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How do you Authenticate Reel to Reel Audio Tape?

reel to reel authentication

One of the activities performed in a forensic audio laboratory is a reel to reel tape authentication and analysis test. This is the scientific process of determining the authenticity and integrity of a reel to reel recording. Although reel to reel tape recorders are not used today as much as they were prior to the year 2000, reel to reel tape evidence authentication testing is still a relevant forensic activity. Experts at Primeau Forensics still receive the occasional reel to reel tape as evidence in a court case. Mostly, these tapes have either surfaced and will be used for an appeal or they were evidence in a trial and are not thought to have been altered or tampered with.

As an audio forensic lab, we do not see much analog (reel to reel) tape evidence these days. When we do, based on our training and experience, we take several steps to authenticate and analyze these analog recordings. It is important to perform tests which first show if the recording is an original. It is a common practice and easy process to create a seamless edit on a reel to reel tape to remove or add content. Once the editing is complete, that tape is then transferred to another tape and a copy is created. A copy that does not have visible splices.  

When editing occurs, a trained audio forensic expert can detect these edits while critically listening to the recording. Changes in the background noise floor are observed and noted. Think of edit detection this way. If we had a conversation that was recorded on reel to reel tape while music was playing in the background. If somebody decided to remove a portion of the conversation by editing the recording, while listening critically, you can hear a jump in the music. The same is true with other background sounds like room tone or ambiance and HVAC motors and appliances.

Reel to Reel Editing

When editing a reel to reel tape, there are four components. First, a reel to reel tape recorder, a single edge razor blade, an edit block, and splice tape to reassemble the tape after editing.

When playing a reel to reel tape, the transport pulls the tape through the head configuration from the left reel to the right reel. The tape path pulls the tape across three tape heads. The first head on the left is the erase head. Its job is to remove any previous sound that was recorded on the tape. The second or middle head is the recording head. Its job is to pass the signal or dialogue onto the magnetic tape where the sound is stored. Head number three, the one on the right is the playback head which is responsible for playing the sound stored on the magnetic tape. 

An editor or tape operator uses a grease pencil while listening to the playback and marks where the words begin that are to be removed. Then, the editor places a second mark at the end of the dialogue to be removed. Next, a single edge razor blade is used to physically cut the tape at each grease pencil location. Using the splice block to remove the unwanted section, an editor reassembles the two sections of tape by applying splice tape to connect the two sections of tape back together minus the portion that was removed.

Case Studies-Reel to Reel Tape Authentication and Analysis

Perhaps the most famous reel to reel tape authentication and analysis testing was conducted in 1974 by a group of pioneers in audio forensics. They were tasked with forensic authentication and analysis of the 18-minute gap in a White House recording. There is only one way to remove content from a reel to reel recording, physically remove it from the reel of tape using a razor blade, edit block, and splice tape. In order for the edits to be hidden as much as possible, cuts are made in very strategic locations in the dialogue. The original tape is then transferred to another tape which is then labeled as the original.

On November 22, 1963, John F Kennedy was assassinated in Dallas, Texas. The plane used as transportation for Mr. Kennedy and his wife and staff was Air Force One. They arrived in Dallas at 11:37 am that day. Air Force One then left Dallas and was in flight over the Pacific Ocean when the news came through via radio transmission. Mr. Kennedy had been fatally shot. This radio transmission continued until the plane returned to Andrews Air Force Base and was recorded onto reel to reel tape. Forty-nine years later, I was contacted by Duquesne University and asked to participate in restoring and assembling two versions of these reel to reel recordings of the radio transmissions that day.

During my assignment to assemble two versions of the Air Force One Recording Transmissions the day JFK was assassinated; I could hear what I interpret as edits. Interruptions in the background noise floor abrupt changes in overall sound tone and quality from one moment in the recording to another. These deviations are also known as anomalies which are potentially edits. I know firsthand that the Air Force One recordings have been edited because I personally worked on assembling two different versions of the transmissions. The existence of two versions of the transmissions tells me that there is another version, the original, that has still not surfaced. For two versions to exist, that means one original had to be played from one reel to reel to another reel to reel to make each version that I was provided. Some of the overall dialogue was included in one version of the recording, the LBJ Library version which was released in the early 1970s. Additional and different dialogue can be heard in the second version that was discovered in the estate of General Clifton around 2011 after he died.

I would conclude, based on scientific fact, that the Air Force One recordings did not pass reel to reel tape authentication and analysis testing because of the anomalies I experienced.  

The average shelf life of analog reel to reel tape is 25 years when stored properly in climate-controlled conditions. To restore poor quality reel to reel recordings for tape authentication and analysis testing, an audio forensic expert may forensically enhance the recording for better intelligibility during the critical listening phase. Audio forensic experts use a variety of filters like a high pass filter to remove low end rumbling. A low pass filter can be set at the appropriate frequency to remove tape hiss allowing for the dialogue and background noise to be more intelligible.

If the original equipment is available that created the recording, it is tested and compared to the machine signature of the evidence recording. A forensic expert creates a control recording or exemplary recording. This is a sample recording created using the same equipment as the evidence recording. Nondestructive fluid, Kyread Fluid, is applied to the oxide side of the tape to develop the machine signature in the magnetic coating of oxide. The machine signatures of both recordings then undergo comparative analysis.

Even if the original recorder is not available for testing, and exemplar is not created. However, the same process can be used when different sounding sections in the evidence reel to reel recording are present. For example, if the dialogue sounds different in one portion of the recording then the other, the same testing procedure using Kyread Fluid is executed on the two different sounding sections in the evidence recording. If the machine signature looks different, this is an indication that the tapes were crested on two different types of recorders or that a portion of the recording is a copy while the other is an original.

With the proper process in place, reel to reel evidence recordings can be forensically authenticated and analyzed for integrity and accuracy. If you have an analog reel to reel tape that requires forensic authentication and analysis testing, call our Rochester Hills, Michigan lab and speak to me, Ed Primeau. I have been analyzing and testing reel to reel recordings for 35 years. I am happy to answer any questions you have about reel to reel tape authentication and analysis.

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