Get a set of animals with you so that they can (potentially) interact even whilst cloaked/invisible.

From the book, «You Cannot Die: The Incredible Findings of a Century of Death», authored by Ian Currie, the chaptre on hauntings describes a research-investigation being done at a house in Louisiana. Or was it Kentucky ? Or some other state ?

Well, regardless of where the location was, the point is that there was a house that was reported to be haunted, and, one particular room, regardless of the temperature set on the thermometer, was always significantly colder in one corner than the rest of the room...

The researchers brought a dog, a cat, a snake, and a bird, each in their own cage, and, when brought near to the corner of the room, although neither the dog nor the bird reacted, both the snake and the cat got into a defensive attack-stance as-if there was something there in the room-corner...