We devised a simple technique to differentiate the contribution of the oronasal fistula from that of the velopharyngeal port when abnormal nasal air flow is present. Temporary obturators were constructed from a thin sheet of dental wax and retained by a dental adhesive. Speech samples collected for aerodynamic analysis, both with and without the appliance, included both fricatives and plosives in single words and connected speech. Our results indicate that this temporary obturator, used in conjunction with aerodynamic studies, can be used to determine the etiology of abnormal nasal flows in speakers with oronasal fistulae.