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Disorders of voice may a¤ect up to 5% of children, and instrumental procedures such as acoustics, aerody-namics, or electroglottography (EGG) may complement auditory-perceptual and imaging procedures by provid-ing objective measures that help in determinprovid-ing the nature and severity of laryngeal pathology. The use of Instrumental Assessment of Children’s Voice 35

these procedures should take into account the devel-opmental features of the larynx and special problems associated with a pediatric population.

An important starting point is the developmental anatomy and physiology of the larynx. This background is essential in understanding children’s vocal function as determined by instrumental assessments. The larynx of the infant and young child di¤ers considerably in its anatomy and physiology from the adult larynx (see anatomy of the human larynx). The vocal folds in an infant are about 3–5 mm long, and the composition of the folds is uniform. That is, the infant’s vocal folds are not only very short compared with those of the adult, but they lack the lamination seen in the adult folds. The lamination has been central to modern theories of pho-nation, and its absence in infants and marginal develop-ment in young children presents interesting challenges to theories of phonation applied to a pediatric population.

An early stage of development of the lamina propria begins between 1 and 4 years, with the appearance of the vocal ligament (intermediate and deep layers of the lamina propria). During this same interval, the length of the vocal fold increases (reaching about 7.5 mm by age 5) and the entire laryngeal framework increases in size.

The di¤erentiation of the superficial layer of the lamina propria apparently is not complete until at least the age of 12 years.

Studies on the time of first appearance of sexual dimorphism in laryngeal size are conflicting, ranging from 3 years to no sex di¤erences in laryngeal size ob-servable during early childhood. Sexual dimorphism of vocal fold length has been reported to appear at about age 6–7 years. These reported anatomical di¤erences do not appear to contribute to significant di¤erences in vocal fundamental frequency ( f0) between males and females until puberty, at which time laryngeal growth is remarkable, especially in boys. For example, in boys, the anteroposterior dimension of the thyroid cartilage increases threefold, along with increases in vocal fold length.

Acoustic Studies of Children’s Voice. Mean f0has been one of the most thoroughly studied aspects of the pedi-atric voice. For infants’ nondistress utterances, such as cooing and babbling, mean f₀falls in the range of 300–

600 Hz and appears to be stable until about 9 months, when it begins to decline until adulthood (Kent and Read, 2002). A relatively sharp decline occurs between the ages of 12 months and 3 years, so that by the age of 3 years, the mean f₀ in both males and females is about 250 Hz. Mean f0 is stable or gradually falling between 6 and 11 years, and the value of 250 Hz may be taken as a reasonable estimate of f0in both boys and girls. Some studies report no significant change in f₀ during this developmental period, but Glaze et al. (1988) reported that f0decreased with increasing age, height, and weight for boys and girls ages 5–11 years, and Ferrand and Bloom (1996) observed a decrease in the mean, maxi-mum, and range of f₀ in boys, but not in girls, at about 7–8 years of age.

Sex di¤erences in f0emerge especially strongly during adolescence. The overall f₀ decline from infancy to adulthood is about one octave for girls and two octaves for boys. There is some question as to when the sex di¤erence emerges. Lee et al. (1999) observed that f0

di¤erences between male and female children were sta-tistically significant beginning at about age 12 years, but Glaze et al. (1988) observed di¤erences between boys and girls for the age period 5–11 years. Further, Hacki and Heitmuller (1999) reported a lowering of both the habitual pitch and the entire speaking pitch range be-tween the ages of 7 and 8 years for girls and bebe-tween the ages of 8 and 9 years for boys. Sex di¤erences emerge strongly with the onset of mutation. Hacki and Heit-muller (1999) concluded that the beginning of the muta-tion occurs at age 10–11 years. Mean f0 change is pronounced in males between the ages of about 12 and 15 years. For example, Lee et al. (1999) reported a 78%

decrease in f0 for males between these ages. No signifi-cant change was observed after the age of 15 years, which indicates that the voice change is e¤ectively com-plete by that age (Hollien, Green, and Massey, 1994;

Kent and Vorperian, 1995).

