3 elements in an audio digitisation workflow that will really impact quality.
Recorded sound collections exist everywhere: oral histories, speeches, concerts, music, language collections, interviews, music and so much more. They are held at universities, schools, corporations, archives, libraries and a plethora of other repositories. With the growing demand for using and sharing historical audio material, as well as the knowledge that collections are at risk due to degradation and technical issues, many collection custodians are moving to digitise their audio content.
For most organisations, an investment in digitisation means taking scarce financial resources from other business areas. As such, custodians need to feel 100% confident that this investment in digitisation delivers high-quality results, and that corners are not cut in the process, leaving the sound quality compromised.
As with many things, the outputs of digitising audio can deliver varying results depending on the process and expertise used. To help you understand what components of the audio digitation process will impact the quality of your final result, we have identified three factors that will influence the quality of the digital file.
Quality of Playback Machines and Signal Path
Quality of the playback machines and Analogue to Digital converters, digital audio interface and recording encoding software all play a critical role in optimum audio digitisation. IASA TC-04 standard provides a guideline and technical recommendations for playback machines and analogue to digital conversion. Equally important is high quality cabling between devices, as well as proper audio ground management and mains earth, so as not to introduce hum.
In addition to the using the appropriate quality of processing equipment, high-end monitor speakers should be used in the process. These should be ‘neutral’ – nothing which would colour the audio to make it sound “pretty”, we need to hear all the hissy top end while watching phase meters for accurate azimuth (the angle of the tape head on the tape itself) adjustment!
At the foundation of a successful audio digitisation project will be the right equipment guided by international standards.
Poorly Prepared Physical Media
Some audio cassettes and reels might not have seen a playback device for years, even decades. And not all media will have been treated with the love and respect that it deserves. That’s why proper inspection is a must before any playback attempt it made, to protect against damaging the item, or damaging the obsolete playback technology.
Physical repair work might be required and this is a science unto itself. Tapes that have been stored with a poor tape pack can be damaged beyond repair if they are not treated correctly before digitisation, as can tapes exhibiting common forms of degradation like mould, Sticky Shed Syndrome and Soft Binder Syndrome (see our previous post).
Exercising of cassettes and reels can greatly improve quality of playback; however, this process can be very detrimental if the media is fragile. That’s why an experienced audio engineer is the best person to make such decisions.
It’s important that media isn’t just put in a deck and played, as damage can ensue and in extreme cases you might only get one chance to capture the content before it completely dies. The ability to properly identify media with condition issues is critical as it will affect the quality of the digitised file. Even more important is that identified problems are handled correctly and that any risks to the media are raised before the digitisation proceeds.
Improper Signal Processing of Preservation Masters
The preservation master should be just that – a preservation master. What this means is that the digital file created should be the most accurate and true representation of the source material possible, and should not pass through any processes which might alter the signal. In other words, the master should be warts and all.
To achieve this, the processes should be transparent and pass the signal unaltered at every stage; from replay machine, including on-board amplifiers, A/D converters, interface, encoding software. Unfortunately, in today’s marketplace, there are many “pro-sumer” products available, both hardware and software, which have in-built processing of which end users may be unaware.
A professionally designed suite, using industry grade hardware and software, ensures that operators are in full control of the signal path and can ensure end-to-end integrity of the digitised content.
Once you are delivered the preservation master, warts and all, you can then create derivatives that can be digitally restored. But you always want to get that preservation master so you have a like-for-like copy of the original content.
It’s important to recognise that there are a range of factors in the digitisation process that will affect the quality of your digitised audio. With this in mind, you will be better informed for your conversation with your digitisation partner (internal or external) as you start to migrate your content from physical to digital.
Our recommendation is for you to look at the IASA TC-04 standard and use this as a guide. And then make sure your digital partner delivers their audiovisual digitisation services in line with the standard as outlined. This goes a long way to guaranteeing the quality of your audio digitisation project will be of the highest quality and secure the integrity of your valuable collection into the future.