As promised, I will respond to some questions that are asked via email by answering here in the Blog.
One of the things I’m most concerned with is the appropriate use of digital processing in transcription for cleanup or remastering of digital archival copies. This includes both questions of when (if at all) processing beyond the actual A/D conversion is appropriate, and which are the techniques and currently available tools best suited to archival audio.
It’s a good question. To some extent, it depends on the client and the final use.
If the restoration/preservation reformatting is for an institutional client, then the first transfers should be as unprocessed as possible — at least the initial copies that are archived should be done that way. The main reason for this is that processing algorithms will always get better and they may hide some information that is useful to future researchers–information that today we consider “noise.”
I am conservative when setting audio levels when making transfers because there is no way of knowing the loudest portion of the signal in advance. So I generally transfer at 24 bits and then raise or normalize the level prior to dithering down to 16 bits for the distribution copy. If I’m working on music, I will generally archive the 88,200 ks/s or 96,000 ks/s files before the normalization.
Processing should generally be done on a copy. The exception to this in my mind are private clients who want the best possible copy of their parents’ wedding, or some other important event. If applied conservatively, noise reduction and equalization will be appreciated by these clients and most of them won’t care a bit that it’s been processed. I keep the unprocessed files on my servers until I am sure the client is happy with the processed version.
As to what to use, there are a wide variety of options available. At the high-end, this falls into the category of “remastering” rather than simple restoration and I’m sure there are options that I’m not aware of.
As a first step, I am very pleased with the basic capabilities built into Samplitude. In addition to that, I use Algorithmix Noise Free Pro as well as the Sound Laundry suite. Really tough projects can often be improved by the filters in Diamond Cut 6 Live/Forensics and most of the filters are available in the lower-priced Diamond Cut 6. Diamond Cut and their main dealer, Tracertek, often run sales which was how I upgraded to Live/Forensics.
Other products with excellent reputations are Cedar Cambridge, Quadriga Audio Cube, and many others. Listening to and discussing with other users via one or more of the mailing lists listed here is very useful.