The magnetic field is also displayed.
An essential tool for the aspiring or professional ghost hunter!
Theory of Operation (Only for nerds) ...
It has been reported that paranormal activity is evidenced by sounds inaudible, or barely audible, to the human ear. Animals, whose hearing is more acute at higher frequencies than ours, are able to detect supersonic sounds, generally above 12-15 kiloHertz or so. For example, dogs are reported to behave oddly during supernatural events. Sounds of very low frequency, less than a hundred Hertz or so, are normally felt rather than heard by humans. The built-in microphone circuitry in most handheld devices is designed to detect frequencies in the audio range, but there is some residual response from the circuitry at the very low (subsonic) and very high (supersonic) frequencies.
Ghostroid uses fast software-based Infinite Impulse Response (IIR) filters to measure the level of sub- and super-sonic sound pressure waves arriving at the microphone. It also measures the audible sound level. The three ranges are shown on the Ghostroid display via three meters, which move dynamically and are updated several times a second. The Para Normal Quotient (PNQ) is calculated from a formula that sums the sound levels in the sub- and super- sonic ranges, and subtracts the audible range value. This yields a number which increases as the sub- and super- frequencies (which are difficult or impossible for us to hear) increase, as compared to the audible frequencies.
The PNQ value is shown by a set of concentric bands at the centre of the display. High PNQ values may be caused by a variety of events: Low frequency rumbling (e.g. from heavy trucks or machinery), High frequency noises (e.g. dog whistles, or keys jangling) as well as Supernatural phenomena (please don't drop your Android when you run away in fright!)
Ghostroid is a port to Android of the well-established "Pocket Ghost" application for Windows Mobile. Although I personally remain sceptical about the existence of paranormal activity, and the effectiveness of this application to detect it, I have received several reports over the years of Pocket Ghost being successfully used by paranormal investigators. Here are a couple of quotes:
1) "I have used the pocket ghost program on my I-mate Jasjam and in all cases the Sub-sonic and Super-sonic reading peaked at 85 to 90 and did not drop down until the visions (or what ever they were) had gone."
2) "I have seen your program successfully used by a professional parapsychologist during an investigation in London."
3) "I am a member of several paranormal groups and investigate the most paranormally active sites within the U.K. On one such investigation a parapsychologist was using your 'Pocket Ghost' to great effect."