This study examines anticipatory pharyngealisation (i.e., emphasis) in Libyan Arabic, across a hierarchy of prosodic boundary levels (syllable vs. word vs. phonological phrase vs. intonation phrase ‘IP’) in order to quantify the magnitude, and identify the planned domain of anticipatory pharyngealisation. The acoustic manifestation of pharyngealisation is lowering in the second formant (F2) in pharyngealised contexts compared to their plain cognates. To investigate speech production models of how pharyngealisation is anticipated in advance, F2 measurements were taken at onset, mid and offset points of both vowels (V) in a word-final VCV sequence, in the context [VbV # Emphatic trigger]. The strength of [#], a prosodic boundary, was varied syntactically to manipulate the presumed hierarchical strength of that boundary from zero (where the VbV and the trigger are in the same word) up to an intonational phrase boundary. We expect that the stronger the boundary, the greater the resistance to the spread of pharyngealisation. The duration of the final vowel (i.e., the pre-trigger vowel) was also measured to assess if pharyngealisation magnitude on it and on the first vowel is influenced by the temporal proximity to the emphatic trigger. Results show (1) that within word boundaries pharyngealisation effects are present on both vowels, and (2) there are effects of pharyngealisation on the final vowel, i.e. the pre-trigger across word and phrase boundaries, and (3) there is no evidence of pharyngealisation across an IP boundary. An examination of the pre-trigger vowel + pause duration suggests that the lack of coarticulatory effects on the final vowel, i.e., pre-trigger vowel, across an IP boundary may be due to the temporal distance from the trigger: all tokens in this condition had a pre-trigger pause. For word and phrase boundary conditions, F2 was higher the greater the temporal distance from the pharyngealised trigger. These results suggest that anticipatory pharyngealisation is qualitatively different within the word as compared to across word boundaries. More clearly, the magnitude of pharyngealisation is categorical within word boundaries, and gradient across prosodic boundaries higher than the word. These findings suggest that pharyngealisation within the word is phonological, whereas across word boundaries it is primarily a phonetic process, conditioned by the temporal proximity to the pharyngealised trigger. Results also show that the planned domain of [pharyngealisation] is the word. However, additional phonetic pharyngealisation effects can extend across word boundaries as a result of coarticulation.