A ghost is usually defined as the apparition of a deceased person, which frequently carries the deceased person's likeness and is experienced in association with the person's former habitats.

The word "Ghost" may also refer to the spirit or soul of a deceased person, or to any spirit or demon Ghosts are often associated with haunting, which according to the Parapsychological Association is
"The more or less regular occurrence of paranormal phenomena associated with a particular locality (especially a building) and usually attributed to the activities of a discarnate entity;cold drafts, sounds of steps and voices, and various odors."

Ghosts are scientifically controversial phenomena. Many people believe they are real spirits of the deceased, while others believe ghosts are supernatural .

scientific analysis :
Sound waves with frequencies lower than 20 hertz are called infrasound and are normally inaudible, but British scientists Richard Lord and Richard Wiseman have concluded that infrasound can cause humans to feel a "presence" in the room, or unexplained feelings of anxiety or dread.