On Pubescent Voice Change in Males

On Pubescent Voice Change in Males Harry Hollien, Gainesville, Florida Summary: This review of adolescent voice change (AVC) in males is introduced by a brief historical overview of the area. That effort is followed by a summarization of those core studies which describe the AVC process in the normal boy. Although no new experiments are presented, a number of related investigations are organized into a cohesive base—one that permits development of an AVC model The model, then, can be employed to establish a reasonable description of the process by providing information about its initiation, duration, and completion. It also assists in establishing perspectives about pubescent voice change and a baseline for future research. Key Words: Adolescent voice change–AVC–Pubescence–Adolescence–Male voice change.

‘‘I now would like to add an acknowledgment to this article; one about our editor: Robert T. Sataloff, MD. He is to be commended, of course, for his fine development of our Annual Symposia and The Voice Foundation. But, more importantly, I would like to salute him for his superb effort in building the Journal of Voice into a publication of international stature. This important accomplishment is deserving of recognition. Indeed, one of the primary reasons I wrote this article (at 84 years of age) was to acknowledge his leadership. Please join me in commending him.’’ INTRODUCTION First, it should be made clear that there are three major groups who legitimately study pubescent voice change. One group is made up of the teachers who train and develop the singers, the second consists of medical and clinical specialists who provide a remedial response to difficulties experienced by these artists. The third, and newest, cadre are the scientists (voice and phonetic) who are interested in—and study—the normal process of pubescence and voice change. The essay to follow will focus on the work of the third group (of which the author is a member) in an attempt to pull the experiments on the normal process of adolescent voice change (AVC) into a cohesive core that will permit the structuring of a predictive model. It is recognized, however, that the other two groups have made important contributions to the understanding of this process and a number of them will be included in this review. Second, why just males? For one thing, the present author is a male and just as women are often interested in studying the behaviors of their sex; he cheerfully pleads guilty for being curious about what happens to members of his own cadre. Also, he still remembers the puzzlement he felt when, as a boy, he experienced singing soprano one day and, then, being only able to sing baritone at what seemed to be but a day later—that is, if one could characterize the sounds he made as ‘‘singing.’’ Additionally, the dramatic and (sometimes, anyway) seemingly haphazard vocal events that occur during male adolescence often are more challenging than the more orderly process found in females. Definitions The behavioral events to be considered here can be identified in many ways. Some of the more common names are pubescence, Accepted for publication January 14, 2011. From the Institute of Advanced Study of the Communication Processes, University of Florida, Gainesville, Florida. Address correspondence and reprint requests to Dr. Harry Hollien, Institute of Advanced Study of the Communication Processes, 63 Dauer Hall, University of Florida, Gainesville, FL 32601. E-mail: [email protected] Journal of Voice, Vol. 26, No. 2, pp. e29-e40 0892-1997/$36.00 Ó 2012 The Voice Foundation doi:10.1016/j.jvoice.2011.01.007

adolescence, and voice change. In response, it would appear useful to establish some common ground—and ‘‘definitions’’ seems to be a good place to start. By this means, it maybe possible to boil down the subsequent discussion to one which is both reasonable and has manageable boundaries. As would be expected, generalized definitions abound. We all have read or heard of many of them. Briefly, the process in general involves that developmental segment of life which occurs when the individual male changes his status from being a child to that of a young adult. Many transformations occur during this period, including somatic growth, maturation of the gonads, and emergence of secondary sexual characteristics. In addition, metabolic changes occur in parallel with those cited, as do shifts in psychological status and in other types of behavior.1 More to the point, ‘‘pubescence,’’ which literally means ‘‘to grow hairy,’’ is defined as that life stage when sexual status is changed and maturity is reached. Adolescence, on the other hand, can be defined as the period during which the characteristics associated with childhood shift to those of an adult. Although technically different, these two terms often are applied interchangeably.1 Moreover, the process is one that is recognized as (1) being quite complex, (2) involving not just a smooth general growth pattern but one that exhibits spurts and (3) being marked by varying physiological and psychological changes. The problem is that, although some of the correlates of adolescence have been established, others have not. What is needed, specifically, is better information about (1) the exact nature of these many changes, (2) when they start, (3) when they are complete, and (4) the interrelationships among them. Even more important, many of these events are not well understood when a boy is considered as an ‘‘individual.’’ Covering these many processes would involve a far greater task than could be (or should be) attempted in this modest essay. And, anyway, our common focus here is on the human voice and its properties. Thus, the primary effort will be on the effects of the pubescent process on a boy’s voice. It will be both on its overall function and on those events specific to the individual. One of the areas to be considered will be the (often) rapid lowering of speaking fundamental frequency (SFF or Fo). Even

