Comparison of nasalance scores obtained with the nasometers 6200 and 6450

Ground-truth validation of the "earbuds method" for measuring acoustic nasalance

Among the variety of methodological tools available for quantifying the degree of nasalization, nasometry has remained a popular choice for both academic and clinical research on speech due to its relatively low cost, portability, ease of use, and interpretability. In its simplest form, nasometry involves two microphones that independently capture the acoustic radiation from the mouth and nose. Recently, a method was proposed by Stewart and Kohlberger [(2017). Lang. Doc. Conserv. 11, 49-80] of using earbuds to achieve a similar result. Although the method has been widely used since, most notably in the context of linguistic fieldwork, it has yet to be tested against ground-truth measurements of acoustic nasalance from a commercially established device; the current study attempts to provide this ground-truth comparison. A wide variety of characteristics of the relationship between nasalance measurements created using acoustic data co-registered from a commercial nasometer, silicone earbuds, and flat earbuds are thoroughly examined. The results suggest that the "earbuds method" may provide reliable estimates of nasality when assessed at a global level (i.e., overall averages, relatively high/low nasalance scores coinciding with the presence/absence of nasalization), but that the accuracy of these estimates may decline at more fine-grained levels in different ways that are outlined in the discussion.

The Role of Instructions in Motor Learning of Oral Versus Nasalized Speech Targets

PURPOSE

The purpose of this study was to investigate how general, implicit instructions with auditory-perceptual emphasis; specific, explicit instructions with biomechanical focus; or both affect learning of oral-nasal balance control in speech.

METHOD

Thirty healthy, vocally untrained participants were assigned to one of three instructional groups (i.e., implicit, explicit, and integrated) and learned to produce oral versus nasalized vowel-, syllable-, and phrase-level targets during once-weekly sessions over 4 weeks. Learning gains and performance variability were analyzed using nasometry.

RESULTS

We observed a significant main effect of instruction type on learning gains at phrase level (p = .016). Specifically, the integrated group (M = 59.8%) significantly outperformed the explicit group (M = 37.9%) and numerically outperformed the implicit group (M = 45.1%). For nasalized phrase targets, results revealed a significant main effect of instruction type on performance variability (p = .042), but pairwise comparisons between instruction groups were not significant.

CONCLUSIONS

The integration of implicit processes via auditory-perceptual modeling and explicit processes via relevant biomechanical directives resulted in larger motor learning gains, especially at higher levels of task complexity (i.e., phrase) compared to providing implicit or explicit instruction alone. The higher performance variability (i.e., less stable productions) that was sometimes induced by explicit instruction did not negatively impact learning when integrated with implicit instruction. Clinical implications for speech/voice therapy models are discussed.

Automatic Detection System for Velopharyngeal Insufficiency Based on Acoustic Signals from Nasal and Oral Channels

Velopharyngeal insufficiency (VPI) is a type of pharyngeal function dysfunction that causes speech impairment and swallowing disorder. Speech therapists play a key role on the diagnosis and treatment of speech disorders. However, there is a worldwide shortage of experienced speech therapists. Artificial intelligence-based computer-aided diagnosing technology could be a solution for this. This paper proposes an automatic system for VPI detection at the subject level. It is a non-invasive and convenient approach for VPI diagnosis. Based on the principle of impaired articulation of VPI patients, nasal- and oral-channel acoustic signals are collected as raw data. The system integrates the symptom discriminant results at the phoneme level. For consonants, relative prominent frequency description and relative frequency distribution features are proposed to discriminate nasal air emission caused by VPI. For hypernasality-sensitive vowels, a cross-attention residual Siamese network (CARS-Net) is proposed to perform automatic VPI/non-VPI classification at the phoneme level. CARS-Net embeds a cross-attention module between the two branches to improve the VPI/non-VPI classification model for vowels. We validate the proposed system on a self-built dataset, and the accuracy reaches 98.52%. This provides possibilities for implementing automatic VPI diagnosis.

Normative nasalance scores in Chilean adults

PURPOSE

The present study is aimed towards determining and comparing normative nasalance scores in Chilean Spanish-speaking adult men and women.

