The Sound of Music: Infrasound and Humans

Have you ever watched that scene from [insert movie or discovery channel] where a bunch of elephants are standing together, going about their normal elephant activities, and then suddenly, they stop and run away together?  When I first saw this scene, I was puzzled as to why this happened.  It was quite strange to see these large but peaceful animals just instantaneously disperse for no good reason.  In actuality, however, the elephants did have a reason for running off.  They responded to a message sent to them by another elephant through infrasound. [1] Elephants are able to detect and send infrasound.  Humans, on the other hand, cannot pick up or produce infrasound the same way elephants can.  For any noise that is between the ranges of 20 to 20,000 Hz, we have no problem audibly hearing these sounds.  Anything that is higher or lower than that range will not be heard by humans.  Infrasound has a frequency that is below 20 Hz and usually, humans cannot detect audible infrasound. [2] However, although we cannot audibly hear infrasound, we are still able to feel the effects of this low frequency.  What are the impacts of infrasound on humans?  And how it is that if we are unable to hear it, it still has an impact on us?
 
Infrasound is found in two forms, it can be ‘man-made’ or created by ‘nature’.  Extreme examples human productions of infrasound include aircraft and fireworks.  The noise from factories and engines also attribute to making these low frequencies. [3] Natural productions of infrasound basically occur all the time.  Weather disasters such as earthquakes, tsunamis, and volcanic eruptions emit infrasound.  Phenomena like meteor impacts and aurora also create this low frequency.  On a less extreme and more relatable scale, anyone who has ever been in a thunderstorm or very strong winds is likely to have experienced infrasound. [3] Instruments can also create these low frequencies.  Organs pipes and bass instruments can produce infrasound as well. [4] As mentioned before, elephants are able to create and detect infrasound.  They are the not the only species who have this trait.  Pigeons, squid and rhinos are just a few among the many other animals who can participate in infrasonic communications. [3] And although many animals can use infrasound to speak, humans still cannot communicate through these low vibrations.

In September 2002, ‘Soundless Music’ was conducted.  The live experiment was designed to see the psychological effects caused by infrasound.  Under a guise of a concert which played electronic sounds and deep bass sounds, an infrasound generator was also incorporated into the mix.  In the questionnaire audiences filled out, many of the responses expressed a strange experience.  Most reactions included anxiety, coldness, and tingling sensations. [3] Many people felt uncomfortable and experienced a deeper sensation of emotions. [5] ‘Soundless Music’ proved to the researchers that infrasound does indeed have an effect on humans, an effect that usually produces negative consequences.

The effects of infrasound are sometimes confused as an experience with the supernatural.  Some people are proposing that organ pipes are the cause for sensations caused by a ‘spiritual’ force (God) in churches and cathedrals. [4] Organ pipes produce infrasound and listening to the organ during a religious ceremony may cause the shivering, increasing heart rates and tingling feelings people experience.  From personal recollection, I get goose bumps when I listen to the organ.  I used to believe that these goose bumps were a result of my amazement by the sound, but now I know that there may be another reason besides just amazement.

Human ears are not made to detect anything that is higher or lower than the range mentioned above.  However, we still detect vibrations from infrasound as seen by the low frequencies that are resonated within the body.  Infrasound raises the pressure in the middle ear, the area where balance is regulated. [6] Exactly why infrasound still impacts us this way was a scientific answer I was unable to find.  An answer that I would like to have is that humans simply evolved away from infrasound.  Perhaps we had the genetics to use infrasound communications but we just did not need it and this trait dissolved with each passing generation.  In contrast to infrasound, ultrasound is the frequency above 20,000 Hz that is also inaudible to humans.  The same middle ear that controls balance also limits the hearing of the high-pitched sounds of ultrasound.  The middle ear is a filter that screens out ultrasound.  If ultrasound were to be sent into the mind without going through the middle ear, it would be heard.  Sometimes even, younger children are able to hear high-pitched noises that older people cannot hear. [7] So if we are able to audibly hear ultrasounds, perhaps at one point in time, humans were able to audibly hear infrasound as well.

Another proposal for why we are able to detect infrasound is because of its affiliation with dangerous weather patterns.  As other animals, such as elephants and birds, are able to detect when a storm is coming, maybe we are given the same trait as well.  But, because we so heavily rely on electronics and mechanical contraptions to tell us what the weather will be like, we do not use our infrasound detection trait. 

I find infrasound to be a fascinating phenomenon.  On some level, it represents many of those things that we cannot see impacting our lives, but it does cause profound experiences.  Infrasound is present in our everyday lives and like many of the other things that affect us, we do not know much about it.  The question that has yet to be answered is still why infrasound affects our bodies and further research should be done to find out.  Hopefully, with more time and research, science will be able to discover a story about infrasound that will answer more questions.

Links:
[1] http://physorg.com/printnews.php?newid=4211
[2] http://arts.guardian.co.uk/print/0,,4669399-110760,00.html
[3] http://spacedog.biz/infrasonic/background.htm
[4] http://newsvote.bbc.co.uk/mpapps/pagetools/print/news.bbc.co.uk/1/hi/sci/tech/3087674.stm
[5] http://icliverpool.icnetwork.co.uk/0300whatson/0800events/tm_headline=soundless-concert-stirs-the-emotions%26method=full%26objectid=12647919%26page=2%26siteid=50061-name_page.html
[6] http://www.forteantimes.com/articles/153_sonicweapons.shtml
[7] http://en.wikipedia.org/wiki/Ultrasound