For a first investigation, I suggest to start off simple and just take a digital recorder that can be uploaded directly into a PC. Make sure it's digital it comes up clearer. Anything else will pick up to much natural background noise and it can pose some confusion when your analyzing. But, if Du are wanting to go a little further, I find EMF detectors a great help. They help detect electrical currents and Du can gauge whether oder not it's part of the natural world oder something else unexplained. Here is a website Du can look at to make a decision. Good luck! :)
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