METHODS

40 women (age range 18 to 35, X = 25.79, SD = 5.83) and 36 men (age range 18 to 35, X = 26.45, SD = 4.08) were invited to participate, all of them without any previous speech therapy, neurological pathologies, intellectual deficits, hearing loss, syndromes, or other diagnosed pathologies that could impact speech production.A study of proper velopharyngeal function was performed, using a perceptual resonance evaluation. Nasalance was determined using a model 6450 Nasometer, during the reading of three standardized speech samples in Spanish: a nasal passage (NP), an oronasal passage (ONP), and an oral passage (OP). Also, the nasalance distance was calculated. Genders were compared using Wilcoxon tests for independent samples.

RESULTS

The NP presented the highest percentage of nasalance, with 52.13% (± 4.73), followed by the ONP with 25.38% (± 3.7), and finally the OP, which presented the lowest value of 14.15% (± 5.03). Meanwhile, nasalance distance was 37.98% (± 5.32). Finally, no significant differences were observed when comparing the nasalance between genders (p >0.05).

CONCLUSION

The nasalance values obtained were similar to those observed for other Spanish speakers. Also, male and women showed similar scores. The results of this study are a contribution to the indirect assessment of velopharyngeal function in Chilean adults.

Effects of different calibration schedules on the test-retest differences of nasalance scores obtained with the Nasometer 6450

Nasometry is used to assess nasality in speech but it is unclear whether overly frequent recalibration of the instrument adds measurement errors. The goal of the present research study was to describe the effect of the Nasometer 6450 calibration on the nasalance scores of repeated recordings. In a first experiment, the Nasometer calibration values stored in the computer's registry were manipulated to investigate the impact on nasalance scores. In the second experiment, a set of pre-recorded speech samples was re-recorded 40 times with a Nasometer 6450 in 4 different calibration regimens: Short-term repeated recordings without (R1) and with recalibration (R2C), and long-term repeated recordings over 10 days without (R3) and with recalibration (R4C). The first experiment showed that, compared to a calibration value of 1.0, a value of 0.9 resulted in nasalance scores that were on average 3 points lower while a calibration value of 1.1 resulted in scores that were 0.5 points higher. The results of the second experiment showed test-retest differences of less than 2 nasalance points for 91% of the data for a non-nasal stimulus. For a nasal stimulus, 91% of data were within 5 points for R3 and R4C. The results suggested that frequent recalibration of the Nasometer may slightly increase test-retest differences of nasalance scores. An alternative procedure for verifying microphone balance without recalibration is suggested.

Covering Nasometer Microphones with Plastic Wrap for Infection Control Increases Retest Variability of Nasalance Scores

The Nasometer is a popular instrument for the acoustic assessment of nasality. In light of the currently ongoing COVID-19 global pandemic, clinicians may have wondered about the infection control procedures for the Nasometer. The current research investigated whether nasalance scores are affected if the Nasometer 6450 microphone casings are covered with a material such as rolled polyvinyl chloride household wrap. For the experiment, pre-recorded sound files from two speakers were played back through a set of small loudspeakers. Nasalance scores from two baselines and three wrap cover conditions were compared. While there was no statistically significant condition effect in a repeated-measures analysis of variance, the within-condition cumulative differences in nasalance scores were 2 for the initial baseline, 42 for wrap cover 1, 24 for wrap cover 2, 78 for wrap cover 3, and 8 for the final baseline. Mean differences between the wrap cover and the baseline conditions were 8.2 to 15.3 times larger, and cumulative differences were 8.3 to 16.6 times larger than between the two baselines. Based on the higher cumulative and mean differences observed, clinicians should not cover Nasometer microphones with household wrap as this increases variability of nasalance scores. Since there is evidence that the COVID-19 virus can survive for some time on metal surfaces, clinicians should be mindful of the fact that the Nasometer microphone housings can only be cleaned superficially and should be handled with gloves to minimize any possible risk of touch transfer of pathogens to the next speaker or the clinician.

Normative nasalance scores in Tamil-speaking Indian children

OBJECTIVE

The aim of this study was to obtain normative nasalance scores for Indian Tamil-speaking children.

METHODS

Mean nasalance scores were obtained from 175 consecutive Tamil-speaking normal children (95 males, 80 females) aged 5-16 years during the repetition of six standardized sentences: two oral, two oronasal, and two nasal sentences. The nasal view was used to obtain nasalance scores for the standardized sentences.

RESULTS

Group mean and standard deviation (SD) nasalance scores of children for oral, oronasal, and nasal sentence were 35.65(SD 7.20), 44.42(SD 7.37), and 57.21(SD 8.15), respectively. The mean nasalance values of children aged 9-12 years were greater than children aged 5-8 years and 13-16 years for nasal sentences (p < .001). Males were found to have significantly higher nasalance scores for oral and oronasal sentences (p < .05) although these differences were within the range of normal variation.

