I've never had much luck with ghostly voice recordings. Nothing to shout about anyway, nothing I could prove wasn't just me with a sore throat. Still, I keep refining the techniques and keep trying. One day a ghost will say something verifiable on tape and when they do, I want to be able to hear it.
First of all, recorders:
The somewhat lousy photo shows a standard cassette recorder and a digital voice recorder. The digital has many advantages, not least its size and its much smaller battery. With the full size cassette you need to carry spare 'C' cells in packs of four. The digital recorder uses one 'AAA' cell. So, less weight and bulk of recorder and less weight and bulk of spare batteries. An all-round winner so far.
Sound quality on the digital sounds, to my untrained ear, much the same as the cassette but without the tape hiss and motor rumble. Better, in other words, maybe not clearer but with less interference. Lastly, it's easy to transfer the sound files from the digital recorder to a computer.
That ease of transfer is a flaw. Once on a computer, a sound file is easily doctored. There's no 'original tape' to hold up as evidence. Although the digital file is date-stamped while the tape isn't, date stamps can be faked too. However, the sceptics are likely to claim the tape was faked anyway so there's really no advantage in having it these days. What we need is speech, saying something that can be verified, and that nobody else could know. Where Great-Uncle Wyndham buried his box of button badges, something like that. Of course, if he tells you where he buried a ton of gold, you then have to decide whether you want to go public on that.
The other problem you might come across with digital recorders is that many don't have a socket for an external microphone. The one pictured does, but the first one I bought didn't. All these recorders come with internal microphones that are perfectly good for normal use, but we're not talking about normal use. We're talking about faint and often indistinct voices. So an external microphone, a good one, is a must. It doesn't have to be studio quality, just clear and safe from noise sources.
I prefer these. Designed for computer use, they aren't expensive and they come with a base so they're held off any surface you place them on. Not vibration-proof but with a foam pad under them, they're pretty good. They don't weigh much either - remember, if you're going to cart a load of equipment to off-road locations, you want it all as small and light as possible. Also cheap, because you inevitably lose bits now and then.
The mics above are directional, in that they pick up most effectively from the area directly in front of them. A boundary microphone picks up sound from all around, and looks like this:
It's a good idea to have one of these, I think. I haven't tested this yet. It's new. Oh, and keep a few of those plastic-coated wire twist ties handy. Otherwise you'll be untangling cables all night.
To summarise all that rambling, go for digital over tape recorders because they're much smaller and lighter and so are the spare batteries you need. Digital recordings are free of tape hiss and rumbles and easily transferred. The only advantage of tape is having that original recording but since you'll inevitably be accused of faking it anyway, it's not enough of an advantage to be worthwhile.
Get some external microphones. They're always better than the built-in ones.
Finally, since these are the first photos from the new lab, here's another look. I'll take more photos when it's fully equipped, and after the sacks of decorating waste are gone, but that ghastly carpet is out, tiles are laid and the walls are painted. It looks like a lab, rather than a dilapidated shed now. All it needs is an espresso machine, and that's in the back of the car ready to go in tomorrow.
Well, I have to have the essentials...