NPL subjective testWhen it comes to claims about hauntings, religious awe and beam weapons, people can be highly suggestible.

In our Purcell Room experiment, we worked hard to overcome the effects of suggestion – by creating a ‘blind’ test of infrasound in two counterbalanced events (see previous pages).

In a recent art installation, an associate borrowed one of my infrasound generators and put it on display – with a label warning visitors about its ‘powers’ – but did not switch it on. Despite the lack of infrasound, wary visitors complained of a number of strange effects when they went near the generator, including anxiety. One of them asked the exhibitor to switch it off.