The activity of the vocal cords/folds : The vocal cords may or may not be activated/ vibrated by the expelled air. The sounds, accordingly, fall into the categories of either voiced or voiceless.
Phonation : the use of the larynx, aided by an airstream, to generate an audible source of acoustic energy that can be modified by the rest of the vocal tract. Phonation is the contribution the larynx makes to speech. It is important to bear in mind that besides the role involving the vibration of the vocal folds as a sound source, the larynx has two other functions in speech: it can generate an airstream (yielding glottalic consonants) and it can serve as an articulator (in glottal consonants).
Phonation type (also: phonatory /

/ stricture type): any of the various distinguishable types of activity in the glottis which can produce a stream of air for the organs of articulation. There is some disagreement as to which types should be recognised. Simple phonation types include:

NIL PHONATION
: It means silent voiceless flow of air through the glottis, at volume-velocities below about 200—300 cm³/sec (see Fig. 3 on page 3). It can also called voiceless phonation, which means the absence of any phonation.
The vocal folds/cords are held far enough apart to allow a laminar (nonturbulent) airflow through the glottis. The opening between the vocal folds for voiceless articulation is similar to that required in normal breathing.

BREATHY VOICE or MURMUR : It involves turbulent, noisy flow of air through the open glottis, typically at volume-velocities above about 200—300 cm³/sec. It is produced with very low muscular tension in the larynx. The vocal folds vibrate but do not meet completely, and the rate of air flow is therefore high, producing a ‘breathy’ or ‘sighing’ voice quality. Breathy voice is not known to be used contrastively in languages (except for several languages of South Asia) but is characteristic of some individuals on some occasions.

WHISPER : It is a simple phonation type characterised by complete closure of the anterior (ligamental /

/) part of the glottis combined with a broad triangular opening in the posterior (arytenoidal /

/) part. Air flowing through the opening produces significant turbulence and hence the distinctive "whisper" sound quality (see Fig. 5 on page 3). As the area of glottal opening is small, this mode can provide turbulence with relatively low airflow rates (from about 25 cm³/sec). Whisper thus exploits a usable sound source without demanding a large air supply from the respiratory system but it does require considerable overall laryngeal tension. Whisper could arguably be omitted as a nonlinguistic phenomenon.


( MODAL ) VOICE : The full glottis functions as a single unit, the vocal cords/folds vibrate regularly with complete closure on each vibration (see Fig. 6 on page 3). All languages have voiced sounds and all vowels are voiced. The distinction between voiceless and voiced sounds applies in a high proportion of the world’s languages though it is certainly not universal.

FALSETTO
/

/ (also head register, head voice): a distinctive phonation type in which the vocal folds are stretched longitudinally
/

/, yielding a thin cross-section, and usually leaving the glottis slightly open. The fundamental frequency produced is very much higher than in modal voice, typically around three times as high for males; subglottal pressure is lower, and there is often a slight whispery quality as the air leaks through the glottis (see Fig. 7 on page 4);

CREAK : It is a phonation mode characterised by low frequency vibration of the vocal folds (typically 20—60 Hz). The cords open only for a short time and often quite irregularly from cycle to cycle of vibration. The entire glottis is held laterally compressed but untensed, except for a small opening near the anterior
(ligamental) end. There is some uncertainty among linguists how creak is articulated. (Trask 1996:97)

COMPLETE CLOSURE : It is similar to nil phonation in the sense that nil phonation is sometimes extended to cover total closure of the glottis, with no airflow at all. (See Fig. 8 on page 4.) In some dialects, plosives can be replaced by the glottal stop [

].
● chocolate [
 ], ● that way [
 ], ● What do you want?
[

]
(Trask 1996)

COMBINATORY PHONATION MODES
: In addition to the phonation types discussed above some further combinatory phonation types must be allowed for, considered. They include BREATHY CREAK , in which creak is accompanied by some turbulent air leakage to produce breathiness, and
VOICED CREAK
, in which creak and normal voice are combined.

THE ARTICULATION OF THE SOUND
/h/: Although it is not a phonation type and it is not an auxiliary function of the larynx that can support other processes of the articulation, it is worth mentioning here because the sound is articulated in the larynx (it is a glottal fricative).
VOICED CREAK
(Of the voice) produced by vibration of a small portion of the vocal cords while the arytenoid cartilages are held together, with little breath being released
(RHD-II)
VOICED CREAK / CREAKY VOICE / LARYNGEALISATION

A compound phonation type in which one part of the glottis produces creak while another part of it produces ordinary voicing. The precise mechanism of this is not well understood, and it may well differ from speaker to speaker. IPA represents creaky voice with a tilde placed below the symbol for the corresponding segment with ordinary voicing. (Trask 1996:97)