D W Warren

University of North Carolina at Chapel Hill, Chapel Hill, NC, United States

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Publications (54)47.39 Total impact

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    ABSTRACT: The purpose of this study was to quantify perceived hypernasality in children. One-third octave spectra of the isolated vowel [i] were obtained from 32 children with cleft palate and 5 children without cleft palate. Four experienced listeners rated the severity of hypernasality of the 37 speech samples using a 6-point equal-appearing interval scale. When the average 1/3-octave spectra from the hypernasal group and the normal resonance group were compared, spectral characteristics of hypernasality were identified as increased amplitudes between F1 and F2 and decreased amplitudes in the region of F2. Based on the findings of the children's speech, 36 speech samples with manipulated spectral characteristics were used to minimize the influences of voice source characteristics on perceived hypernasality. Multiple regression analysis revealed a high correlation (R = 0.84) between the amplitudes of 1/3-octave bands (1 k, 1.6 k, and 2.5 kHz) and the perceptual ratings. Increased amplitudes of bands between F1 and F2 (1 k, 1.6 kHz) and decreased amplitude of the band of F2 (2.5 kHz) was associated with an increasing perceived hypernasality. These results suggest that the amplitudes of the three 1/3-octave bands are appropriate acoustic parameters to quantify hypernasality in the isolated vowel [i].
    The Journal of the Acoustical Society of America 06/2001; 109(5 Pt 1):2181-9. · 1.56 Impact Factor
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    ABSTRACT: The purpose of this study was to examine the influence of acoustic and perceptual factors of speech on listeners' perceived hypernasality in the vowel [i]. The isolated syllable [pi] produced by 22 children with hypernasal speech and 6 noncleft children was rated by 10 listeners. These speech samples were then divided into two groups: (1) the samples (n = 14) that received inconsistent ratings from each listener or variable ratings among listeners (i.e., unreliable ratings) and (2) the samples (n = 14) that received consistent ratings from each listener and similar ratings among listeners (i.e., reliable ratings). These results suggest that the severity of hypernasality was easy to rate in some speech samples and not in others. Voice quality deviation and a particular type of spectral change that related to the severity of hypernasality could be factors that influence perceived hypernasality.
    Folia Phoniatrica et Logopaedica 01/2001; 53(4):198-212. · 0.55 Impact Factor
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    ABSTRACT: The purpose of this study was to examine the influence of acoustic and perceptual factors of speech on listeners’ perceived hypernasality in the vowel [i]. The isolated syllable [pi] produced by 22 children with hypernasal speech and 6 noncleft children was rated by 10 listeners. These speech samples were then divided into two groups: (1) the samples (n = 14) that received inconsistent ratings from each listener or variable ratings among listeners (i.e., unreliable ratings) and (2) the samples (n = 14) that received consistent ratings from each listener and similar ratings among listeners (i.e., reliable ratings). These results suggest that the severity of hypernasality was easy to rate in some speech samples and not in others. Voice quality deviation and a particular type of spectral change that related to the severity of hypernasality could be factors that influence perceived hypernasality.
    Folia Phoniatrica et Logopaedica 01/2001; 53(4):198-212. · 1.08 Impact Factor
  • D J Zajac, D W Warren
    Journal of Speech Language and Hearing Research 01/2001; 43(6):1532-4. · 1.93 Impact Factor
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    ABSTRACT: Twenty healthy adults, age range 20-55 years, participated in a study to assess the responses of the upper airway to sudden, unanticipated pressure venting during speech production. A computer was used to open or close a valve in a random fashion during one of two productions of the word 'hamper'. The SAR System (Microtronics Corp., Chapel Hill, N.C., USA) was used to collect and monitor respiratory variables associated with speech production. Results indicated no significant changes in duration between vented and unvented conditions. Although intraoral pressure was reduced under vented conditions, the magnitude was sufficient for sound generation. Respiratory effort increased when the airway was suddenly vented, suggesting a compensatory response to experimental perturbation. However, the response contrasted somewhat from what has been observed in patients with velopharyngeal inadequacy, indicating that the strategy used may be different.
