• Niyom Thamrongananskul D.D.S., Ph.D. (Oral Biology)
• Panarat Kodkeaw D.D.S., Higher Grad. Dip. (Maxillofacial Prosthetics)
• Sorapol Salaphan B.Sc., D.D.S.
• Hisashi Taniguchi D.D.S., Ph.D. (Dental Science)
• Piyawat Phankosol B.Sc., D.D.S., Ph.D. (Dental Science)

Objective The purpose of this study was to analyze the first formant frequency (F1) and the
second formant frequency (F2) then calculated the F1 range and the F2 range of five vowels [a],
[i], [u], [e], and [o] from Thai male volunteers who do not have oral defects.

Materials and methods Sound of five vowels [a], [i], [u], [e], and [o] from 67 volunteers from
Chiang Mai and Chulalongkorn University were recorded with digital tape recorder. The five vowel
sounds were analyzed by using Multi-speech 3700 program and Linear Predictive Coding (LPC)
method. The F1 and the F2 were found and then the F1 range and the F2 range were calculated,
respectively.

Results The F1 and the F2 from both groups of volunteers were not statistically significant
difference. When gathering the data of both groups, it was found that the highest value of the F1 and the
F2 were at [a] (706.17 Hz) and [i] (2011.16 Hz), respectively. The lowest value of the F1 and the F2
were found at [u] (282.94 Hz) and [o] (914.98 Hz), respectively. The F1 range and the F2 range were
423.23 Hz and 1096.18 Hz, respectively.

Conclusion From the F1 and the F2 of five vowels, the F1 range and the F2 range of Thai male
volunteers could be calculated. These values may be used as a standard value for sound analysis of
maxillectomy or glossectomy Thai patients when the intra-oral prostheses are performed.

(CU Dent J. 2007;30:279-86)