CONCLUSIONS

The present study provides normative nasalance scores for Tamil-speaking Indian children.

Measurement of Nasalance Scores Without Touching the Philtrum for Better Comfort During Speech Assessment and Therapy: A Preliminary Study

OBJECTIVE

The Kay Pentax nasometer uses a separator plate that touches the philtrum of a patient to separate the nasal and oral sound energies for nasalance measurement. However, the separator plate can restrict the natural movement of the patient's upper lip and generate unpleasant pressure on the patient's philtrum. The present study was intended to measure nasalance scores without touching the philtrum for better comfort during speech assessment and therapy.

METHODS

Nasalance scores of 10 males and 10 females having no speech disorders were measured under 4 levels (0, 5, 10, and 15 mm) of the gap between the plate and the philtrum (denoted as plate-to-philtrum gap) using Nasometer II 6450 for nasal (Nasal Sentences) and oral (Zoo Passage) stimuli. Regression formulas were established to examine the relationships between nasalance score and plate-to-philtrum gap for the stimuli. To provide nasalance scores equivalent to those measured for the contact condition, compensation factors for the 5 mm plate-to-philtrum gap measurement condition were identified for the stimuli.

RESULTS

The nasalance scores were significantly different between the 4 different plate-to-philtrum gaps for the stimuli. Compensation factors for the Nasal Sentences and the Zoo Passage were identified as 1.17 and 0.71, respectively.

CONCLUSIONS

The 5 mm plate-to-philtrum gap condition after multiplying the compensation factors can provide equivalent nasalance scores to the conventional contact measurement condition which may provide better comfort in speech assessment and therapy.

Immediate effects of voice focus adjustments on hypernasal speakers' nasalance scores

OBJECTIVES

To explore the immediate effects of voice focus adjustments on the oral-nasal balance of hypernasal speakers, measured with nasalance scores.

METHODS

Five hypernasal speakers (2 M, 3 F) aged 5-12 (SD 2.7) learned to speak with extreme forward and backward voice focus. Speakers repeated oral, nasal, and phonetically balanced stimuli. Nasalance scores were collected with the Nasometer 6450.

RESULTS

From the average baseline of 34.27% for the oral stimulus, nasalance increased to 46.07% in forward and decreased to 30.2% in backward focus. From the average baseline of 64.53% for the nasal stimulus, nasalance decreased to 64.13% in forward and decreased to 51.73% in backward focus. From the average baseline of 51.33% for the phonetically balanced stimulus, nasalance increased to 58.87% in forward and decreased to 46.2% in backward focus.

CONCLUSIONS

Forward voice focus resulted in higher and backward voice focus resulted in lower nasalance scores during speech for a group of hypernasal speakers. However, there was an exception: One male speaker showed decreased nasalance in forward voice focus. Future research should investigate the longer-term effectiveness of the intervention.

Influence of Altered Auditory Feedback on Oral-Nasal Balance in Speakers of Brazilian Portuguese

Purpose This study explored the role of auditory feedback in the regulation of oral-nasal balance in speakers of Brazilian Portuguese. Method Twenty typical speakers of Brazilian Portuguese (10 male, 10 female) wore a Nasometer headset and headphones while continuously repeating stimuli with oral and nasal sounds. Oral-nasal balance was quantified with nasalance scores. The signals from 2 additional oral and nasal microphones were played back to the participants through the headphones. The relative loudness of the nasal channel in the mix was gradually changed, so that the speakers heard themselves as more or less nasal. Results A repeated-measures analysis of variance of the mean nasalance scores of the stimuli at baseline, minimum, and maximum nasal feedback conditions demonstrated significant effects of nasal feedback condition (p < .0001) and stimuli (p < .0001). Post hoc analyses demonstrated that the mean nasalance scores were lowest for the maximum nasal feedback condition. The scores of the minimum nasal feedback condition were significantly higher than 2 of 3 baseline feedback conditions. The speaking amplitude of the participants did not change between the nasal feedback conditions. Conclusions Increased nasal signal level feedback led to a compensatory adjustment in the opposite direction, confirming that oral-nasal balance is regulated by auditory feedback. However, reduced nasal signal level feedback resulted in a compensatory response that was lower in magnitude. This suggests that, even in Brazilian Portuguese, a language with phonetic and phonological vowel nasalization, decreased nasality was not perceived as critically as increased nasality by the speakers.

