Nasal Air Flow During Normal Speech Production AMY E. THOMPSON, M.S. THOMAS J. HIXON, Ph.D. Tucson, Arizona 85721 Nasal air flow was measured during the speech of 112 normal subjects (59 females and 53 males) ranging in age from three years to 37 years, six months. Flow was zero during nearly all oral consonant and vowel utterances, suggesting that velopharyngeal closure was air-tight. Flow occurred during all nasal consonants and during vowels adjacent to nasal consonants. Both age and sex effects were demonstrated for flow on vowels preceding nasal consonants. These effects were interpreted as showing that progressively older subjects and female subjects demonstrate earlier anticipatory coarticulation in prepara- tion for forthcoming nasal consonants. Introduction is not to be expected in normal speakers (Nus- The velopharyngeal mechanism is a me- baum, Foley, and Wells, 1935; Moll, 1962; chanical valve situated between the oral and Van den Berg, 1962). nasal portions of the upper airway. Its control The second question inquires into the pos- of oral-nasal coupling accomplishes two im- sibility of a developmental schedule for gain- portant things in normal speech production: ing control over the velopharyngeal-closure one, it enables the development of oral air mechanism. The impetus for this question is pressure and air flow sufficient to produce the lack of information pertinent to this topic many of the consonants of speech, and two, it and the fact that several motor-speech behav- enables the generation of voice perceived to iors continue to be refined toward adultlike be free of hypernasal quality. Despite the standards well after normal speech is acquired recognized importance of normal velopharyn- and sometimes as late as 11 to 12 years of age geal function, many of the details of such (Kent, 1976). function remain to be specified. The present The third question of importance to the study is one of a series of studies being con- present investigation is an inquiry as to the ducted in the Department of Speech and possible existence of a sex difference with Hearing Sciences at the University of Arizona respect to control of the velopharyngeal-clo- to provide needed information about velopha- sure mechanism. A paucity of information ryngeal function in normal speech produc- exists in this regard, although that which is tion. available (McKerns and Bzoch, 1970) would Three questions are of central importance lead one to believe that there could be differ- in this part of this series of studies. The first ences in function between the sexes based on concerns the extent to which air-tight velo- differences in velopharyngeal structure. __ pharyngeal closure is characteristic of so- The general design of the present investi- called phonetically-oralized speech elements. gation involved an attempt to address these The impetus for this question is the belief that three questions through the measurement of is commonly held by many individuals that nasal air flow during the speech of a large complete closure of the velopharyngeal port group of males and females whose ages were distributed over a wide range. More specifi- cally, subjects were selected to encompass a The authors are affiliated with the University of Ari- range extended downward to the youngest zona, Tucson, Arizona. Dr. Hixon is a Professor in the age at which standard tasks could easily be Department of Speech and Hearing Sciences. This work was supported by Research Grant NS- performed and extended upward into middle- 09656 from the National Institute of Neurological and aged adulthood. Flow was selected as the Communicative Disorders and Stroke. method for studying velopharyngeal function 412 Thompson and Hixon, Nasar FLow 413 because of the simplicity of its measurement and the resulting analog of the speech signal and because, for the purposes of answering was displayed on the second channel of the the questions mentioned above, it constituted storage oscilloscope. When it was deemed nec- a sufficient tool for the study of normal speak- essary to record data permanently, displays ers (Warren, 1967). on the screen of the oscilloscope were photo- graphed with a Polaroid camera. For certain Method activities, an electronic metronome was used Suspects. One hundred twelve individuals to aid subjects in the pacing of their speech. served as subjects. Ninety-two of these sub- SpEECH SAMPLE. Utterance tasks consisted jects, 49 females and 43 males, ranged in age of three groups of activities: sustained pro- from three to 18 years. Ages were distributed ductions, syllable repetitions, and nonsense relatively evenly so that at least one subject, productions embedded in a carrier phrase. and usually more than one, fell within each Sustained productions included individual four-month interval within this age range. utterances of /i/, /s/, /z/, and /n/ at normal Typically, subjects of both sexes were in- conversational