A comparison of formant frequencies for vowels pronounced in the supine and upright positions

The purpose of the study reported was to examine whether there is an acoustical difference between vowels produced by a speaker in the supine and upright positions. Considering the facts presented, perhaps it can be concluded that generally, when subjects assume the supine position the point of maximum construction moves back, causing F₁ to increase. However, it is not yet clear whether gravity or head position played a role in this effect since head position was not controlled.