Normative nasalance scores in the production of words and syllables for Brazilian Portuguese speakers

The objective of this study was to determine normative nasalance scores for non-cleft children, adolescents and adults, native speakers of Brazilian Portuguese, during the production of words and syllables, for cross-linguistic comparisons in populations with and without cleft palate. Nasalance was assessed in 62 individuals, aged 6-10 years (n = 20), 11-17 years (n = 20) and 18-35 years (n = 22), using a nasometer II model 6450 (KayPENTAX), during production of one sequence of nine oral words (pipa, bis, burro, tatu, pilha, cuca, gui, fila, luz) and of sequences of isolated syllables (e.g. pa, pa, pa, pa, pa, pa) composed of plosive, fricative, liquid and nasal consonants with high and low vowels. In order to validate the new nasalance stimuli, nasalance scores for traditional oral and nasal stimuli were also obtained. Differences were analyzed at a significance level of 0.01. Mean nasalance scores (±SD) during the production of the sequence of words were 18 ± 5% (children), 18 ± 7% (adolescents) and 21 ± 5% (adults). Differences between age groups were not significant. During the production of syllables, adults had the highest mean nasalance scores (except for syllable /mi/); significant differences between age groups were observed only for /pa/ ,/sa/ and /la/. Nasalance scores were significantly higher in oral and nasal syllables with high vowels than with low vowels, and in nasal syllables than in oral syllables with high and low vowels. The nasalance scores obtained for the sentences were comparable to previously established norms. In conclusion, the nasalance scores defined for Brazilian Portuguese speakers, in different stimuli, may be adopted as normative values for local and cross-language comparisons in the identification of hypernasality related to conditions such as cleft palate, neurogenic disorders and syndromes.

Effect of vowel context on test-retest nasalance score variability in children with and without cleft palate

OBJECTIVE

The purpose of this study was to determine whether test-retest nasalance score variability differs between Korean children with and without cleft palate (CP) and vowel context influences variability in nasalance score.

PARTICIPANTS

Thirty-four 3-to-5-year-old children with and without CP participated in the study.

METHODS

Three 8-syllable speech stimuli devoid of nasal consonants were used for data collection. Each stimulus was loaded with high, low, or mixed vowels, respectively. All participants were asked to repeat the speech stimuli twice after the examiner, and an immediate test-retest nasalance score was assessed with no headgear change.

RESULTS

Children with CP exhibited significantly greater absolute difference in nasalance scores than children without CP. Variability in nasalance scores was significantly different for the vowel context, and the high vowel sentence showed a significantly larger difference in nasalance scores than the low vowel sentence. The cumulative frequencies indicated that, for children with CP in the high vowel sentence, only 8 of 17 (47%) repeated nasalance scores were within 5 points.

CONCLUSIONS

Test-retest nasalance score variability was greater for children with CP than children without CP, and there was greater variability for the high vowel sentence(s) for both groups.

Application of linear discriminant analysis to the nasometric assessment of resonance disorders: a pilot study

Objective : Nasalance scores have traditionally been used to assess hypernasality. However, resonance disorders are often complex, and hypernasality and nasal obstruction may co-occur in patients with cleft palate. In this study, normal speakers simulated different resonance disorders, and linear discriminant analysis was used to create a tentative diagnostic formula based on nasalance scores for nonnasal and nasal speech stimuli. Materials and Methods : Eleven female participants were recorded with the Nasometer 6450 while reading nonnasal and nasal speech stimuli. Nasalance measurements were taken of their normal resonance and their simulations of hyponasal, hypernasal, and mixed resonance. Results : A repeated-measures analysis of variance revealed a resonance condition-stimuli interaction effect (P < .001). A linear discriminant analysis of the participants' nasalance scores led to formulas correctly classifying 64.4% of the resonance conditions. When the hyponasal and mixed resonance conditions with obstruction of the less patent nostril were removed from the analysis, the resultant formulas correctly classified 88.6% of the resonance conditions. Conclusion : The simulations produced distinctive nasalance scores, enabling the creation of formulas that predicted resonance condition above chance level. The preliminary results demonstrate the potential of this approach for the diagnosis of resonance disorders.

Influence of Altered Auditory Feedback on Oral-Nasal Balance in Speech

PURPOSE

This study explored the role of auditory feedback in the regulation of oral-nasal balance in speech.

