sounds like someone is holding a digital recorder up to a speaker, so it's a microphone-to-speaker transfer of that information. That's a pretty big deal because it raises the first red flag about there possibly being some editing," he said.
The next part that raises questions is two minutes, six seconds in, through two minutes, nine seconds in, he said.
"I can hear noise in the room, along with the increase in the noise floor. I can hear a file door being closed, I can hear some papers being shuffled. so I'm further convinced that, beginning at 1:14 continuing through 2:06 to 2:15, it's a digital recorder being held up to a speaker."
Long gaps in the communication throughout the recording also imply some editing, he said.
"But yet, at 6:17, there's a huge edit because the conversation is cut off. It's interrupted. And the tone changes again," he said. "The noise floor, when you're authenticating a recording from a forensic perspective, is a very important part of the process. All of a sudden, we go back to the same quality and extremely low noise floor that we had at the beginning of the recording."
Kent Gibson, a forensic audio examiner with Forensic Audio in Los Angeles, added that there appear to be additional edits at 2:11 and 5:08, and agreed it sounded as though the middle section was recorded with a microphone near a speaker.
"You can hear, at 4:07, pages turning or a person breathing, which is unusual," he said.
While it's not uncommon for the background of a recording to change when a cockpit communication turns over from ground control to air controllers — which happened about four minutes into this recording — that doesn't explain the noises that are heard.
"It's not unusual that there would be clicks when they push the button on the microphone, but it's very unusual to have a disturbance. Normally you wouldn't have any background," Gibson said.
A cut-off word also isn't out of the realm of possibility, he said.
"It wouldn't be unthinkable to have a truncated word because if somebody let go of the trigger on the microphone, it might cut off their word," he said. "But it would be very unusual to find a background differential at the same time, suggesting that Malaysian authorities or whoever presented this made edits for whatever reason."
Gibson said it’s possible the tapes could have been edited by Malaysian authorities "if the pilot dropped a hint that they didn't want to get out, if he said something that doesn't fit with the Malaysian government's party line."
But, he said, "It's more likely to be an inadvertent thing. But it's not the way to handle evidence."
The recording also could have come from different sources, he added.
"You can assume that the recording while they're still on the ground came from the tower and then you could assume that the communication with air controllers was while they're in the air," he said. "They may have just mishandled the cobbling of it together."
This doesn't necessarily prove anything about the investigation, he added.
"Unfortunately, there are no smoking guns, except there are edits. And there are clear edits," he said.
Tom Owen, a consultant for Owen Forensic Services audio analysis and chairman emeritus of the American Board of Recorded Evidence, said edits were to be expected.
"There's things that have to do with timelines and radar that they have available, but they don't make them available," he said. "They wouldn't give you anything that would be enlightening for the public to any secretive information. I don't see that as a problematic issue."
Primeau disagreed.
"This is not a good maneuver or a good faith move by the Malaysian government because of all these questions with regard to the different anomalies and edits that are in this recording," he said.
Audio experts felt the quality of the transmissions was too low to offer analysis of the pilots' voices.
Forensic audio expert Paul Ginsberg said even after enhancing and slowing down the conversations, there wasn't good enough, or long enough, sound samples to make a determination on the pilots' stress level.
"It's analogous to blowing up a photograph. It's the same amount of information," he said. "I don't know that any such determination would be admissible." - NBCNews
Below is the full transcript of that conversation, which was released by authorities earlier this month.
Transcript of Audio:
"ATC Delivery" (Pre-Departure)
Mayalsia Airlines Flight 370 cockpit (12:25:53): Delivery MAS 370 good morning.
Air traffic control (12:26:02): MAS 370 standby and Malaysia Six is cleared to Frankfurt via AGOSA alpha departure 6,000 feet squawk two one zero six.
ATC (12:26:19): ... MAS 370 request level.
MH370 at (12:26:21): MAS 370 we are ready requesting flight level three five zero to Beijing.
ATC(12:26:39): MAS 370 is cleared to Beijing via PIBOS a departure 6,000 feet squawk two one five seven.
Cockpit (12:26:45): Beijing PIBOS a 6,000 squawk two one five seven MAS 370 thank you.
ATC (12:26:53): MAS 370 welcome over to ground.
Cockpit (12:26:55): Good day.
"Lumpur Ground" (Kuala Lumpur airport ground movements)
Cockpit (12:27:27): Ground MAS370 good morning Charlie One requesting push and start.
ATC (12:27:34): MAS370 Lumpur Ground morning push back and start approved Runway 32 right exit via Sierra 4.
Cockpit (12:27:40): Push back and start approved 32 Right Exit via Sierra 4 POB 239 Mike Romeo Oscar.
ATC (12:27:45): Copied.
Cockpit (12:32:13): MAS377 request taxi.
ATC (12:32:26): MAS37..... (garbled) ... standard route. Hold short Bravo.
ATC (12:32:30): Ground, MAS370. You are unreadable. Say again.
ATC (12:32:38): MAS370 taxi to holding point Alfa 11 Runway 32 right via standard route. Hold short of Bravo.
Cockpit (12:32:42): Alfa 11 Standard route Hold short Bravo MAS370.
ATC (12:35:53): MAS 370 Tower.
ATC (12:36:19): (garbled) ... Tower ... (garbled).
Cockpit (no time given): 1188 MAS370 Thank you.
Lumpur Tower (Kuala Lumpur airport runway)
Cockpit (12:36:30): Tower MAS370 morning.
ATC (12:36:38): MAS370 good morning. Lumpur Tower. Holding point.. (garbled)..10 32 Right.
Cockpit (12:36:50): Alfa 10 MAS370.
ATC (12:38:43): 370 line up 32 Right Alfa 10.
Cockpit (no time given): Line up 32 Right Alfa 10 MAS370.
ATC (12:40:38): 370 32 Right cleared for take-off. Good night.
Cockpit (no time given): 32 Right cleared for take-off MAS370. Thank you bye.
Lumpur Approach (Kuala Lumpur area controllers)
Cockpit (12:42:05): Departure Malaysian Three Seven Zero.
ATC (12:42:10): Malaysian Three Seven Zero selamat pagi identified. Climb flight level one eight zero cancel SID turn right direct to IGARI.
Cockpit (12:42:48): Okay level one eight zero direct IGARI Malaysian one err Three Seven Zero.
ATC (12:42:52): Malaysian Three Seven Zero contact Lumpur Radar One Three Two Six good night.
Cockpit (no time given): Night one three two six Malaysian Three Seven Zero.
Lumpur Radar (Malaysia regional controllers)
Cockpit (12:46:51): Lumpur Control Malaysian Three Seven Zero.
ATC (12:46:51): Malaysian Three Seven Zero Lumpur radar good morning climb flight level two five zero.
Cockpit (12:46:54): Morning level two five zero Malaysian Three Seven Zero.
ATC (12:50:06): Malaysian Three Seven Zero climb flight level three five zero.
Cockpit (12:50:09): Flight level three five zero Malaysian Three Seven Zero.
Cockpit (01:01:14): Malaysian Three Seven Zero maintaining level three five zero.
ATC (01:01:19): Malaysian Three Seven Zero.
Cockpit (01:07:55): Malaysian...Three Seven Zero maintaining level three five zero.
ATC (01:08:00): Malaysian Three Seven Zero.
ATC (01:19:24): Malaysian Three Seven Zero contact Ho Chi Minh 120 decimal 9 Good night.
Cockpit (01:19:29): Good Night Malaysian Three Seven Zero.
First published May 1st 2014, 11:06 pm NBCNews
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