Nasalance scores in noncleft individuals: why not zero?

OBJECTIVE: To determine whether oral or nasal acoustic energy is primarily responsible for nonzero nasalance scores observed during the production of nonnasal sentences by individuals with normal speech. METHOD: Sixty adults with normal speech were asked to read the Zoo passage and produce three sustained vowels, (/i/, /a/ and /u/), with and without nares occlusion. RESULTS: There was a significant decrease in nasalance scores between the unoccluded and occluded conditions for all four stimulus pairs. The mean decrease across conditions ranged from 8 (/u/) to 25 (/i/). In the unoccluded condition, the nasalance score was significantly greater for /i/ than for the other stimuli. CONCLUSIONS: The findings suggest that the majority of acoustic energy detected by the nasometer's nasal microphone during the production of nonnasal utterances is the result of sound transmission through the nose. The data obtained during this investigation, coupled with information available from other studies, suggest that this may be due to transpalatal transmission. If correct, such a conclusion would have clinical implications for patients with palatal clefts, since residual structural abnormalities and scar tissue in a repaired cleft palate may increase, dampen, or in some way alter transpalatal acoustic transmission. Thus, surgical normalization of velopharyngeal port control may not be sufficient to eliminate hypernasality in all patients.

Velopharyngeal impairment in the orthodontic population.

This article provides information concerning cleft palate teams and questions one might consider in identifying the best referral for patients manifesting velopharyngeal impairment. A discussion of the impact of velopharyngeal impairment on speech performance is followed by presentation of a variety of simple evaluative tasks that can assist the clinician in identifying patients who would benefit from referral to a cleft palate team. Finally, information is presented concerning the potential speech sequelae of maxillary advancement surgery.

Nasalance and nasal area values: cross-racial study.

Nasometry and nasal cross-sectional area data were obtained from 80 normal male and female speakers (40 African-Americans and 40 white Americans) all of whom were over the age of 18 and spoke the Mid-Atlantic dialect of American English. The nasalance scores for readings of the Zoo Passage did not differ significantly between the groups. However, nasalance scores for readings of the Nasal Sentences were found to be significantly higher among the white speakers. The pressure-flow method was used to obtain nasal cross-sectional area values. There were no racial differences in nasal cross-sectional area. The Nasal Sentences scores were not highly correlated with nasal cross-sectional area. The clinical significance of these findings is discussed.

Nasal cavity area in term infants determined by acoustic rhinometry.

The present study was undertaken to determine whether a modification to commercially available acoustic rhinometry (AR) instrumentation might allow equipment designed for use in adults to determine accurately the nasal cavity configuration of infants and children. The standard wave tube was replaced with a version having a narrow (0.312-cm2) internal diameter (ID). Before use with neonates, the accuracy of this instrument was evaluated using the nasal cavity of a full-term infant cadaver. Acoustic nasal area curves were compared to area measurements of polyvinylsiloxane nasal casts and direct volume measurements of the specimen. AR correlated well with nasal cast data (r = .88) for total nasal cavity area. The acoustic method underestimated the total area at the nasal valve by only 1.8 mm2 (22.1 mm2 vs. 23.9 mm2) and overestimated choanal area by 10 mm2 (56.9 mm2 vs. 46.9 mm2). In addition, AR measured total nasal volume to within 5.2% of the value obtained by direct measurement. In a cohort of 10 normal, term infants, the mean acoustic value for total nasal valve area was 19.2 +/- 0.05 mm2 and for total nasal volume was 1.76 +/- 0.53 cm3. This, the first report of nasal area and volume information in live infants, suggests that the modified AR device has utility both in airway research and as a nasal patency screening tool in the pediatric population.

Artifacts associated with acoustic rhinometric assessment of infants and young children: a model study.