pitch, loudness, and quality. cluded within each interval. The remaining Each utterance was made following an inspi- persons studied were 20 adults, ten of each ration of about twice normal depth and lasted sex, ranging in age from 18 years, two months, for about five seconds. Syllable repetitions to 37 years, six months. Most of these subjects included productions of /ti/, /di/, /si/, /zi/ were less than 25 years of age. All 112 subjects and /ni/, each in trains of seven utterances, were selected to meet the following criteria: made at normal conversational pitch, loud- normal speech and voice commensurate with ness, and quality, with equal stress on each age, hearing reported to be within normal syllable, and at an utterance rate of three per limits, no known structural or neurological second. Nonsense productions included the disorders, and no known respiratory infections vowel-consonant-vowel (VCV) combinations or allergies at the time of testing. All subjects /iti/, /idi/, /isi/, /izi/, and /ini/ in the carrier were monolingual English speakers living in phrase "Say ___ again," produced at con- Tucson, Arizona. versational pitch, loudness, and quality, with EquiprmEnt. Two aspects of speech produc- normal prosody, and with stress placed on the tion were recorded: nasal air flow (hereinafter second vowel in the VCV. Each of the sus- referred to as flow) and the acoustic pressure tained productions and syllable repetition wave (hereinafter referred to as the speech trains were performed three times in succes- signal). Flow was channeled through an in- sion and each of the VCV productions was dividually-custom-formed mask placed over performed in a separate carrier phrase three the nose. Masks were made of Dux-seal, a times in succession. Utterances included in relatively compliant, clay-like material. Flow the study were chosen to encompass a variety from the mask was sensed by a double-coned, of phonetic contexts that could be executed two-square inch, Silverman-type, pneumo- easily by the younger subjects. Design of the tachometer coupled to a differential air-pres- sample was also guided by a desire to include sure transducer. The output analog voltage of a variety of manners of consonant production the latter was amplified, and the resulting (plosive, fricative, and nasal), and to include signal was low-pass filtered through a system voicing contrasts for cognate pairs. A single with a sharp roll-off that markedly attenuated place of consonant and vowel production was the signal above 20 Hz. The conditioned-flow chosen, namely, lingua-alveolar. This place analog was displayed on one channel of a had the advantage of avoiding lip gestures two-channel storage oscilloscope. The flow that would interfere with the seal formed by analog was calibrated through use of a con- the nasal mask. The high vowel /i/ was se- tinuously-variable flow pump whose output lected for study within the front vowel series was directed through a rotameter and the because of its presumed stringent velopharyn- pneumotachometer in series. The speech sig- geal-closure requirements (Moll, 1962), a fac- nal was sensed by a condenser microphone tor we considered important for insuring the positioned approximately six inches below strength of a target behavior were a develop- and to the front of the subject's lips. The mental schedule to be manifested. The utter- output from the microphone was amplified ance rate of three per second was found in a 414 Cleft Palate Journal, October 1979, Vol. 16 No. 4 pilot study to be the maximum rate at which all 333 sustained productions of /n/ involved very young subjects could perform reliably. nasal flow. Criterion scores were computed ProcEpURrE. Each subject was seated up- for each of the subjects as the mean peak flow right and positioned so that the screen of the on the three /n/-productions. The resulting oscilloscope was out of the visual field. A mask scores for the subject group yielded a mean was molded for the nose and was positioned value of 98.9 cc/sec, with a range of 23.3 cc/ on the subject. Each mask formed a small sec to 246.7 cc/sec, and a standard deviation tube, the proximal end of which fitted airtight of 38.1 cc/sec. Perusal of the criterion score against the upper lip and mid-facial region data for /n/ revealed no indication that nasal surrounding the nose. Care was taken to in- flow was related either to the age or to the sex sure that the walls of the mask did not block of the subjects studied. the external nares or contact the nasal alae. SyLLABLE ReEpPETITIONS. The syllables /ti/, Next, the microphone was positioned, and the /di/, /si/, /zi/, and /ni/, each performed in subject was instructed to repeat each utter- trains of seven, comprised the group of sylla- ance produced by an investigator. The model ble repetitions. The middle three repetitions utterances for the subjects met the criteria in each train were selected for analysis.