In the field of speech research it is agreed that more real data is required to improve the articulatory modelling of the vocal tract. Acoustic techniques may be used to acquire vocal tract data. The advance of digital signal processing has allowed the development of new experimental techniques that allow fast and efficient measurements. DSP based measurement systems were set up, and acoustic impedance and transfer function measurements were performed on a wide variety of subjects in DCU’s semianechoic chamber. The measurement systems are compact and reproducible. The variation of the wall vibration load was investigated in a wide range of human subjects. The investigation was prompted by the question: Is the wall vibration load important in the study and implementation of vocal tract and articulatory models? The results point to the possible need in acoustic to articulatory inversion, of adapting the reference model to specific subjects by separately estimating the wall impedance load.