Other acoustic aspects of children’s voices have not been extensively studied. In apparently the only large-scale study of its kind, Campisi et al. (2002) provided normative data for children for the parameters of the Multi-Dimensional Voice Program (MDVP). On the majority of parameters (excluding, of course, f₀), the mean values for children were fairly consistent with those for adults, which simplifies the clinical application of MDVP. However, this conclusion does not apply to the pubescent period, during which variability in ampli-tude and fundamental frequency increases in both girls and boys, but markedly so in the latter (Boltezar, Bur-ger, and Zargi, 1997). It should also be noted voice training can a¤ect the degree of aperiodicity in children’s voices (Dejonckere et al., 1996) (see acoustic assess-ment of voice).

Aerodynamic Studies of Children’s Voice. There are only limited data describing developmental patterns in voice aerodynamics. Table 1 shows normative data for flow, pressure, and laryngeal airway resistance from three sources (Netsell et al., 1994; Keilman and Bader, 1995; Zajac, 1995, 1998). All of the data were collected during the production of /pi/ syllable trains, following the procedure first described by Smitheran and Hixon (1981). Flow appears to increase with age, ranging from 75–79 mL/s in children aged 3–5 years to 127–188 mL/s in adults. Pressure decreases slightly with age, ranging from 8.4 cm H₂O in children ages 3–5 years to 5.3–6.0 cm H2O in adults. Laryngeal airway pressure decreases with age, ranging from 111–119 cm H₂O/L/s in children aged 3–6 years to 34–43 cm H2O/L/s in adults. This decrease in laryngeal airway pressure occurs as a func-tion of the rate of flow increase exceeding the rate of pressure decrease across the age range.

Netsell et al. (1994) explained the developmental changes in flow, pressure, and laryngeal airway pressure

as secondary to an increasing airway size and decreasing dependence on expiratory muscle forces alone for speech breathing with age. No consistent di¤erences in aero-dynamic parameters were observed between female and male children. High standard deviations reflect consid-erable variation between children of similar ages (see aerodynamic assessment of voice).

Electroglottographic Studies of Children’s Voice. Al-though EGG data on children’s voice are not abun-dant, one study provides normative data on a sample of 164 children, 79 girls and 85 boys, ages 3–16 years (Cheyne, Nuss, and Hillman, 1999). Cheyne et al.

reported no significant e¤ect of age on the EGG mea-sures of jitter, open quotient, closing quotient, and opening quotient. The means and standard deviations (in parentheses) for these measures were as follows: jit-ter—0.76% (0.61), open quotient—54.8% (3.3), closing quotient—14.1% (3.8), and opening quotient—31.1%

(4.1). These values are reasonably similar to values reported for adults, although caution should be observed because of di¤erences in procedures across studies (Takahashi and Koike, 1975) (see electroglotto-graphic assessment of voice).

One of the most striking features of the instrumental studies of children’s voice is that, except for f₀ and the aerodynamic measures, the values obtained from instru-mental procedures change relatively little from child-hood to adultchild-hood. This stability is remarkable in view of the major changes that are observed in laryngeal anatomy and physiology. Apparently, children are able to maintain normal voice quality in the face of consid-erable alteration in the apparatus of voice production.

With the mutation, however, stability is challenged, and the suitability of published normative data is open to question. The maintenance of rather stable values across a substantial period of childhood (from about 5 to 12 years) for many acoustic and EGG parameters holds a distinct advantage for clinical application. It is also clear

that instrumental procedures can be used successfully with children as young as 3 years of age. Therefore, these procedures may play a valuable role in the objective as-sessment of voice in children.

See also voice disorders in children.

—Ray D. Kent and Nathan V. Welham

References

Boltezar, I. H., Burger, Z. R., and Zargi, M. (1997). Instability of voice in adolescence: Pathologic condition or normal developmental variation? Journal of Pediatrics, 130, 185–

190.

Campisi, P., Tewfik, T. L., Manoukian, J. J., Schloss, M. D., Pelland-Blais, E., and Sadeghi, N. (2002). Computer-assisted voice analysis: Establishing a pediatric database.

Archives of Otolaryngology–Head and Neck Surgery, 128, 156–160.

Cheyne, H. A., Nuss, R. C., and Hillman, R. E. (1999). Elec-troglottography in the pediatric population. Archives of Otolaryngology–Head and Neck Surgery, 125, 1105–1108.