e30 more to the point, the question will be asked if change in SFF should be viewed simply as one of the many mutations which occur during adolescence, or if it is in some way more fundamental to the process. That is, should voice change be of particular interest to us only because we are specialists involved in some aspect of laryngeal operation, or can it be employed to predict or describe pubescence in some manner? For example, is it possible that voice change could be used to accurately signal the initiation and completion of adolescence? Perhaps it can, perhaps not. Yet, there is indication that good information about voice can provide us with a better understanding of a number of human behaviors. Think not? Consider the patterns that can be seen in Figure 1. They demonstrate how human voice frequency (Fo) generally varies over life—and for both men and women. Here is an instance where fundamental frequency alone can be used to track, and explain to some extent, a specific human behavior. That is, these data can be used to provide one of the foundations for the male-female coalescence theory of aging.2 First, note that the SFF levels for adult men and women have been reasonably well established,3–10 and that the relationships also are clearcut—and for both sexes—with respect to old age.6,11–23 The same maybe said for children.24–32 Now, observe those portions of the curves where adolescence is represented. Here, it is found that Fo drops to some extent in females and dramatically in males. In turn, these changes provide the contrasts, seen in later life, where SFF shift brings members of the two genders back toward each other. Hence, Fo provides one of the relationships that define the coalescence theory. Can a similar relationship be established for pubescence?

FIGURE 1. Male-female SFF means and ranges as a function of age. Note the greater drop for males at puberty and the convergence of the male-female Fo trends for the elderly.

Journal of Voice, Vol. 26, No. 2, 2012

PERSPECTIVE A little background Almost any individual reading these words will have a reasonably good idea of where at least some of our interest in AVC originated and how those concerns were passed on down through the ages. For example, people engaged in training young singers have always had a keen interest in the pubescent process. So have medical and related caregivers. Moreover, very young singers—both individually and those in choral groups—have attracted people who simply enjoy listening to this type of musical performance. Indeed, enthusiasms of that kind reach back beyond recorded history. But what happened—‘‘back then’’—when children (especially boys) experienced AVC? Sometimes it didn’t matter, as other singers would emerge to replace those that were ‘‘lost.’’ In yet other cases, women simply took over the roles of soprano and alto. But, in some cultures, women were not allowed to perform, thereby creating a problem. So, what was the response (in that case) on the part of the decision-makers? Some groups pressured religious authorities to let women perform, some teachers worked to prolong the adolescents’ ability to sing in the higher registers, and others worked with tenors to develop their ‘‘falsetto.’’ Still others simply attempted to ‘‘remove’’ the effects of pubescence. That is, noting that most eunuchs retained their childlike phonational range even though their bodies otherwise attained various levels of maturity, certain individuals, in position to do so, engaged in the barbaric approach of countering voice change by castrating the child singer. After all, eunuchs had been serving as ‘‘guardians of the harem,’’ as chamberlains and in certain other political positions throughout history and in such places as Egypt, India, Persia, China, and Greece. So this practice developed in Europe and flourished there during the Baroque period (especially between the years 1600 and 1750) where it is said that as many as 70% of the operatic singers were castrati. Fortunately, this evil practice was largely eliminated in the 19th century partly through the efforts of enlightened lawmakers and partly by edicts of the Catholic Church. But, what about more modern times? Here, teachers of singing appear to have concentrated on doing the best they could with the material at hand (with reference to singers and prospective singers). Nonetheless, a number of them still struggled to understand the pubescent process and the nature of AVC. So did a number of physicians and therapists. However, the problems faced by all of these groups were manifold. Relevant technology was either nonexistent or very crude, at least, until after World War I. Moreover, teachers and clinicians had neither the time nor the training to carry out sophisticated research. On the other hand, many of the individuals within the cited groups were both intellectually capable and observant. Hence, generalizations about these processes began to emerge. To illustrate, consider some of the cadaveric work, which was conducted early in the 20th century. It permitted a better understanding—generally anyway—of the overall growth of the body and the larynx. Nonetheless, Kahane33,34 when reporting on his breakthrough work in the area, indicated that ‘‘only fragmentary data’’ resulted from all that effort. He

On Pubescent Voice Change in Males

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further suggested that most of it actually was drawn from general anatomical texts—with even Gedgowd35 and Klock36 (who ‘‘described’’ adolescent laryngeal growth) neglecting to provide very much useful detail. Practitioners of other types also were active during this period. Clinicians were especially interested in—and studied—such behaviors as (1) voice breaks (sudden shifts from-and-to the adult register), (2) ‘‘husky’’ voice (a condition sometimes found in the voices of males during change), and (3) mutational falsetto (ie, ‘‘the failure of a boy to change from the higher pitched voice of preadolescence to the lower pitched voice of adolescence and adulthood’’)37. As would be expected, singing teachers also were interested in these same vocal problems and made contributions to their understanding. However, it must be said that, although these issues are much better understood today than they were then, some controversy still exists relative to their actual source and the best method for treating them. As has been suggested, a substantial number of individuals among professional singing teachers have been interested and active in the area of voice change in youth and have endeavored to classify the various stages of adolescent voice (see below). They have done so especially in attempts to upgrade their teaching and to avoid damaging their pupils’ voices. Numerous systems were proposed during the early part of the 20th century. Some were insightful, others not very well structured—or, even, potentially damaging. This general effort was expanded after World War II when yet more useful information became available. Some of the leaders during this period provided insight and developed rather sophisticated concepts and/or systems.38–42 The cited trend appears to have somewhat peaked with Cooksey43 but actually it continues on into the current century.44

