Effects of vocal loudness on vowel nasalance among normal Farsi-speaking students with the age range of 18-28 years

Nasality is an important parameter needing to be considered in studying voice resonance pathology. The voice of normal adults typically shows varying degrees of nasality. It appears that nasality, like the other parameters of voice, is affected by loudness and this can be measured through experimental evaluations. The aim of the present study was to determine the effect of vocal loudness on vowel nasalance in a group of 18-28 year-old normal Farsi- speaking subjects. In this descriptive- analytic cross- sectional study, the voice samples of 65 randomly selected normal subjects (male and female) whose ages ranged from 18 to 28 years and who spoke Farsi as their native language were studied. All subjects were the students of Rehabilitation Faculty of Iran Medical Sciences University at the time of study. The mean score of nasalance for the vowels of Farsi language was captured through Nasal View software. Descriptive statistical analyses as well as one-way ANOVA were conducted on all data of interest. In both male and female subjects, the maximum and minimum amounts of nasalance were seen at the soft and the loud voice respectively. The statistical analysis results showed that the degree of nasalance in 3 levels of soft, normal and loud voices was significantly different (P < 0.05). In normal adults, vowel nasalance decreases as vocal loudness increases. This is a feature of normal speech mechanism. This finding can be explained with regard to the functioning of velopharengeal port. So, a raise in subglottal air pressure at loud voice results in an increase in muscular contraction of pharynx and palate.