The Effects of Babble Noise on the Recognition of Persian Vowels in the Fourth and Fifth Decades of Life.

Routine verbal communication almost never occurs in quiet. Speech perception disorder in noise is one of the most common complaints of people of all ages. In our living environment, there are different types of background noise that have different masking effects. In general, verbal noises have more signal target masking. Babble noise as an interfering factor can lead to speech perception disorders. Speech phonemes are alienated into consonants and vowels across languages. These phonemes are different in terms of production and perceptual mechanism. Persian has 6 vowels /i/, /e/, /a/, /â/, /o/, and /u/. Vowels are the nucleus of the syllables and words, vowel errors can lead to disorders in speech perception process. Now the question arises as to whether the ability of vowel recognition in the presence of babble noise is influenced by age, signal to noise ratio, gender, and educational level? Also, if the above factors affect the recognition of the Persian vowel, which vowels are more vulnerable to these effects?Therefore, due to the absence of similar studies on the effect of the aforementioned factors on the recognition of Persian vowels, the present study examined the effect of age, signal to noise ratio, sex, and educational level on the recognition of Persian vowel in the fourth and fifth decades of life. This observational and cross sectional study was performed on 60 adults with normal hearing in the age range of 30-49 years with mean and standard deviation (SD) of 38.88±6.23 years old (thirty people aged 30 to 39 years old with average age and standard deviation (SD) of 33.40±2.35 years and thirty aged 40 to 49 years with average age and standard deviation (SD) of 44.73±2.33 years) from available samples. After the auditory and speech evaluation, the recognition of Persian vowels were examined in consonant-vowel-consonant syllable in the presence of babble noise in signal-to-noise ratios of 0, -5 and -10, along with  the randomized presentation of stimuli to the right ear. The purpose of the random presentation of syllables in the present study was to avoid memorizing words.Comparison the recognition score of six Persian vowels showed significant differences in three signal-to-noise ratios (p = 0.001). Also, comparison the vowels recognition scores were significant in two age ranges of 30-39 and 40-49 years old in three signal-to-noise ratios (p = 0.001). However, not found significant differences between the sexes (P= 0.991) and different educational levels (P= 0.282). Also, in three signal to noise ratios of 0, -5 and -10, the recognition scores of the front vowels were better than the back vowels. In signal-to-noise ratios of 0 and -5, the highest mean of recognition score was associated with / a / vowel and in the signal-to-noise ratio of -10 with / i / was present. Also, there was the lowest mean of recognition score in signal-to-noise ratios 0, -5 and -10 with / u / vowel. The present study showed that the average recognition of Persian vowels is affected by age, signal-to-noise ratio, and type of vowel. As the age increases and the signal-to-noise ratio decreases, the average recognition score of the vowels decreases significantly in the presence of babble noise