contrasted these same voice ‘‘measures’’ to three levels of (observed) pubic hair growth. Among other things, he was surprised to note that only four voice breaks were recorded during more than 85 hours of oral reading by his subjects. Although some useful insights into the voice change process were gained here, not all of Pedrey’s measures were quantitative; hence, the impact of his findings was a little diluted. Nonetheless, certain of the somatic data aided investigators such as Tanner45 in their contribution to the overall understanding of the area. A different approach was adopted by Curry.52 He drew on the ‘‘sectional’’ research design employed by earlier scholars as well as on technical progress that had occurred during the 1930s. The equipment he used, the phonellegraph,53–55 was one of the very earliest devices where the fundamental frequency of ‘‘cold running speech’’ could be measured accurately. Curry designed and carried out a study on groups of six each 10-, 14-, and 18-year-old males. He reasoned that the first group consisted of prepubescent boys, the second of boys ‘‘within’’ adolescence, and the last as consisting pretty much of young adults. Because the groups were small (obtaining phonellegraphic data, while accurate, was very labor intensive), they were very carefully selected to be both homogeneous and representative of their cultural group. Height, weight, Intelligence Quotient, and about a dozen measures of ‘‘vocal pitch’’ were obtained and reported. The three groups exhibited mean SFF levels of 270, 242, and 137 Hz, respectively. This effort made a signal contribution to the study of AVC if only on the basis of the classic display that can be seen in Figure 2. As maybe observed there, male pubescence can be typified over time in, at least, three general dimensions—ie, by increasing height and weight curves and a falling Fo curve. The project further solidified the ‘‘sectional’’ research pattern—one that many subsequent researchers would follow. What it did not do was answer the basic question about when AVC starts, when it ends, how long it takes, and most importantly, what variability occurs among boys. Worse yet, the labor-intensive aspect of the phonellegraph limited the extent of data collection, and it would be many years before efficient fundamental frequency trackers would become available. Hence, the limitations related to small subject groups

Harry Hollien

CURRENT RESEARCH Early breakthroughs It was not until after many centuries of effort, and thousands of publications, that real progress began to be made in the study of male pubescence and the vocal events associated with this phenomenon.45 The rapid rise of technology, plus the emergence of the scientific method, had a powerful influence on research during the period around World War II. What resulted was a marked upgrading of the quality of research. The publications shifted from being mostly anecdotal and subjective (there were exceptions, of course, for example Fournier46) to efforts that were more objective and databased.47–50 It was during that period when Pedrey51 attempted to respond to some of the basic problems facing investigators who were trying to discover when voice change started and when it ended. His approach was to observe 1014 boys (sorted into 1 year categories) between the ages of 11 and 16 years. He gathered data on such variables as perceived voice status (ie, subjective judgments of vocal characteristics as they appeared related to pre-, neo-, and postadolescence), height, weight, density of pubic hair, voice breaks, and so on. Some rather useful information resulted from this effort. For example, Pedrey compared subjects’ actual age to three classes of ‘‘voice maturity’’; he then

FIGURE 2. A figure summarizing the general shifts in male height, weight, and SFF as a function of age during puberty. HT, height; WT, weight.

e32 were numbered among the unintended consequences that so often accompany research of this type. An attempt to fill in a few of the blanks Post World War II was a period of chaos in the area of voice; indeed, there were but few phonatory relationships that were not open to dispute during that era. For example, a debate existed as to how the vocal folds basically operated to initiate phonation. So did another as to whether or not they were elongated for frequency change during phonation. Both of these disputes (and many others) had been going on for decades.48,56–62 Actually, the Moore and von Leden60 work adequately addressed the first of these issues, but it was not until 1960 that the debate about ‘‘vocal fold elongation’’ was resolved.63 Perhaps most surprising (and hard to believe) was that it was not until 1958 that Van Den Berg64 was able to provide a cohesive defense of the myoelastic-aerodynamic theory of phonation—one powerful enough to finally send the neurochronaxic theory and its followers into oblivion. The same kind of confusions existed in the domain of AVC. Of course, a number of investigators had been making contributions of various types,37,50,65–69 but it seemed reasonable that a follow up on both Pedrey’s and, especially, Curry’s work would be fruitful. Accordingly, the sectional model was used to generate some information as to how the AVC process might relate to race, climate, and even nutrition. The first of these studies contrasted blacks residing in the Southern part of the United States (ie, Waco, Texas) to Curry’s groups. Happenstance had a lot to do with both the initiation and the precision of this project.70 That is, the present author attended Boston University with a man who later became the President of the Paul Quinn College (an institution affiliated with the African Methodist Episcopal church). He renewed his friendship with that individual when appointed as the faculty at Baylor University (also in Waco). The possibility of replicating Curry’s work, but on southern blacks, came up during one of the lectures he gave at Paul Quinn, and the faculty at that institution provided the necessary expertise to make the project a success. Specifically, groups of six each 10-, 14-, and 18-years-old African-American males were assessed; their selection closely paralleled that of the white subjects studied by Curry. That is, a rigorous selection process was used, one where subjects were within two months of their respective birthday and were representative (ie, close to median) of their age groups with respect to (1) height, (2) weight, (3) reading ability, and (4) speaking ability. Comparisons among the obtained data can be found in Table 1, which summarizes the age, weight, height and mean Fo from both studies. While, it would appear that blacks experience voice change earlier than do whites (note especially their lower mean Fo at 14 years), the obtained results actually led to more questions than to answers. That is, did a racial factor actually exist or were the differences because of (1) climate, (2) nutrition, and/or (3) time (over 20 years had passed before the second study was initiated). In an effort to clarify the questions asked—rather than just obscure them, as this particular study may have done—the Hollien-Malcik team carried out two additional investiga-