The present study was undertaken to determine in model studies whether currently available acoustic rhinometry instrumentation might be used to analyze the nasal cavity configuration of infants and children. A simple nasal cavity model was constructed using eight Lucite inserts that were placed between standard nosepieces provided by the manufacturer and a 35-cm-long polyvinyl chloride pipe closed at its distal end. To simulate the nasal valve, the inserts were 12 mm in length and had apertures ranging in diameter from 2 to 9 mm. A series of experiments was conducted to evaluate the accuracy with which the acoustic rhinometer measured the size of each insert aperture and the configuration of the model system distal to that aperture. Transmission losses caused errors in the area measurement of the insert aperture and the tube distal to the insert. When the insert aperture was < 6 mm in diameter (0.28 cm2), the aperture area was overestimated by > 10%, whereas the area of the distal tube was underestimated by > 10%. As a result of response lags, the acoustic rhinometer also failed to provide an accurate indication of insert length. Finally, oscillation artifacts caused estimates of the distal pipe area to fluctuate. These three systematic errors are described, and their potential impact on acoustic rhinometry in children is discussed.

Hypernasality and velopharyngeal impairment.

Although the primary cause of hypernasality is impaired velopharyngeal (VP) function, a variety of other factors influence the outcome perceived by the listener. The purpose of the current study was to assess the relationship between oral-nasal resonance balance and (1) velopharyngeal orifice area; (2) nasal airflow rate; and (3) duration of nasal airflow. The pressure-flow technique was used to estimate VP area and measure nasal airflow rate and duration. Ratings of oral-nasal balance were made on a 6-point equal-appearing interval scale. Results indicated a moderate correlation between hypernasality rating and VP area (0.66), nasal airflow (0.61), and nasal airflow duration (0.53). Adults tended to be perceived as more hypernasal than children for a given degree of VP impairment. Finally, when the degree of VP opening was small, perceived oral-nasal resonance balance appeared to be related to duration of the opening-closing movements.

Perceptual assessment of resonance distortion in unoperated clefts of the secondary palate.

The purpose of this study was to examine the frequency with which five speech-language pathologists made judgments of hypernasality during the clinical assessment of young children with unoperated and repaired clefts of the secondary palate. Among the 293 nonsyndromic patients with secondary palate clefts included in this study, 219 were between 1 and 2 years of age. Of those, 83 had undergone primary palatoplasty whereas 136 had not. The remaining 74 children were between the ages of 4 and 5 years and presented with repaired secondary palatal clefts. The results showed that the clinicians were unable or unwilling to assess hypernasality in 31% of the 1 to 2 year old children with unoperated clefts. The same clinicians failed to evaluate oral-nasal resonance balance in only 12% of the children in the 1- to 2-year age group who had undergone palate repair. Only 1 of the 74 older children (1.4%) was not evaluated for hypernasality. Possible explanations for these findings are presented and discussed.

Nasometric sensitivity and specificity: a cross-dialect and cross-culture study.

A series of 514 patients seen at three clinics in the United States and Spain were evaluated using clinical judgments of hypernasality, and nasometric assessment of oral-nasal resonance balance. Data from the nasometer were obtained while patients read a passage devoid of nasal consonants. Across all subjects, the Pearson correlation coefficient between the clinical and instrumental measures was 0.78. Prediction analyses revealed that maximum efficiency was obtained using a somewhat different threshold nasalance value for each of the three patient samples. When all 514 subjects were investigated as a single group, a threshold nasalance score of 28 was found to optimize identification of patients with and without clinically significant hypernasality. In that analysis, a sensitivity of 0.87, a specificity of 0.86 and an overall efficiency of 0.87 was obtained. The clinical relevance of these findings is discussed.

Hypernasality in the presence of "adequate" velopharyngeal closure.

In some instances, hypernasality occurs despite an instrumental assessment of "adequate" velopharyngeal closure. The pressure-flow technique was used to assess the timing characteristics associated with velopharyngeal closure in 11 such subjects. The group's performance was compared to the aerodynamic characteristics of two other subject groups. One was comprised of 13 cleft palate subjects with adequate closure and normal nasal resonance, while the second group consisted of 16 noncleft subjects who also manifested normal speech. The data indicate that there are several unique timing features that differentiate the hypernasal but "adequate" group from the two control groups. These include a delay of about 50 ms in achieving closure, a longer interval of nasal emission, and a shorter duration of actual closure. Hypernasality seems to be associated with the actual time the velopharyngeal mechanism is open, rather than the volume of air escaping from the nasal chamber.

