By Patricia Reaney
MANCHESTER, England (Reuters) - Mysteriously snuffed out candles, weird sensations and shivers down the spine may not be due to the presence of ghosts in haunted houses but to very low frequency sound that is inaudible to humans.
British scientists have shown in a controlled experiment
that the extreme bass sound known as infrasound produces a
range of bizarre effects in people including anxiety, extreme
sorrow and chills -- supporting popular suggestions of a link
between infrasound and strange sensations.
"Normally you can't hear it," Dr Richard Lord, an acoustic
scientist at the National Physical Laboratory in England who
worked on the project, said Monday.
Lord and his colleagues, who produced infrasound with a
seven meter (yard) pipe and tested its impact on 750 people at
a concert, said infrasound is also generated by natural
phenomena.
"Some scientists have suggested that this level of sound
may be present at some allegedly haunted sites and so cause
people to have odd sensations that they attribute to a ghost --
our findings support these ideas," said Professor Richard
Wiseman, a psychologist at the University of Hertfordshire in
southern England.
In the first controlled experiment of infrasound, Lord and
Wiseman played four contemporary pieces of live music,
including some laced with infrasound, at a London concert hall
and asked the audience to describe their reactions to the
music.
The audience did not know which pieces included infrasound
but 22 percent reported more unusual experiences when it was
present in the music.
Their unusual experiences included feeling uneasy or
sorrowful, getting chills down the spine or nervous feelings of
revulsion or fear.
"These results suggest that low frequency sound can cause
people to have unusual experiences even though they cannot
consciously detect infrasound," said Wiseman, who presented his
findings to the British Association science conference.
Infrasound is also produced by storms, seasonal winds and
weather patterns and some types of earthquakes (news - web sites). Animals such as
elephants also use infrasound to communicate over long
distances or as weapons to repel foes.
"So much has been said about infrasound -- it's been
associated with just about everything from beam weapons to bad
driving. It's wonderful to be able to examine the evidence,"
said Sarah Angliss, a composer and engineer who worked on the
project.