This presents some interesting considerations for ghost researchers. To accurately substantiate the difference between ghost activity and natural phenomenon many traditional devices are rendered useless. Sound recordings, while helpful for documenting the occurrence, do not prove anything other than the fact that something was heard and that it did not come from living human sources or from atmospheric sources as typically noted (traffic, wind in the trees, machinery)but does not rule out spatial echoes in the aquifer. Additionally, since limestone is active in electromagnetic field propagation, the standard or even advanced EMF detectors commonly used in the field must be discounted as well, as EMF would be considered a ‘normal’ reading on sites which are rich in limestone.
Before attempting to theorize on a site of this nature, it is advisable to check the geology of the area. An overall knowledge of what sediments are found locally is imperative, and if the area is found to be relatively rich in limestone it would be prudent for the thorough researcher to acquire the specific geological data on the exact property in question, as well as any immediately nearby properties to assess if any changes in the bedrock or near bedrock could have increased water absorbency or plate movement. A thorough study of atmospheric condition (including relative humidity) for the dates and times of the sound reports should also be included in case notes.
Please note that the limestone plates need not be large. Even some as small as a dinner plate, when moved with force against another of the same size, will give off a discernible sound. Sensitive ears may hear every movement. As an interesting aside, a similar occurrence happens in mass graves that are thousands of years old the bones degenerate into limestone deposits which could conceivably generate the same phenomenon with sound.
Further Reading And Study:
A quantitative appraisal of airborne and ground-based transient electromagnetic (TEM) measurements in Denmark:
A large selection of links on geological, seismic and radial studies is available here