West Coast Ghost and Paranormal Society

The human ear is capable of hearing many of the sounds produced in nature, but certainly not all.  Some low frequencies like a heart beat of one or two Hz can not be heard, just like sonar sounds produced by dolphins are too high.  Any frequency that is below the human range is known as infrasound.  It is so low that it may only be detected by a creature with big ears, such as an Elephant.  In fact, recent research indicates that elephants also communicate with infrasound.  Ultrasound, on the other hand, is above the range of the human ear.  Bats, whales, porpoises, and dolphins use ultrasound for navigation.  Most bats can detect frequencies as high as 100,000 Hz.

The number of vibrations that are produced per second is called “frequency”.  Frequency varies for each sound and is measured in “hertz”.  One hertz is equal to one vibration per second.  A sound with a low frequency will have a low pitch, such as a human’s heartbeat.  A sound with a high frequency will have a high pitch, such as a dog whistle.  Humans cannot hear sounds of every frequency. The range of hearing for a healthy young person is 20 to 20,000 hertz. The hearing range of humans gets worse with age. People lose the ability to hear sounds of high frequency as they get older. The highest frequency a normal middle-aged adult can hear is only 12-14 kilohertz.  Also, the hearing range for men worsens more quickly than the hearing range for women.  This means women will have the ability to hear notes of higher pitch than men of the same age.

White noise is a type of noise that is produced by combining sounds of all different frequencies together.  If you took all of the imaginable tones a human can hear and combined them together, you would have white noise.  The adjective “white” is used to describe this type of noise because of the way white light works.  White light is light that is made up of all of the different colors (frequencies) of light combined together (a prism or a rainbow separates white light back into its component colors).  In the same way, white noise is a combination of all of the different frequencies of sound.  You can think of white noise as 20,000 tones all playing at the same time.

Because white noise contains all frequencies, it is frequently used to mask other sounds.  If you are in a hotel and voices from the room next-door are leaking into your room, you might turn on a fan to drown out the voices.  The fan produces a good approximation of white noise.  “White noise” is characterized by the fact its value at any two different moments in time are uncorrelated.  This leads to such noise having a flat power spectral density (in signal power per hertz of bandwidth), and is loosely analogous to “white light” which has a flat power spectral density with respect to wavelength.

Pink noise has flat power spectral density per percentage of bandwidth, which leads to a roll off of -3 dB/octave compared with white noise.  There are many reasons for using pink noise in audio testing.  One is that music has an average spectral content much closer to pink noise than white noise.  Another is that pink noise can be readily measured with constant Q bandpass filters and naturally leads to flat plots on logarithmic frequency scales – which correspond to the equally tempered musical scale.

Pink noise is often used with 1/3 octave band filters to measure room acoustics.  This idea has merit since 1/3 octave is a convenient number near the limit of our ears ability to detect frequency response irregularities, and because averaging measurements over 1/3 octave bands smooths out the numerous very narrow peaks and dips that arise due to standing waves in rooms.

When reviewing audio evidence (especially when a number of people are present and there is the constant presence of wild life and bugs), it is often easy to think that someone in your party who is away from the recorder is an EVP.  The structure of a building (building materials, the age of the building etc.) must also be taken into consideration.  For instance, wood floors are always going to be susceptible to weather or humidity changes.  Likewise for the wood framing of any structure.  As temperature or humidity changes, the wood will expand or contract and cause all sorts of strange noise which can be mistaken for paranormal activity.  Doors may even open and close by themselves due to these changes.

Buildings without carpeting will have issues with sound waves bouncing freely through the structure, as carpeting absorbs sound waves where wood and cement do not.   A sound far away may appear closer than it actually is.  The sound may actually be altered from its original due to reverberation or an echo effect in structures like these. 

Why do people report certain events as paranormal?  Most such reports, when properly investigated, turn out to be normal phenomena.  At this point in a case, many paranormal researchers tend to lose interest as they are looking for the genuinely paranormal.  The problem with this is that many of these often rare, natural phenomena resembling the paranormal are never properly researched.  This means when such events occur again, researchers may have to relearn everything others have already found out.

It would be helpful if there were a term for events that, in certain circumstances, resemble the paranormal, even though they are not.  They could be called ‘xenonormal’, meaning ‘foreign normal’; in other words ‘the unfamiliar but natural’.  In many cases, witnesses to apparent paranormal events (and sometimes even the researchers!) are simply unfamiliar with a purely natural phenomenon.

The xenonormal covers not only rare, exotic phenomena but also some common ones simply unfamiliar to particular witnesses.  If someone hears odd noises in their house that they cannot explain, they might report it as a ghost even though a plumber would know what is was immediately.  Similarly, a witness unfamiliar with the planet Venus might report it as a UFO, where an astronomer would never do so.