    Folia Phoniatrica et Logopaedica 02/1999; 51(6):250-60. · 0.55 Impact Factor
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    Robert Mayo, Donald W. Warren, David J. Zajac
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    ABSTRACT: The objective of this study was to determine the influence of velopharyngeal (VP) inadequacy on respiratory speech compensations. The pressure-flow technique was used to measure pressure, airflow, and timing variables associated with VP closure during the production of the initial plosive consonant /p/ in a series of the utterance "papa." The study was conducted in the speech and breathing laboratory of the UNC Craniofacial Center. Eighty-two subjects with cleft lip and/or palate were assessed. The subjects were divided into two groups, those with adequate VP closure (VP size <.010 cm2) and those with inadequate VP closure (VP size >0.10 cm2). The adequate group was comprised of 62 subjects, and 20 subjects were categorized as inadequate. Peak intraoral pressure decreased in the inadequate group, but the difference was not significant. Nasal airflow increased (p < .01), but duration of the pressure pulse was the same for both groups. The area under the pressure curve decreased for the inadequate group (p = .04). These data contrast with previously reported published data using /p/ in the utterance "hamper." This suggests that phonetic context influences the compensatory response to velopharyngeal inadequacy. Additionally, while the findings are somewhat similar to studies that involved noncleft subjects whose oral airway was suddenly vented during the production of /p/, there is enough difference to suggest that learning also affects the compensatory outcome.
    The Cleft Palate-Craniofacial Journal 07/1998; 35(4):299-303. · 1.24 Impact Factor
  • The Journal of the Acoustical Society of America 01/1998; 103(5). · 1.56 Impact Factor
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    ABSTRACT: The speech respiratory system is configured in ways that tend to maximize its ability to respond to changes in the airway environment. Intraoral pressures remain at levels sufficient to generate reliably recognized consonant sounds even in the presence of structural deficits such as velopharyngeal inadequacy. Similar respiratory compensations occur when bite blocks and bleed valves are used to vent airway pressures. The purpose of the present study was to determine the sensitivity of the monitoring system psychophysically and to assess its physiological response to sudden, unanticipated perturbations. Twenty adults were asked to produce the utterance/pa/, and a calibrated perturbator valve permitted air to escape from the oral cavity on randomly selected productions. Respiratory responses were recorded using PERCI-SARS instrumentation. The results indicated that sudden openings of 0.14 cm2 (SD = 0.04) were detected by speakers. Compensatory respiratory responses to suprathreshold pressure-venting occurred rapidly (i.e., 27 ms [SD = 8]) after valve opening. Although peak pressure and area under the pressure pulse fell with valve opening, the magnitude of pressure was nevertheless sufficient for sound generation. Measurements of the slope of the rise in intraoral pressure after subthreshold pressure-venting in 10 participants were compared to measurements obtained from an-elastic model of the upper airway. The data demonstrated a significant difference between vented and unvented conditions for the model, but not the participants. This suggests that elastic recoil is actively and unconsciously controlled in humans to compensate for losses in airway pressure during speech.