Acoustic assessment of the nasal airway.

Instrumental assessment techniques are needed to acquire quantitative information concerning the form and function of the nasal cavity. Until recently, aerodynamic methods were virtually the only source of such information. Two additional instruments are now available that purport to provide information useful to clinicians interested in assessing nasal form and function. This paper describes both the Nasometer and the acoustic rhinometer. In addition, a more traditional measure involving acoustic analysis of nasal consonants is discussed. Both the known and potential benefits and limitations of each technique are discussed.

A preliminary study of nasal airway patency and its potential effect on speech performance.

The relationship between nasal airway size and articulatory performance was studied in a group of cleft palate patients. Articulation analysis revealed that children with bilateral cleft lip and palate were nearly twice as likely to manifest compensatory articulations as children with unilateral cleft lip and palate or with cleft palate only. When subjects were grouped according to speech performance, aerodynamic assessment indicated that children with compensatory articulations had significantly larger nasal cross-sectional areas than children without compensatory articulations. The findings suggest that children with comparatively large nasal airways may be at increased risk for developing abnormal speech patterns. If these findings are confirmed by further research, such children may be candidates for relatively early palate repair.

Controlling changes in vocal tract resistance.

There is some evidence that speech aerodynamics follows the rules of a regulating system. The purpose of the present study was to assess how the speech system manages perturbations that produce "errors" within the system. Three experimental approaches were used to evaluate the physiological responses to an imposed change in airway resistance. The first involved subjects with varying degrees of velopharyngeal inadequacy. The second and third approaches involved noncleft subjects whose airway was perturbed by bleed valves and bite blocks during consonant productions. The pressure-flow technique was used to measure aerodynamic variables associated with the production of test consonants. The results of this study provide additional evidence that the speech system actively responds to perturbations in ways that tend to minimize a change in consonant speech pressures. The degree of success in stabilizing pressures appears to reflect the capability of the system to use whatever articulatory and respiratory responses are available.

The effect of gender upon nasalance scores among normal adult speakers.

Nasometry, pressure-flow, and fundamental frequency data were obtained from 15 normal female speakers and 15 normal male speakers all of whom were over the age of 18 and had Mid-Atlantic dialects. The nasalance scores and nasal cross-sectional areas of these two groups did not differ. The nasalance scores based on three standardized reading passages were not highly correlated with nasal cross-sectional area or voice fundamental frequency. The clinical significance of these findings is discussed.

Relative values of various standardized passages in the nasometric assessment of patients with velopharyngeal impairment.

A series of 155 patients referred for evaluation at the UNC Craniofacial Center was studied to compare nasometric performance data obtained from the Rainbow Passage to information provided when subjects read two other standardized passages (Zoo Passage and Nasal Sentences). Nasometric findings obtained using the three reading passages were compared to aerodynamic estimates of velopharyngeal area and nasal cross-sectional area as well as clinical judgments of hypernasality and hyponasality. The results suggest that the Rainbow Passage does not provide clinically relevant information that cannot be obtained using the other speech samples studied.

A study of nasometric values for normal nasal resonance.

It was the purpose of this study to obtain nasalance values for a large number of normal adult subjects speaking a variety of dialects of English. The Nasometer was used to measure the amount of nasal acoustic energy in the speech of 148 normal adults from four geographical regions of North America. Means and standard deviations for the nasalance and deviation scores are presented for each of three different reading passages. The Mid-Atlantic speakers were found to have significantly higher nasalance scores on all three reading passages. In addition, the female subjects had significantly higher nasalance scores on the Nasal Sentences. These differences are discussed with regard to potential reasons for their existence and implications for understanding velopharyngeal function in normal and abnormal speakers.

Increased nasal resistance induced by the pressure-flow technique and its effect on pressure and airflow during speech.

