Through my mulling around on the internet in search for a typical investigative procedures, equipment, etc, I managed to find some very interesting skeptic-based information on infrasound and it's relevance to the paranormal.

What is infrasound? 

The more scientific jargon would be low frequency standing waves, or for the rest of the world, audio frequencies below 20Hz. Humans can naturally detect audio frequencies between 20Hz and 20,000Hz, so it is pertaining to sound that you cannot hear. One might question what this has to do with anything. Here's the scoop. During the middle of the 20 th century, experiments were being conducted on developing weapons based on resonance, or the frequency at which an object will vibrate. 

Does a microwave oven come to mind?

 It uses water's resonant frequency to generate heat through molecular vibration. Through their research, it was determined that body organs vibrated in the infrasonic spectrum, below 20Hz. By manipulating sound, it was believed that they could be used to invoke sickness, incapacitation, possibly death.

Fast forward to current times. In the 1990's, Coventry University Lecturer Vic Tandy was experiencing paranormal activity while working in his laboratory. These included visions, chills, feelings, etc. As a result of his investigation into this phenomenon, he determined that his "ghost" was actually a faulty motor that was emitting a frequency between 17-19Hz. Once the motor was fixed, the phenomenon stopped. After this discovery, he visited various haunted sights in England and found 2 that had high levels of infrasound. In May, 2003, an experiment with infrasound was conducted at the Purcell Room, London by incorporating 17Hz frequencies intermittently into an orchestral concert. Around 700 people attended the two concerts and left surveys questioning their feelings and emotions throughout the event. Their research netted an over 20 percent increase in heightened emotions, anxiety, and chills with the infrasound than without. Low and behold, the scientific realm has finally discounted ghost.....or has it? Out of all the areas that Mr. Tandy visited, he only found two that had infrasonic activity, not all of them. Also, the infrasonic concert doesn't show that any apparitions were viewed that there were times when people felt things when no infrasound was played and vice versa.

What does this mean to the paranormal investigator? 

For one, be aware that it's out there. The more you know about what there is to disprove them is more for you to use to prove them. Second, small scale detection is complex. Most infrasound detection is accomplished by arrays up to 30ft in diameter for detecting subatomic nuclear explosions or incoming space debris. All references I can find relating to small scale detection is related to noise pollution and usually mathematically calculated.

The skeptical community is under the assumption that paranormal investigators and believers will ignore this information, say that ghost cause infrasound, or generally scoff at this groundbreaking evidence of non-existence. There is no need to argue with what they've found, just use it to strengthen our proof that ghosts are there, and that their existence can be proven.