It is known that subglottal pressure (Psb) is a major factor in the control of fundamental frequency (F0) in speech. Yet, the details of this relation remain unclear. Estimates of the F0 to Psb ratio (FPR) from speech and special phonation tasks yield values between 5 and 15 Hz/cmH2O [1,2,3,4]. In another type of experiments pressure variations are induced externally, either subglottally or supraglottally. The FPR's measured in these experiments tend towards values of 2-5 Hz/cmH2O [5,6,7,8]. There seems to be no a priori reason for the FPR to be different in both kinds of experiments. After all, the voice source is the same and why should it behave differently during both kinds of phonation tasks? Therefore we carried out experiments that aimed at resolving this discrepancy.