Natural background noise or messages from the other side?Williamson, a 47-year-old former cleaner, is a dedicated collector of "electronic voice phenomena", commonly known as EVP - the mysterious voices or voice-like sounds, often distorted amid other extraneous noise, which can crop up on tape recordings, broadcasts, even telephone answering machines. Some believe these are communications from the afterlife, others that they are simply random noise from electromagnetic or other earthly sources, in which believers simply hear whatever they want to hear. However you may interpret it, and even if you haven’t heard of it up until now, EVP will have a much higher - and scarier - profile from 7 January when the film White Noise is released, starring Michael Keaton as an architect who becomes obsessed with EVP following the disappearance of his wife. So far as Williamson is concerned, however, there is nothing scary about EVP, although her introduction to the phenomena was unsettling enough. In 1998, she and her friend, Irene MacIntyre, were working as early-morning contract cleaners in a factory on Dundee’s dockside, when a rash of odd occurrences - such as things being moved about and doors being slammed in their faces - prompted Williamson to bring in a cassette recorder, which she left running while she was working. She plays me an extract from that first tape, now stored along with hundreds of other EVP on her computer: there is a noise of what sounds like furniture being banged about, and of women laughing.