Video: The Noisy Ghost

The Poltergeist, or “noisy ghost” is an unexplainable phenomenon by
which a seemingly intelligent entity manifests, showing its presence
through a series of sounds (often knocking) and often moving objects
around the room.  Often poltergeists are thought to be the
manifestation of repressed emotional energy, but this hasn’t been
demonstrated conclusively.

Poltergeists often are said to be
mischievous and play pranks on those who are living around them. 
Skeptics assume poltergeist activity is largely a natural phenomenon,
the result of tremors or the sudden loss of gravity which has yet to be
explained.  Since these claims are often as strange as the paranormal
explanation, there are few who can venture toward a conclusion armed
with more than pure speculation.  The phenomenon is reported in the
United States, India, the UK, Japan, Brazil, Germany, Spain, Chile, and
a host of other countries.  And those who don’t believe may change
their mind when reading the plethora of cases that have reached the
public eye in the past hundred years.

Take Greyfriar’s
Churchyard for example.  Since 1998, spirits have been reported
violently attacking those who enter it.  In 2006 alone, over 500
visitors reported being clawed at, bitten, or knocked unconscious by a
strange unseen force within the area.  The most haunted location within
the Churchyard is supposedly near George MacKenzie’s Black Mausoleum. 
It is also one of the few locations that have been responsible for the
death of a man attempting to exorcise it.  During the ceremony he had
to stop, and one week later he died of heart attack.  Needless to say,
poltergeists are not something to be trifled with.

the other hand, many poltergeists appear quite happy to simply cause
some small amount of mischief and leave the occupants of the homes and
places of business they haunt to go about their daily lives in peace. 
Of course there are other cases, as exampled in this video from
youtube.  If genuine, it does show a perfect example of how
poltergeists seem to work.  Though this is a surveillance video and
there is no clear sound, you can tell that it is sound that is alerting
the store clerk to each videotape as it drops.  And even the movement
of the cart no doubt created some sort of sound that ultimately caused
him to look up.  If this is, however, no more than a hoax then it still
serves as a dramatic recreation of how a poltergeist is commonly
reported as behaving.  Other activities poltergeists commonly engage in
are scrambling radio reception so that a crisp song can come out as a
scrambled garbled mess of static and strange otherworldly words.  Some
have reported poltergeists actually attempting to communicate with them
through the radio, telling them who they are, what their names were, or
who they were.  Of course many stories indicate that these
communications are often entirely fabricated.  So what are
poltergeists?  Are they the spirits of the dead?  Or are they simply
emotional energy given a sort of spectral consciousness and energy
without form, whose only purpose is to propagate chaos?