Dejonckere, P. H. (1999). Voice problems in children: Patho-genesis and diagnosis. International Journal of Pediatric Otorhinolaryngology, 49(Suppl. 1), S311–S314.

Dejonckere, P. H., Wieneke, G. H., Bloemenkamp, D., and Lebacq, J. (1996). F0-perturbation and f0-loudness dynam-ics in voices of normal children, with and without education in singing. International Journal of Pediatric Otorhino-laryngology, 35, 107–115.

Ferrand, C. T., and Bloom, R. L. (1996). Gender di¤erences in children’s intonational patterns. Journal of Voice, 10, 284–

291.

Glaze, L. E., Bless, D. M., Milenkovic, P., and Susser, R.

(1988). Acoustic characteristics of children’s voice. Journal of Voice, 2, 312–319.

Hacki, T., and Heitmuller, S. (1999). Development of the child’s voice: Premutation, mutation. International Journal of Pediatric Otorhinolaryngology, 49(Suppl. 1), S141–S144.

Hollien, H., Green, R., and Massey, K. (1994). Longitudinal research on adolescent voice change in males. Journal of the Acoustical Society of America, 96, 2646–2654.

Table 1. Aerodynamic normative data from three sources: N (Netsell et al., 1994), K (Keilman & Bader, 1995), and Z (Zajac, 1995, 1998). All data were collected using the methodology described by Smitheran and Hixon (1981). Values shown are means, with standard deviations in parentheses

Reference

Age

(yr) Sex N

Flow (mL/s)

Pressure (cm H2O)

LAR (cm H2O/L/s)

N 3–5 F 10 79 (16) 8.4 (1.3) 111 (26)

N 3–5 M 10 75 (20) 8.4 (1.4) 119 (20)

K 4–7 F&M 7.46 (2.26)

N 6–9 F 10 86 (19) 7.4 (1.5) 89 (25)

N 6–9 M 9 101 (42) 8.3 (2.0) 97 (39)

Z 7–11 F&M 10 123 (30) 11.4 (2.3) 95.3 (24.4)

K 8–12 F&M 6.81 (2.29)

N 9–12 F 10 121 (21) 7.1 (1.2) 59 (7)

N 9–12 M 10 115 (42) 7.9 (1.3) 77 (23)

K 13–15 F&M 5.97 (2.07)

K 4–15 F&M 100 50–150 87.82 (62.95)

N Adult F 10 127 (29) 5.3 (1.2) 43 (10)

N Adult M 10 188 (51) 6.0 (1.4) 34 (9)

F¼ female, M ¼ male, N ¼ number of participants, LAR ¼ laryngeal airway resistance.

Instrumental Assessment of Children’s Voice 37

Keilman, A., and Bader, C. (1995). Development of aerody-namic aspects in children’s voice. International Journal of Pediatric Otorhinolaryngology, 31, 183–190.

Kent, R. D., and Read, C. (2002). The acoustic analysis of speech (2nd ed.). San Diego, CA: Singular/Thompson Learning.

Kent, R. D., and Vorperian, H. K. (1995). Anatomic develop-ment of the craniofacial-oral-laryngeal systems: A review.

Journal of Medical Speech-Language Pathology, 3, 145–190.

Lee, S., Potamianos, A., and Narayanan, S. (1999). Acoustics of children’s speech: Developmental changes of temporal and spectral parameters. Journal of the Acoustical Society of America, 105, 1455–1468.

Netsell, R., Lotz, W. K., Peters, J. E., and Schulte, L. (1994).

Developmental patterns of laryngeal and respiratory func-tion for speech producfunc-tion. Journal of Voice, 8, 123–131.

Smitheran, J., and Hixon, T. (1981). A clinical method for es-timating laryngeal airway resistance during vowel produc-tion. Journal of Speech and Hearing Disorders, 46, 138–146.

Takahashi, H., and Koike, Y. (1975). Some perceptual dimen-sions and acoustical correlates of pathological voices. Acta Otolaryngolica Supplement (Stockholm), 338, 1–24.

Zajac, D. J. (1995). Laryngeal airway resistance in children with cleft palate and adequate velopharyngeal function.

Cleft Palate–Craniofacial Journal, 32, 138–144.

Zajac, D. J. (1998). E¤ects of a pressure target on laryngeal airway resistance in children. Journal of Communication Disorders, 31, 212–213.