Infra Sonic Sounds

Infrasonic 17 Hz tone experiment

On May 31, 2003, a team of UK researchers held a mass experiment where they exposed some 700 people to music laced with soft 17 Hz sine waves played at a level described as "near the edge of hearing", produced by an extra-long-stroke subwoofer mounted two-thirds of the way from the end of a seven-meter-long plastic sewer pipe. The experimental concert (entitled Infrasonic) took place in the Purcell Room over the course of two performances, each consisting of four musical pieces. Two of the pieces in each concert had 17 Hz tones played underneath. In the second concert, the pieces that were to carry a 17 Hz undertone were swapped so that test results would not focus on any specific musical piece. The participants were not told which pieces included the low-level 17 Hz near-infrasonic tone. The presence of the tone resulted in a significant number (22%) of respondents reporting anxiety, uneasiness, extreme sorrow, nervous feelings of revulsion or fear, chills down the spine and feelings of pressure on the chest. In presenting the evidence to British Association for the Advancement of Science, Professor Richard Wiseman said, "These results suggest that low frequency sound can cause people to have unusual experiences even though they cannot consciously detect infrasound. 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." (Wikipedia)

(image: http://www.zemos98.org/controlsonoro/2008/03/11/organ-music-instils-religious-feelings/)

It turns out that this infrasonic sound can be produced accidentally by something as harmless as a faulty motor in a ceiling fan, it also happens to be the sound frequency naturally caused by natural disasters like earthquakes, volcanic eruptions, tsunamis and giant animals like rhinos or alligators. All things that we as humans are pretty much hard wired to flee from with an uneasy sense of instinctive weariness or outright fear.  No wonder then that such controversy was bourne by horror film Paranormal Activity when suggestions arose that it was using infrasonic frequencies in the soundtrack. A neat idea, if it weren't that it seems from the reading I have done, quite difficult to make a speaker which will effectively emit infrasonic sounds. Certainly not possible on your regular TV or computer speakers. So there is a lot of buzz around these sounds, people understand that they are a useful tool and it's amazing how much you can freak your self out in an empty telephone factory by downloading an infrasonic sound app!