As part of an analysis by synthesis approach to studying vocal intensity control in falsetto register, volumetric imaging of the vocal tract (the upper airway from the glottis to the lips) using electron beam computed tomography was performed on a classically trained singer, a countertenor, who uses a falsetto singing technique. Eight pitch and loudness conditions were imaged, a subset of which will be presented here. Each set of scans consisted of contiguous 3 mm axial `slices' encompassing the arch of the hard palate superiorly and the first tracheal ring inferiorly. Images were analyzed in three stages: image segmentation, 3D airway reconstruction and airway measurement. The vocal tract airway was segmented from surrounding tissue by assigning airway voxels a unique gray scale value. Reconstruction of the vocal tract in three dimensions was accomplished using shape based interpolation on the segmented images. Cross-sectional areas and vocal tract length were acquired from shape based interpolated data. Vocal tract area functions derived from these measurements were used to simulate the subject's phonations, which in turn allowed estimation of glottal and supraglottal contributions to vocal intensity.