Journal of Voice, Vol. 26, No. 2, 2012

TABLE 1. Comparisons of Northern White Boys (NW)52 Studied in 1940 and Southern Negro Boys (SN)70 Studied in 1962 Group

Age (mo)

Height (in)

Weight (lb)

Median Fo (Hz)

10-y olds NW SN

120 120

54 54

66 65

270 223

14-y olds NW SN

170 168

60 64

102 114

242 163

18-y olds NW SN

217 216

68 69

139 138

137 124

Note: Fo variability ¼ NW: 1.56 tones; SN; 1.51 tones.

tions.71,72 The first involved Southern white boys and the second Northern white boys; the groups (10-, 14-. 18-year olds) were selected on the basis of the same six rigorous criteria as were the first two. Hence, direct four-way comparisons could be made. The 10-year olds displayed no statistically significant variation for any of the somatic or frequency measures. However, the three groups studied in the 1960s were more like each other (and bigger) than were Curry’s boys. Moreover, and as can be seen in Table 2, the 1940 group of white boys exhibited SFF levels that were the highest of all groups—and the white boys studied in 1965 and 1967 were more like the AfricanAmericans. The data modestly suggested that accelerated maturation was occurring but about all that can be said is that all four groups of preadolescents (ie, the 10-year olds) exhibited generally childlike SFF. The 14-year olds presented a somewhat different picture. Again, no statistically significant differences were found among the groups but there was a slight trend for the three postwar groups to be bigger than Curry’s. And, as can be seen from Table 2, the ‘‘modern’’ white boys displayed SFF more in a class with the Southern blacks. However, the African-Americans still exhibited the lowest Fo. Even better evidence for accelerated maturation (if not racial differences) maybe found in Table 3, where the boys who started and/or had completed voice change

TABLE 2. Median Fundamental Frequency Levels (in Hz) of Six Subjects in Each of the Four Studies52,70–72 of Three Age Groups Study NWB-1 (1940) SNB (1962) SWB (1965) NWB-2 (1967)

10-y olds

14-y olds

18-y olds

270 223 248 237

242 163 199 189

137 124 128 —*

* An 18-year-old group was not considered necessary for the fourth study.

Harry Hollien

On Pubescent Voice Change in Males

TABLE 3. Number of 14-Year-Old Boys Who Have Not Started Pubescent Voice Change and Have Either Initiated or Completed It Group 52

NWB-1 (1940) SNB (1962)70 SWB (1965)71 NWB-2 (1967)72

Not Started

Initiated

Completed

5 1 2 2

1 3 2 2

0 2 2 2

are listed. This pattern also is in agreement with Pedrey’s51 estimates. Unfortunately, however, even when taken as a whole, this compilation of four data sets did not provide clear-cut answers to the questions posed about race, nutrition, and/or climate. Moreover, they did little to upgrade the information about the limits, details, and dimensions of pubescent voice change in the individual. A larger effort Influenced by Perello67 (J. Perello, Personal communication, June 1963, August 1964.), the data cited above, and the development of the present author’s electronic Fundamental Frequency Indicator (FFI), he and his group shifted focus. That is, they attempted to test the hypothesis that climate change might be a factor that exerts an external but important influence on AVC. However, before reviewing one of the very large studies that resulted (see below), a brief introduction to the FFI apparatus would appear useful. FFI73 was a system that continuously extracted SFF from recorded speech and analyzed the resulting (digital) frequency data. It did not sample Fo but rather measured the individual waves obtained from a series of first-stage, very sharp, low pass filters (ie, 75 dB per octave). The subsequent stages consisted of A/D converters, which monitored the filters and coupled only the lowest one containing energy to the output system. As maybe seen in Figure 3, the resulting display included a printed table of all measurements (by semitone interval) and a histogram. It also provided the geometric mean SFF in Hertz and semitone level as well as the standard deviation (SD) in semitones. Other useful measures and a series of built-in validity tests ensured accuracy. The processing of a one-minute speech sample took about 6 minutes, hence very large studies were possible.5,6,74 The investigation on AVC versus climate involved the collection of data on height, weight, mean Fo, and variability (SD in semitones) for 491 boys residing in four countries.74,75 They were equally divided (roughly) into five groups of 12-, 13-, 14-, 15-, and 16-year olds. Of the total, 150 were Swedish, 180 Dutch or Polish, and 161 Spanish. That threeway sort permitted data to be obtained on subjects from cold, temperate, and warm climates. Information concerning age, medical and vocal history, speech and hearing defects, speaking and singing training, and so on, was obtained on each volunteer and used in the selection process. The major factors studied were physical size and SFF. The speech materials were obtained by having each subject orally read a standard passage in his na-

