Voices from the past: the art of audio preservation

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Keeping it reel!

For the last year I have been digitising audio as part of Unlocking Our Sound Heritage.

Our team at National Museums NI is one of 10 regional hubs working all across the UK to preserve sound recordings that tell the unique history of each region through music, radio, drama, poetry, oral histories and everything in between. This ambitious nationwide project, led by the British Library and funded by the National Lottery Heritage Fund, aims to digitally preserve almost half a million rare and at-risk sound recordings.

Over three years at National Museums NI, we aim to digitise and catalogue 5,000 recordings from our own collection and the collections of our partners across Northern Ireland including from organisations such as PRONI, QUB, Larne Museum, Somme Museum, Glens of Antrim Historical Society and Manx National Heritage.

At risk and urgent!

These recordings are currently held on obsolete mediums such as cassettes and open reel tapes which are physically degrading. General consensus between audio archivists is that we have around 15 years before unique recordings like these are irretrievably lost.

Our own audio archive is a real treasure trove of material, reflecting the work of museum staff and the work of other groups and individuals. Recordings relate to folklore, crafts, language, industry, transport, music and song.

Image: National Museum NI’s Audio Archive © Amy Hamill
National Museum NI’s Audio Archive © Amy Hamill

As I said earlier, our aim is to digitise 5000 at risk sound items in 3 years. At the time of writing, I have currently preserved over 1700 items, so I am well on the way to reaching my target.

The vast majority of these items have been on magnetic tape, both open reel tape, and compact cassette, which if you are of a similar vintage to myself you might be familiar with. Open reel tape in the archive has mostly been a pleasure to work with. A lot of the tapes that I have worked on so far have spent the majority of their lives in a temperature and humidity controlled vault in our audio archive.

Image: Studer A810’s open reel tape machines © Jonny McBride
Studer A810’s open reel tape machines © Jonny McBride

That being said, a lot of open reel tapes in our archive are of a particular brand that suffers from Sticky Tape Syndrome. This is where the adhesive that binds the oxide coating to the plastic backing of the tape breaks down and the oxide sheds off when playing the tape in the replay machine.

My job involves baking… who knew!?

Without intervention Sticky Tape Syndrome results in permanent damage to the tape and unwanted audio characteristics on the transfer. The way to resolve this particular issue is to ‘bake the tape’ more accurately known as treating the tape in an incubator. This cures the adhesive for up to 4 weeks. After this period of time the adhesive breaks down again and the baking process would need to be repeated to play back the tape.

Image: Tape preparation in “the oven” © Jonny McBride
Tape preparation in “the oven” © Jonny McBride

“Make it sound better”? Definitely not!

My role involves taking the “at risk” analogue format and creating a preservation copy from that. As it is a preservation copy I do not change or try to enhance it in any way to make it sound good, as making something sound good is subjective.  Being true to the original recording is of utmost importance.

In saying this, there are still things to be done to make sure that the preservation copy is optimised so as to get the best out of the original audio. Replay tape heads need to be cleaned and free from any dirt, degaussed and aligned to match the angle between the original record head and the tape.

Tapes are grouped and digitised on the same machine to ensure that there is a consistent level and sound for the listener on playback.

I use analytical tools to visually represent and make sure that the original material is optimised, but critical listening skills are very much needed for setting analogue equipment and getting the best possible transfer.

Image: Analytical tools looking at frequency content and phase © Jonny McBride
Analytical tools looking at frequency content and phase © Jonny McBride

Future proof!

Aside from the digitisation process there is a lot of technical metadata that needs to be preserved and bundled with the audio file so that people in the future are aware of our working process and of the original carrier information.

Next steps…

For the first year of the project we have been focused on recordings from our own collections. Now as we move into year two, we will begin preservation work on the material from these partner organisations - an exciting new chapter for the team.