One of the effects of SHD (Selective Hearing Disorder) is that certain sound waves are unable to penetrate the ear as this aural engineer proves on tests carried out on this artificial recreation of the right ear of ex-Bon Accord batsman, Kami Malik.

Often mistaken as a by product of cheating, subliminal edges are, in fact, the result of an innumerable amount of factors, variants and combinations of elements, that continue to be a source of controversy and aggravation, in the world of Grades cricket.

A subliminal edge is, in most respects, identical to an actual edge (an edge being when a batsman makes contact with the ball with the outer edges of the cricket bat). However, whereas an actual edge may make a sound or force a deviation in the path of the ball and be observed by both players and umpire, a subliminal edge (although, in every other respect, the same as an actual edge) is only clear to the fielding side, most of the watching support and the striking batsman. The umpire and, in many cases, the non-striking batsman are oblivious to any discernible edge.

Possible causes of subliminal edges

Sound transference

Many instances of subliminal edging can be put down to sound transference, or rather, lack of it. A strong wind blowing from behind an umpire may inhibit sound waves caused by an edge. From the opposite perspective, these sound waves might sound like a clap of thunder, by comparison.

SHD

Many Grades batsman suffer from periodic bouts of Selective Hearing Disorder (SHD). There are many possible triggers for SHD. Loss of confidence, or form, general  bad sportsmanship and the state of any particular game, at any given time, can instigate an instance of SHD. Subliminal edges, in these circumstances, however, would require a similarly affected umpire to be in place and although, it has been known to happen, SHD is the least probable cause.

Insect interference

The two possible causes, as described above, are dependant on sounds going unheard. However, in many subliminal edge situations, audible sounds may be created, not by bat on ball, but by bat striking an insect, most probably a fly or midge. It has, to date, been difficult to provide any empirical evidence (insect tissue on the bat, or visual confirmation of collision) to support this hypothesis, although it is generally regarded as plausible. 

New theories

The latest developments in cricket technology have been suggested as possible causes for subliminal edges. Silent bats are the most obvious of these. It should be noted, however, that although the effect of an edge made subliminally, or by a silent bat, is, in many ways, the same, the silent bat technology is designed, specifically, to recreate (what amounts to) subliminal edges.