Radicals are sounds produced in the back of the throat. They are divided into two categories: pharyngeals and epiglottals. Pharyngeals/epiglottals are commonly found in North Africa/Middle East (Arabic and related languages) and in British Columbia, in the Salishan languages. Pharyngeal plosives are thought to be impossible. Very few languages contrast epiglottal and pharyngeal consonants.
The pharyngeals possible are the voiceless pharyngeal fricative and the voiced pharyngeal fricative, actually an approximant. The epiglottals possible are the epiglottal plosive, the voiceless epiglottal fricative, the voiced epiglottal fricative, actually an approximant, the epiglottal trill, and the epiglottal flap, which is not known to occur in any language.
The click consonants
Click consonants are consonants that do not require air coming up from the lungs or glottis. As such, they cannot be voiced. The air steam they use is ingressive, pulling air in with the tongue. The most common click sound familiar to speakers of English is the 'tsk tsk' sound used to signal disapproval. which is a dental click transcribed [||].
They are very rare, but several languages of southern Africa use them.
Click consonants are famous to the Western world mainly because of the 1980s movie, The Gods Must Be Crazy. And a singer who used them heavily in her songs, drawing on their exotic sound.
An Ingressive airstream is what is generated when, instead of breathing out, you breath in. Ingressive consonants are voiced, note that an unvoiced ingressive stop is a click. I myself cannot produce a creaky ingressive, but that is not to say it is impossible. All of the egressive stops have an ingressive analogue.
- b - ɓ
- d -ɗ
- ɟ - ʄ
- g - ɠ