Can intrinsic vowel Fo be explained by source/tract coupling?

There is extensive evidence that in the same phonetic environment the voice fundamental frequency (Fo) of vowels varies directly with vowel "height." This Fo difference between vowels could be caused by acoustic interaction between the first vowel formant and the vibrating vocal folds. Since higher vowels have lower first formants than low vowels the acoustic interaction should be greatest for high vowels whose first formant frequencies are closer in frequency to Fo. Ten speakers were used to see if acoustic interaction could cause the Fo differences. The consonant [m] was recorded in the utterances [umu] and [ama]. Although the formant structure of [m] in [umu] and [ama] should not differ significantly, the Fo of each [m] allophone was significantly different. However, the Fo of each [m] allophone did not differ significantly from the Fo of the following vowel. These results did not support acoustic interaction. However, it is quite reasonable to conclude that the Fo variation of [m] was caused by coarticulatory anticipation of the tongue and jaw for the following vowel. Another experiment is offered in order to help explain the physical causes of intrinsic vowel Fo. In this experiment Fo lowering was found at the beginning of vowels following Arabic pharyngeal approximants. This finding indicates that the Fo of pharyngeal constricting vowels, e.g., [ae] and [a], might be lowered as a result of similar articulary movements, viz. tongue compression and active pharyngeal constriction.