e33 tive language. This phonatory performance was recorded and subsequently analyzed by FFI-8, a solid-state version of the original FFI. The data most relevant to this review are summarized in Table 4. When the obtained relationships are analyzed, the best that can be said of them is that the curves found in Figure 2 had been validated and somewhat enhanced. They did not appear to support the Luchsinger/Perello postulate that residence in warmer climates would lead to earlier voice change. Of course, it can be conceded that much of their original thinking was based on the emergence of menstruation in girls rather than on some sort of observation of boys. Nonetheless, their general hypothesis had been a logical one. It was just not supported by the data to be found in Table 4. Indeed, AVC seemed to occur earlier in those boys (ie, the Swedes) who were from a relatively cold climate and then from those (Dutch, Poles) residing in temperate domains. The Catalan boys from Spain tended to experience these changes later in life. Oddly enough, the three data sets showed fairly close pattern alignment if not the expected absolute levels—and some socioeconomic and cultural effects may have been present. In short, this large study provided a reasonable validation of some of the prior (and smaller) ones but little support for them with respect to either the environmental effects on the process or the developmental trends among the boys themselves. A SHIFT IN FOCUS Longitudinal approach It became apparent early on that, no matter how large and sophisticated the sectional research project might be, the critical information about AVC would be unattainable until more sophisticated research designs were carried out. Accordingly, a large longitudinal study of boys was proposed, funded (National Institutes of Health), and conducted. Although a number of interim reports—including attempts to develop an AVC model—were made public,76–78 an extensive review of the longitudinal data was not published until 1994.79 Basically, this project involved a large number of subjects drawn from a group of 10.5- to 11.5-year-old boys residing in Wichita, Kansas. All received physical, speech, and hearing tests as well as other assessments. Ultimately, 65 of them met all selection criteria and were included in the study. Specifically, they (1) had been born in the Mid-West region of the United States and resided there during their childhood, (2) exhibited a general American dialect, (3) were of middleclass socioeconomic status, (4) exhibited test scores placing them in average to above-average intelligence categories, (5) evidenced average-to-good speaking ability, (6) were in generally good health, and (7) were free from speech or hearing disorders. In all, 48 of the 65 selected completed the 5-year study. Data were gathered on all subjects for up to 6 years (ie, the grant period plus an extension). They were as follows: 1. Physical size: Height, weight, and six body dimensions. Laryngeal size measures (by means of soft tissue X-ray) had been proposed, but this procedure was not

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Journal of Voice, Vol. 26, No. 2, 2012

FIGURE 3. A printout from the FFI. The geometric mean of cold running speech is provided in Hertz and semitones and distribution variability (ie, standard deviation) in semitones. Note also the quantitative and graphic displays.

funded because of the potential that such radiation might be harmful to the boys. 2. Voice: The two major phonatory characteristics studied were SFF level/variability and phonational frequency range (PFR). As it turns out, the mean SFF measures provided the breakout data and will be featured in this review. 3. Other: Voice breaks, husky voice, and mutational falsetto also were tracked and noted, as were behavioral and general health factors.

The research team consisted of the principal investigator, a nurse, three research assistants, a speech pathologist (on call), and a technician. A physician provided the initial examinations and was then on call. All data were obtained in a comfortable laboratory; that is, excepting for the voice recordings, which were made in a sound-treated room. Laboratory quality microphones and tape recorders were used; they were calibrated before each set of trials. The SFF measures were obtained by having subjects read the ‘‘Rainbow Passage’’80 at a normal rate and energy level. Oral reading was selected to ensure that

Harry Hollien

On Pubescent Voice Change in Males

TABLE 4. Summary Table of 491 European Boys Between the Ages of 12 and 16 Years Group by Age Swedish 12 13 14 15 16

Number Height Weight Mean SD of Subjects (in) (lb) Fo (Hz) (st*) 29 33 28 33 27

59 63 64 67 70

90 107 108 121 138

220 206 182 168 128

4.4 4.7 5.2 5.2 5.0

59 62 64 68 69

87 97 110 122 131

270 246 219 169 145

3.6 3.8 4.3 4.7 5.0

59 61 64 66 68

93 110 119 129 135

347 254 254 222 212

4.1 4.7 5.5 6.0 5.9

150 Dutch and Polish 12 13 14 15 16

30 36 39 44 31 180

Spanish 12 13 14 15 16

24 39 34 25 39 161

The European boys were from four countries and placed in 1-year categories.74 * semitones

the speech materials analyzed were both constant across subjects and over time. The Fo level and variability data were obtained by use of FFI73; the PFR data by procedures outlined by Hollien et al81 As anyone who has conducted longitudinal research will attest, good record keeping (and data backup) was a challenge. It was especially difficult because most of the data were gathered, stored, and analyzed before the days of adequate computer support. Nevertheless, no important records were lost over the period this investigation took place. It will be remembered that the focus of this review is on the possibility that the details of voice change can be captured for individual boys and, if so, that they then will be useful to the understanding of AVC or, even, in documenting it. To a great extent, the validity of that concept was supported by the longitudinal investigation. Thus, SFF will be the dominant element in the discussion to follow. On the other hand, the reader may find other of the results useful (a more complete discussion about them can be found in the Journal of the Acoustical Society of America article79). But first, a short review of some of these ‘‘other’’ issues may provide a reasonable perspective for the AVC data. The somatic measures primarily confirmed those reported by many other authors. It was noted that (1) the boys grew