METHOD

Twenty typical female speakers wore a Nasometer 6450 (KayPentax) headset and headphones while continuously repeating a sentence with oral and nasal sounds. Oral-nasal balance was quantified with nasalance scores. The signals from 2 additional oral and nasal microphones were played back to the participants through the headphones. The relative loudness of the nasal channel in the mix was gradually changed so that the speakers heard themselves as more or less nasal. An additional amplitude control group of 9 female speakers completed the same task while hearing themselves louder or softer in the headphones.

RESULTS

A repeated-measures analysis of variance of the mean nasalance scores of the stimulus sentence at baseline, minimum, and maximum nasal feedback conditions demonstrated a significant effect of the nasal feedback condition. Post hoc analyses found that the mean nasalance scores were lowest for the maximum nasal feedback condition. The scores of the minimum nasal feedback condition were significantly higher than 2 of the 3 baseline feedback conditions. The amplitude control group did not show any effects of volume changes on nasalance scores.

CONCLUSIONS

Increased nasal feedback led to a compensatory adjustment in the opposite direction, confirming that oral-nasal balance is regulated by auditory feedback. However, a lack of nasal feedback did not lead to a consistent compensatory response of similar magnitude.

Short-term and long-term test-retest reliability of the Nasality Severity Index 2.0

PURPOSE

The Nasality Severity Index 2.0 (NSI 2.0) forms a new, multiparametric approach in the assessment of hypernasality. To enable clinical implementation of this index, the short- and long-term test-retest reliability of this index was explored.

METHODS

In 40 normal-speaking adults (mean age 32y, SD 11, 18-56y) and 29 normal-speaking children (mean age 8y, SD 2, 4-12y), the acoustic parameters included in the NSI 2.0 (i.e. nasalance of the vowel /u/ and an oral text, and the voice low tone to high tone ratio (VLHR) of the vowel /i/) were obtained twice at the same test moment and during a second assessment two weeks later. After determination of the NSI 2.0, a comprehensive set of statistical measures was applied to determine its reliability.

RESULTS

Long-term variability of the NSI 2.0 and its parameters was slightly higher compared to the short-term variability, both in adults and in children. Overall, a difference of 2.82 for adults and 2.68 for children between the results of two consecutive measurements can be interpreted as a genuine change. With an ICC of 0.84 in adults and 0.77 in children, the NSI 2.0 additionally shows an excellent relative consistency. No statistically significant difference was withheld in the reliability of test-retest measurements between adults and children.

CONCLUSION

Reliable test-retest measurements of the NSI 2.0 can be performed. Consequently, the NSI 2.0 can be applied in clinical practice, in which successive NSI 2.0 scores can be reliably compared and interpreted.

LEARNING OUTCOMES

The reader will be able to describe and discuss both the short-term and long-term test-retest reliability of the Nasality Severity Index 2.0, a new multiparametric approach to hypernasality, and its parameters. Based on this information, the NSI 2.0 can be applied in clinical practice, in which successive NSI 2.0 scores, e.g. before and after surgery or speech therapy, can be compared and interpreted.

Application of Linear Discriminant Analysis to the Long-term Averaged Spectra of Simulated Disorders of Oral-Nasal Balance

OBJECTIVE

Acoustic studies of oral-nasal balance disorders to date have focused on hypernasality. However, in patients with cleft palate, nasal obstruction may also be present, so that hypernasality and hyponasality co-occur. In this study, normal speakers simulated different disorders of oral-nasal balance. Linear discriminant analysis was used to create a tentative diagnostic formula based on the long-term averaged spectra (LTAS) of the speech stimuli.

MATERIALS AND METHODS

Eleven female participants were recorded while reading nonnasal and nasal speech stimuli. LTASs of the recordings were run for their normal oral-nasal balance and their simulations of hyponasal, hypernasal, and mixed oral-nasal balance. The amplitude values (in decibels) were extracted in 100-Hz intervals over a range of 4 kHz.

RESULTS

A repeated-measures analysis of variance of the normalized amplitudes revealed a resonance condition-frequency band amplitude interaction effect (P < .001). A linear discriminant analysis of the participants' LTAS led to formulas correctly classifying 80.7% of the oral-nasal balance conditions.

CONCLUSION

The simulations produced distinctive spectra enabling the creation of formulas that predicted the oral-nasal balance above chance level. Future research with speakers with oral-nasal balance disorders will be needed to investigate the potential of this approach for the clinical diagnosis of disorders of oral-nasal balance.