Although the validity of the pressure-flow technique has been verified in a number of laboratories, some questions still remain. The purpose of this study was to determine whether the procedures involved in estimating orifice size affect the pressure and airflow variables being measured. Twenty subjects with demonstrated velopharyngeal inadequacy on pressure-flow testing (VPO greater than or equal to 0.10 cm2) were assessed under two contrasting conditions. Subjects were asked to produce (p) in the word "hamper" with a) one nostril occluded by a cork as in pressure-flow testing and b) both nostrils patent. The results indicate that the increased nasal resistance resulting from occlusion of one nostril does not appreciably affect pressure and airflow associated with plosive consonant production in patients with velopharyngeal inadequacy.

The identification of nasal obstruction through clinical judgments of hyponasality and nasometric assessment of speech acoustics.

This study examined the records of a consecutive series of 79 patients referred for evaluation at the Oral-Facial and Communicative Disorders Program during a 3-month period in 1989. The purpose was to determine whether clinical judgments of hyponasality, based on a six-point equal-appearing interval scale or an acoustic assessment with a Kay Elemetrics nasometer could provide information concerning nasal airway patency comparable to that obtained by means of aerodynamic measurement techniques. Among the 40 adults in the series, the sensitivity of hyponasality ratings was 0.55 when nasal airway impairment was defined as a condition in which the airway was less than 0.40 and 0.71 when the definition was limited to airways of less than 0.30 cm2. Specificities for the two groups were 0.89 and 0.85, respectively. Similarly, the sensitivity of nasometer ratings was 0.30 for the first group and 0.38 for the second group, while the specificity for the two groups was 0.83 and 0.92, respectively. Comparable analyses for children were not possible because of the extent to which nasal airway size varies in children younger than 15 years of age. Possible reasons for the findings and their clinical significance are discussed.

Use of nasometry as a diagnostic tool for identifying patients with velopharyngeal impairment.

A series of 117 patients were studied in an attempt to determine the extent to which acoustic assessments of speech made with a Kay Elemetrics Nasometer corresponded with aerodynamic estimates of velopharyngeal area and clinical judgments of hypernasality. Nasometer data were obtained while patients read or repeated a standardized passage with no nasal consonants. Pressure-flow data were obtained from 96 of these patients during repeated productions of the word "papa." Listener judgments were made in a clinical setting by the senior author using a 6-point equal-appearing interval scale. Nasometer and pressure-flow results were not known to the senior author when making listener assessments. With a cutoff nasalance score of 32, the sensitivity of Nasometer ratings in correctly identifying the presence or absence of velopharyngeal areas in excess of 0.10 cm2 was 0.78 and 0.79, respectively. The sensitivity and specificity of nasometry in correctly identifying subjects with more than mild hypernasality in their speech was 0.89 while the specificity was 0.95. The results suggest that the Nasometer is an appropriate instrument that can be of value in assessing patients suspected of having velopharyngeal impairment.

A preliminary investigation concerning the use of nasometry in identifying patients with hyponasality and/or nasal airway impairment.

A series of 76 patients referred for evaluation at the Oral-Facial and Communicative Disorders Program was studied in an attempt to determine the extent to which acoustic assessments of speech, made utilizing a Kay Elemetrics Nasometer, corresponded with clinical judgments of hyponasality and aerodynamic measurements of nasal cross-sectional area. Among the 38 adults, the sensitivity of Nasometer ratings in correctly identifying adult subjects with moderate to severe nasal airway impairment was 0.38, whereas the specificity was 0.92. Comparable analyses for the group of 38 children were not possible because of the extent to which nasal airway size varies up to the age of 15 years. Among the entire group of patients, the sensitivity and specificity of nasometry in correctly identifying the presence or absence of hyponasality was 0.48 and 0.79, respectively. However, when patients with audible nasal emission were eliminated from analysis, the sensitivity rose to 1.0 and the specificity rose to 0.85. Possible reasons for the findings obtained and their clinical significance are discussed.