e35 more rapidly during the pubescent period than before or after, (2) they sometimes exhibited growth spurts, but (3) not much temporal specificity was possible. Second, voice breaks, huskiness of voice, and mutational falsetto also were tracked. Just as with Pedrey, Curry, and others, these events appeared to occur but rarely and, when they did, they were mitigated either by the passage of time or by the efforts of the speech pathologist. Finally, it had been hypothesized that Phonational Frequency Range (PFR) might be useful as a baseline indicator of AVC. Indeed, a number of investigators had attempted to quantify it for this purpose.46,65–67,77,78,82 But when the present data were assessed, the across-study patterns did not provide clearcut relationships. Of course, the differences in experimental procedure may account for some of this variance. Nevertheless, several authors have suggested that PFR maybe restricted during puberty. Indeed, a few of them postulate that PFR may even be reduced to a level which signals the presence of voice pathology. Their position in this regard was neither supported by the present data nor for that matter, by the opinions of several of the practitioners specializing in vocal music.41,83 On the other hand, the greatest PFR here was observed to occur during the adolescence process—ie, for the period of most rapid change in AVC. This finding may be due to the fact that some subjects phonated in two ‘‘voices’’ during that period (ie, partly in the oncoming adult register and partly in their prepubescent voice). These data are consistent with statements found in the general vocal music literature that during adolescence the lower Fo boundary for males drops at a faster rate than does the upper. The patterns in the present case (which are based on nearly 1000 trials) were found to be stable, and their internal consistency was as good as that reported by others.10,84 The data in expanded PFR ranges also is consistent with the position articulated by certain musicologists that a boy’s physiological range maybe somewhat extended during adolescence.41,85 Yet, these data, although possibly interesting, permit but little specification of AVC.

A MODEL BASED ON FUNDAMENTAL FREQUENCY The major contribution of the longitudinal project may now be addressed. That is, much of the research conducted by the present author, plus publications by other relevant specialists (see references), has led to the postulation that the Fo change parameter may serve to signal the start, extent, and completion of AVC. Materials from the longitudinal project now permitted this hypothesis to be assessed.79 They also could be used to determine if, indeed, there was some sort of a useful correlation between AVC and adolescence. As it turns out, the cited hypothesis appears to exhibit reasonable validity. That is, it was found that SFF plots could be used for the purpose of defining AVC. To accomplish this, and develop the relevant model, a set of basic criteria first had to be established. They may be best understood by reference to Figure 4 where the actual initiation, extent, and completion, of the cited process, can be seen

e36

FIGURE 4. Graphic display of SFF for a subject experiencing AVC. The onset can be identified by S and completion by E. AVC duration for this male was about 22 months.

illustrated by the data-plot of a representative subject. Although this particular example is for ‘‘N ¼ 1,’’ it should be stressed that, even though the slopes exhibited for the other boys varied in steepness (see below), the basic pattern seen in Figure 4 held for all of the subjects. To be specific, AVC onset (or ‘‘S’’ for start) can be identified as the SFF peak, which was preceded by a generally flat—albeit varying—pattern for a period of at least four months. This pattern then had to be succeeded by a decreasing SFF with a slope at a rate of approximately a semitone per month for a number of months (usually 6 months or more). This SFF pattern could be—and was—established as the ‘‘onset’’ criterion in the AVC model, and as stated, it was met by all subjects who initiated that process. It was also possible to identify the termination of AVC as follows. End or ‘‘E’’ was defined as that point occurring at the lowest measured fundamental frequency immediately preceding a period of general frequency stabilization. As a result, the AVC process was found to reflect a minimum downward shift of 8–12 semitones. Modest reversals were expected (but none were found in excess of about a semitone), and these minor inversions were identified in about a third of the subjects. The most common reasons for them appeared to be colds or vocal abuse (cheering, shouting, or singing), which occurred before the first of two runs (during the Fo decreasing phase) but not for the subsequent one. In short, it became possible to define AVC as that period occurring between the frequencies identified at points ‘‘S’’ and ‘‘E.’’ That is, the initiation, duration, and completion of AVC could be established for the subjects in the experiment, and the defining vector was shift in SFF.

