Effects of tonsillectomy on articulation.

Changes in the articulation of 5 Japanese vowels before and after tonsillectomy were compared using the formants as indicators. Data from 40 patients were analyzed and those from 10 healthy volunteers were adopted as control. The comparison of formant frequencies before and 1 month after operation revealed that F1, F2 and F4 remained within the range of intra-individual fluctuations in most cases. F3, however, exceedingly decreased in many cases, and the decrease was particularly marked for /o/. No evident change was observed as to formant bandwidth. The larger the tonsil was, the more changes were seen in the formant frequency. The evaluation according to Mackenzie's classification was found to be unsatisfactory. Observing the postoperative changes over time, it is suggested that the altered vocal tract slowly compensates by means of the surrounding tissues. From the acoustic evaluation, the changes in the articulation due to surgery were considered to be negligible in clinical practice, although in professional vocalists it seemed to be a problem that cannot be disregarded.