    Journal of Speech Language and Hearing Research 09/1997; 40(4):848-57. · 1.93 Impact Factor
  • Donald W. Warren, Robert Mayo, David J. Zajac, A H Rochet
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    ABSTRACT: Nasal resistance (NRZ) values for healthy adults range from 1.0 to 3.5 cm H2O/L/sec. Some oral breathing tends to occur at values above 3.5. The purpose of the present study was to determine at what level of NRZ individuals sense that nasal breathing is difficult. A diaphragm was used to add four different resistance loads in random to 15 adult subjects. These loads were 5,8, and 15 cm H2O/L/sec and a value 40% above the individual's normal NRZ. Loads were added under four conditions: normal breathing, fixed flow rate, fixed breathing rate, and fixed flow and breathing rate. The pressure-flow technique was used to measure NRZ under all conditions. The study revealed that the sensation of breathing difficulty occurred at a median resistance of 5 cm H2O/L/sec and, as subjects were constrained to maintain fixed flow and breathing rates, the magnitude of RZ, at which the sensation of dyspnea was noted, decreased. The values observed in this study support previous findings suggesting that individuals switch to some oral breathing to maintain an adequate level of upper airway resistance at values between 3.5 and 4.5 cm H2O/L/sec. The findings also show that individuals attempt to minimize increases in airway resistance by modifying breathing behaviors.
    The Cleft Palate-Craniofacial Journal 06/1996; 33(3):231-5. · 1.24 Impact Factor
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    ABSTRACT: 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.
    The Cleft Palate-Craniofacial Journal 04/1996; 33(2):143-9. · 1.24 Impact Factor
  • Donald W. Warren, Rodger M. Dalston, Robert Mayo
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    ABSTRACT: 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.
    The Cleft Palate-Craniofacial Journal 08/1994; 31(4):257-62. · 1.24 Impact Factor
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    Robert Mayo, Rodger M. Dalston, Donald W. Warren
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    ABSTRACT: 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.
    The Cleft Palate-Craniofacial Journal 08/1993; 30(4):397-400. · 1.24 Impact Factor
  • Donald W. Warren, Rodger M. Dalston, Robert Mayo
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    ABSTRACT: 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.
    The Cleft Palate-Craniofacial Journal 04/1993; 30(2):150-4. · 1.24 Impact Factor
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    ABSTRACT: 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.
    The Cleft Palate-Craniofacial Journal 08/1992; 29(4):330-5. · 1.24 Impact Factor
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    D W Warren, A P Rochet, R M Dalston, R Mayo
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    ABSTRACT: 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 Journal of the Acoustical Society of America 06/1992; 91(5):2947-53. · 1.56 Impact Factor
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    Hui Liu, Donald W. Warren, Rodger M. Dalston
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    ABSTRACT: 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 Cleft Palate-Craniofacial Journal 08/1991; 28(3):261-5; discussion 265-6. · 1.24 Impact Factor
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    ABSTRACT: 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.
    American Journal of Orthodontics and Dentofacial Orthopedics 08/1991; 100(1):59-65. · 1.44 Impact Factor
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    ABSTRACT: 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.
    The Cleft Palate-Craniofacial Journal 05/1991; 28(2):184-8; discussion 188-9. · 1.24 Impact Factor
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    ABSTRACT: The purpose of this study was to assess the oral response to severe nasal airway impairment in patients with cleft palate. Inductive plethysmography was used to measure the percent of nasal breathing, and the pressure-flow technique was used to estimate nasal area in 15 persons with severe nasal airway impairment. Mean nasal area was 0.17 cm2, and the average percent of nasal breathing was 20%. Analysis revealed a strong correlation (0.87) between nasal size and percent of nasal breathing in this selected group. Modeling studies based on the mean values from the subjects' data indicated that the model "mouth" would have to open 0.5 cm2 to shunt 80% of the airflow orally, an amount equivalent to the mean value of the subjects' respiratory mode. More important, the extrapolated data revealed that upper-airway resistance decreased in the model from 8.7 cm H2O/L/sec to a level of 3.2 cm H2O/L/sec, which is an average value for healthy adults. These data support the concept that the mouth acts as a variable resistor to maintain an optimal respiratory tract resistance when the nasal airway is impaired.
    American Journal of Orthodontics and Dentofacial Orthopedics 05/1991; 99(4):346-53. · 1.44 Impact Factor
  • R M Dalston, D W Warren, E T Dalston
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    ABSTRACT: 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.
    Journal of speech and hearing research 03/1991; 34(1):11-8.