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Age of onset Some of the relationships provided by the model should be useful. The first factor to consider is the age of AVC onset (Figure 5). Forty-five of the 48 subjects who completed this project were found to have initiated AVC by its end. The remaining three had not done so by 15.5 years of age. Of those 45 who did, the very first to initiate the process reached ‘‘S’’ at the age of 11 years and 7 months (ie, at 139 months). The mean age of onset for all subjects was approximately 161 months (or about 13.4 years) with a standard deviation of 10.4 months. The mean would have been a bit higher if the three subjects cited above could have been included in the distribution. In any event, the number of initiations peaked during the half year immediately following the mean and only 6% of the subjects had not initiated AVC by 15.5 years of age (ie, by the end of data collection). These data led to the postulate that, while occasionally boys may start AVC as early as 10.5 years of age or as late as 16.5 years, the majority will initiate the process sometime between the ages of 12.5 and 14.5 years. Further, it was noted that these data lacked a well-defined bell-shaped curve (Figure 5) even though this might have been evident if a very large population of boys could have been studied. To sum, the AVC initiations were spread out over 3.5 years and exhibited a variable pattern. Indeed, there were only four periods when as many as four boys started the process. Most of the relationships established by this analysis are consistent with those reported by investigators using a sectional approach even though theirs are not extensive enough to support a model. For example, the mean age of AVC onset, found to be approximately 13.5 years, compared favorably with metrics reported (or predicted) by most authors37,66,70–72,74,83 with the only marked exception being Curry.52 Also predictable was the generally observed range of onset (10–16 years). The wide variations found in this regard suggest that there is no specific age—or narrow range of ages—at which AVC onset can be judged normal or even typical.

FIGURE 5. Age of onset of AVC in months and years as reported in a longitudinal investigation.79 The first of the boys initiated onset at about 11.5 years; three additional boys had not initiated it until sometime after 15.5 years.

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On the other hand, the data from this investigation do not support opinions expressed by some practitioners that deviation from a restricted range of AVC onset times suggests the presence of a voice disorder. That is, efforts to establish vocal health or normalcy on the basis of the presumed appropriateness of perceived pitch86 maybe more difficult to establish than had been imagined previously. It also appears that suggestions that onset of male adolescent voice should occur between the ages of 13 and 14 years69,87 must be reassessed. It probably is more useful to postulate that most boys will initiate AVC somewhere between the ages of 12 and 15 years but that even the minority who start earlier or later may also have normal voices. AVC duration Data on the completion of AVC (coupled to the patterns found for its onset) provide information not only on just when the process ends but also about its duration. Even though, the data on AVC completion are not quite as dramatic as those for onset, they still support the model. In any case, while a few of the subjects had not completely finished the shift by project’s end, it can be estimated that adult SFF level, for most American boys anyway, can be expected within the 5-year time frame between the ages of 13 and 18 years. A range as extensive as this one was not expected and, hence, this maybe one of the several relationships, which have previously led to confusions about adolescence and AVC. It also may constitute an area where the model requires further testing. As stated, the longer than predicted time that the average subject took to complete AVC was a little unexpected. As maybe seen from Figure 6, the AVC durations, as exhibited by those boys who had fully completed the process (plus estimates for those for which they could be reliably identified), ranged from 8 to 37 months; the mean duration of AVC was approximately 18 months. These results are not at all consistent with the commonly held position that this process takes but 3–6 months to complete.37,50,65 Moreover, the experience of one particular subject underscores the argument that completion of AVC can take a very long period of time. It was possible to track the subject even though he had not completed AVC after the end of data collection. It took him over 3 years (ie, 37 months) to stabilize at 110 Hz even though his voice was clinically normal during the entire period. First, these rather long durations are a little difficult to resolve. Of course, some of the prior opinions about this relationship could have been based on small samples, incomplete data, or misinterpretations. Second, and on the other hand, it may be possible that the process was not noticed by the relevant professionals except during the period of maximum change. Rapid shifts are bound to attract attention. Third, the shift from one register to another is quite prominent in males (with reference to both SFF and quality) and may signal change. Fourth, the existence of ‘‘voice breaks,’’ or huskiness, observed in a few males also may have contributed to the cited opinions. While voice breaks, etc. probably do not last long, they undoubtedly are quite noticeable when they do occur. Anyway, the data obtained from this research are at odds with many of the previously

FIGURE 6. AVC duration in months as reported in a longitudinal study.79 The data are for the 35 subjects who had fully completed the process and the eight subjects where reliable estimates could be made. The data for the one subject who took 37 months are included but he is not shown in the figure. reported opinions. That is, the mean AVC duration of 18 months reported here contrasts with the traditional viewpoint that it occurs in males during a short period of time and any change lasting more than a year maybe pathological in nature. To sum, the SFF material provided by the longitudinal investigation79 answers some of the basic questions about AVC in normal boys. Most notably, a model is provided for assessing that nature of voice change in the individual; it provides critical details about both its maximum range (10.5–16.5 years) and most common range (12.5–14.5 years). It also provides specification about duration where the normal period can take over 3 years and exhibits a mean of 18 months. Those temporal values are greater than those commonly expected, yet do not signal the presence of voice disorders. In short, it should be possible to use the AVC model to better understand, and quantify pubescence. Indeed, it should provide a testable hypothesis as well as a base for future postulations and research. External support for the model Although endocrinological assays were not included among the protocols for the project reviewed above, it was possible to compare the AVC trends found there with certain data on hormonal shifts gathered by others.88–91 Of the number reviewed, it was Knorr et al,92 who best provided information about shifts in testosterone level related to adolescence. In turn, their data furnished external evidence useful in validating the AVC model. That is, their data could be adapted for direct comparison with the AVC trends from the 1994 study.79 Specifically, the cumulative testosterone function found in Figure 7 was adapted from the Knorr et al92 data on 22 subjects. The estimates were made by extending each subject’s curve (with reference to change in testosterone) to bisect the baseline level. These intersects could then be employed to predict age of pubescent onset. Although the range for the testosterone data is somewhat greater than that for AVC, the two curves are similar. Further, it should be noted that the slope of the AVC curve probably would more

