Investigation and Comparison of the Normative Nasalance Score in Normal Persian-Speaking Men and Women Aged 21-33 Years

¹ Student Research Committee, Hamadan University of Medical Sciences, Hamadan, Iran

² Department of Speech Therapy, School of Rehabilitation, Hamadan University of Medical Sciences, Hamadan, Iran

³ Department of Biostatistics, School of Health, Hamadan University of Medical Sciences, Hamadan, Iran

*Corresponding author: Kowsar Baghban, Department of Speech Therapy, School of Rehabilitation, Hamadan University of Medical Sciences, Hamadan, Iran. Email: baghban.kowsar@gmail.com

EXTENDED ABSTRACT

Background

Resonance is a fundamental acoustic property of speech that reflects shaping of sound in the supralaryngeal vocal tract, including the pharyngeal, oral, and nasal cavities [1–3]. During normal speech, the velopharyngeal valve rapidly closes for oral sounds and opens for nasal sounds, thereby regulating the transmission of acoustic energy and airflow between the oral and nasal cavities [4, 5]. Abnormal distribution of acoustic energy through these cavities can produce resonance disorders such as hypernasality, hyponasality, cul-de-sac resonance, or mixed patterns [6, 7]. Although perceptual judgment is central to clinical assessment, it may be influenced by rating scales and other speech characteristics; therefore, instrumental measures can provide an objective complement [8–11]. Nasometry is a non-invasive acoustic method that quantifies the relative nasal component of speech and can provide reference values for diagnosis and treatment planning. Normative nasalance scores are language-, dialect-, age-, speech-context-, and sometimes sex-dependent [12–19]. Persian normative data have previously been reported mainly for children and adolescents, leaving limited information for young adults. The present study therefore aimed to determine normative nasalance scores in healthy Persian-speaking adults aged 21-33 years and to examine whether sex was associated with nasalance across syllables, sustained sounds, carrier phrases, and connected speech.

Methods

This descriptive-analytical, non-experimental study was conducted in Hamadan, Iran, in 2024. A convenience sample of 106 healthy Persian-speaking adults aged 21-33 years was included, with equal numbers of men and women (53 in each group). The target sample size of 53 participants per sex was determined from a previous Persian nasometry study [4]. Participants were recruited from educational centers, Hamadan University of Medical Sciences, Bu-Ali Sina University, and libraries in different areas of Hamadan. Eligibility required Persian as the dominant first language, absence of a detectable accent in everyday communication, and no structural oral or nasal abnormality, velopharyngeal dysfunction, hearing disorder, speech sound production disorder, resonance disorder, or voice disorder. Individuals with acute nasal obstruction or congestion on the assessment day, including common cold, rhinitis, sinusitis, nasal polyps, medication-related congestion, enlarged tonsils, severe septal deviation, a dominant non-Persian language, or inability to read and repeat the required stimuli were excluded. Three individuals were excluded because of a cold and one because of non-cooperation, leaving 106 participants for analysis. Testing was performed in the acoustic laboratory of the School of Rehabilitation using an ANDREA nasometer (SN: 8538) with Ic Speech software. The speech protocol comprised the SNAP test, whose Persian version had previously undergone validity and reliability assessment [20], the Bahareh's Bag text [21], and the Rainbow Passage [22]. SNAP included high-pressure consonant-vowel syllables, low-pressure consonant-vowel syllables, nasal syllables, sustained vowels /a/ and /i/, sustained consonants /m/ and /s/, and five carrier-phrase groups focused on bilabial plosives, alveolar plosives, velar plosives, sibilant fricatives, and nasal consonants. Participants listened to standard recorded models and repeated each required item while the nasometer separator plate was positioned between the nose and upper lip. Calibration was performed before sampling, and productions affected by coughing, sneezing, unintended phonation, repetition, or production error were discarded and repeated. Mean nasalance scores were calculated separately for each stimulus. Statistical analysis was performed in IBM SPSS version 16. Means and standard deviations were calculated for each speech context, and independent-samples t tests compared men and women. Statistical significance was set at P<0.05. The study was approved by the Ethics Committee of Hamadan University of Medical Sciences (IR.UMSHA.REC.1403.592), and written informed consent was obtained.

Results

All 106 participants completed the final analysis. The mean age was 26.09±3.76 years in men and 24.79±3.53 years in women; both groups ranged from 21 to 33 years. Across most speech contexts, normative nasalance values were similar between sexes. Two comparisons reached statistical significance. For the syllable /ʃa/, men had a mean nasalance score of 14.30±4.41 compared with 12.21±4.18 in women (P=0.01). For the carrier phrase focused on alveolar plosive consonants, the corresponding values were 16.47±4.60 in men and 14.71±3.75 in women (P=0.03). In both significant contexts, the mean nasalance score was higher in men.

Table 2. Mean (%) and standard deviation of nasalance scores in normal Persian-speaking men and women aged 21-33 years.

No significant sex difference was found for the other high-pressure syllables /pa/, /ta/, /ka/, /sa/, /pi/, /ti/, /ki/, /si/, and /ʃi/; for the nasal syllables /ma/, /na/, /mi/, and /ni/; for the low-pressure syllables /ra/, /la/, /ja/, /ri/, /li/, and /ji/; or for sustained /a/, /i/, /s/, and /m/. Similarly, sex was not significantly associated with nasalance in the bilabial plosive, velar plosive, sibilant fricative, or nasal carrier phrases. The connected-speech measures were also comparable: the Rainbow Passage yielded 33.43±4.96 in men and 33.81±6.33 in women (P=0.73), while Bahareh's Bag yielded 17.66±4.41 and 18.33±6.45, respectively (P=0.53). The nasal carrier phrase produced 46.66±6.28 in men and 46.36±7.47 in women (P=0.82), and sustained /m/ produced high nasalance values in both groups (87.44±6.05 versus 85.73±7.87; P=0.21), consistent with the expected nasal character of these stimuli. Overall, the detailed normative profile demonstrates that sex-related differences were limited to two specific speech contexts rather than being a general feature of Persian nasalance in this age range. The complete normative values for all tested contexts are presented in Table 2.

Conclusion

Normative nasalance scores for Persian-speaking adults aged 21-33 years were established across a broad set of syllables, sustained sounds, carrier phrases, and connected-speech materials. Men showed significantly higher scores only for /ʃa/ and the alveolar plosive carrier phrase, whereas most other contexts showed no significant difference between men and women. These results provide age-specific reference data that can be used as a baseline when complementing perceptual assessment with nasometric measurement in Persian-speaking adults, particularly when evaluating suspected resonance disorders and borderline velopharyngeal dysfunction. The findings also support the need to interpret nasalance values in relation to the specific speech stimulus rather than assuming a uniform sex effect across contexts.

Keywords: Nasality, Persian language, Resonance

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