Friday, October 29, 2010

Infrasound and Otoacoustic Emission

I was reading about two very interesting auditory phenomenon. The first is called infrasound and is defined as a low frequency now below 20Hz. The other is called otoacoustic emission and is a noise produced by the inner ear in the absence of external stimuli. You can just click the links and learn exactly as much as I know on each subject but let me summarize for you.

As I said, infrasounds are low frequency noises below 20Hz. They are frequently generated by very large objects or natural disasters. Most animals are sensitive to these frequencies which explains why animals can detect impending earthquakes. Animals such as whales also use these frequencies for communications. Humans can hear as low as 20Hz, but can perceive lower frequencies is the amplitude of the wave is high enough. 

These sounds are interesting because they are said to be the cause of perceived paranormal activity. According to studies, frequencies at about 19Hz can give the feeling of dread and paranoia. Also if the frequency is loud enough, it can cause resonation with the eye which can smear vision which would explain shadowy figures. I'm not saying this is the whole story, but it is interesting nonetheless.

From the page on infrasound I came across the otoacoustic emission page. I thought this was interesting because it was remarked that 30% of people can hear these noises (frequently heard as a ringing) and I am definitely one of those people. I always thought it was strange when I would randomly hear a noise that definitely wasn't there, but I dismissed being crazy because I could feel it (so I wasn't making it up). Now I know that phenomenon is true, and reading about it is pretty interesting. 

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