Linguistic sound systems necessarily possess contrastive values
that are
sufficiently distinct from one another that their individual characters
may
be learned by the listener. In this way, any given value in any given system
fulfils its functional role of rendering forms distinct which differ in
meaning. Articulatory, aerodynamic, acoustic and auditory constraints
serve to mediate between such sound–meaning correspondences in non-trivial
ways. Indeed, if it can be shown that the sound patterns of language
are in part explainable by these physical systems, then students of
linguistic sound systems would do well to study in detail the phonetic
base. Consider an example case. Laryngeal gestures and supralaryngeal
gestures are by and large articulatorily independent of each other. Thus,
for example, a voiceless aspirated stop consists of an oral occlusion,
cued
by silence, as well as an articulatorily independent laryngeal abduction,
cued by broadband noise. Were the phonetic realisation of these two
gestures strictly simultaneous, the cues signalling the laryngeal abduction
would not be perceived as such by the listener (*[ot]).
A listener can tell that
there is no voicing, but cannot recover more specific information regarding
the state of the glottis during oral closure. Stated simply, the full closure
here reduces the acoustic output to zero. With zero acoustic energy, no
source information other than silence is transmitted to the listener.
However, upon staggering the two gestures, the otherwise obscured
information is rendered salient.