Articulation
During the occlusion of the stop, pulling the glottis downward rarefies the air in the vocal tract. The stop is then released. In languages where implosives are particularly salient, this may result in air rushing into the mouth, before flowing out again with the next vowel. (Hence the name "implosive".) However, probably more typically there is no movement of air at all, contrasting with the burst of the pulmonary plosives. This is the case with many of the Kru languages, for example. Note that this means implosives are phonetically sonorants (i.e. not obstruents) as the concept of sonorant is usually defined. However, phonologically implosives can pattern as both, that is they may be phonological sonorants or obstruents depending on the language. Clements (2002) actually proposes that implosives are phonologically neither obstruents nor sonorants, and that they need to be described by the features -obstruent and -sonorant.
The vast majority of implosive consonants are voiced, meaning that the glottis is only partially closed. Because the airflow required for voicing reduces the vacuum being created in the mouth, implosives are easiest to make with a large oral cavity. Thus bilabial is the easiest implosive to pronounce, and also most common around the world. Velar, on the other hand, is quite rare (and uvular even rarer). This is the opposite pattern to the ejective consonants, where it is the velar articulation that is most common, and the bilabial that is rare.
Read more about this topic: Implosives