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FIGURE 7. A contrast of two methods by which the initiation of puberty is identified; both are shown as cumulative frequency curves. The first one, which was derived from measures of voice frequency, is AVC. The other one tracks testosterone levels as shifts from their baseline. The curve at the center top was extrapolated by adding the theoretical voice data for the three boys who had not initiated AVC onset by the end of that study.

closely parallel that for the testosterone shift if the three subjects who had not initiated onset could have been included in the mix. In short, it can be argued that the testosterone data are consistent with those from the AVC study and, hence, this convergence tends to validate both. It appears, then, that the cohesiveness of the AVC model (onset, duration, termination) permit it to be used as a predictor of pubescent voice change—and, perhaps even for the pubescent process in general. OTHER ISSUES Research on AVC continues even though it still tends to be scattered among a number of issues. As in the past, many of the studies tend to cluster in two areas (1) voice disorders— especially those found in singers—associated with the presumed vocal instability, which may accompany pubescence and (2) the upgrading of the teaching of adolescent singers both on an individual basis and for choral performances. Just as in the past, the medical practitioners and therapists interested in the first of these problems tend to focus on pathology. As would be expected, they are somewhat less interested in the singers per se than with the possible presence of voice disorders, and what to do about them; a legitimate approach, of course. However, they also appear to suggest that although baseline data about the dimensions of the pubescent process (and/or voice change itself) would be useful, pathology is paramount—especially if it interferes with the development and/or quality of the subject’s singing voice. Good examples maybe found in several recent articles. In one of them,93 the research effort appeared to be focused on predicting AVC onset to establish when to look for, and treat, the voice disorders that accompany such mutation. Here, the voices of young singers were examined using a variety of (mostly medical) techniques. Perhaps detection of greater hoarseness, noise components, jitter, shimmer, and the like in the voices of young male singers

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can be used to signal the onset of voice change. On the other hand, it would appear just as likely that these conditions would result from other types of problems or occur after mutation (ie, at varying times after the onset of AVC). These authors also draw from earlier work94–96 in their attempts to code mutation, its onset, and possible acceleration. Nonetheless, although their contributions are important, they appear to revolve around maintaining the vocal health of adolescent performers. Note that Fuchs et al93 end their report by recommending that young singers receive batteries of medical examinations every 3 months during the period of possible mutation. On the other hand, the research reported in the present review involves the study of many hundreds of normal boys experiencing AVC, and it can be used to suggest that voice disorders in general are not common during that period of life. That is, it may be possible that the high vocal usage and stress, associated with performing, results in greater rates of vocal pathology among the boys seen by the cited authors than among populations of nonsingers. Perhaps, the data provided by the longitudinal AVC research, and the model associated with it, could supply reasonable normative values for use by medical professionals in their work with, and research on, young singers. The other general thrust involves research on the proper training of singers and some of the behavioral changes that constitute a challenge to voice teachers. Again, it might be helpful for investigators to use the normative data now available as a model upon which to base their classifications of pre-, neo-, and postadolescence. Some authors, of course, have already attempted to do so but have used older systems for this purpose. For example, Harries et al97 tried to develop classifications based on their work and by coupling Cooksey’s43,44 six-stage structure with Tanner’s91 five-stage pubertal maturity index. To be specific, they organized their research by means of the combined Tanner-Cooksey systems in an attempt to model the adolescent process. They were successful to some extent in doing so. That is, they were able to fit a portion of their singing and speaking Fo data into the somewhat different structures proposed by the other two investigators. Although they were not able to resolve all the necessary dimensions, their results appeared to permit them to better describe the pubescent process as it related to vocal dynamics. Finally, one line of inquiry that has seen a resurgence of interest recently is that involving gaps in the PFR that can be found in the voices of some adolescents.82,98,99 A similar phenomenon—ie, gaps between registers—has previously been reported in a large study on normal PFR.81 Although the two issues do not appear to result from parallel vocal operations or conditions, they do raise concerns for the vocal pedagogic effort. In the first instance, it is important for teachers to be alert to the problem in adolescent singers. In such case, they maybe able to help male performers, who are well within the AVC process (and have not left it), to cope with both the child’s singing register and that of the adult. It would seem here that the teacher and pupil could choose to focus on one ‘‘register’’ or the other. In any case, the problem is one that teachers have to deal with although it is not a permanent condition. Finally, the other issue—gaps between registers in the adult (ie, between the

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modal and falsetto registers)—may present a problem when the teacher attempts to increase the students’ singing range.

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A SUMMARY Although there are many issues to consider by those of us who are interested in the voices of adolescents—and many hundreds more for those dealing with pubescence in general—our specialty area is currently experiencing good closure on some of its enigmas. Treatment of many voice pathologies has coalesced and become much more sophisticated. The education of young singers exhibits progress at much the same level. The work in this area by Experimental Phoneticians (including Voice Scientists) also has resulted in good progress. Perhaps the concepts that were detailed throughout this essay, and culminated in a model for AVC, can serve as one basis for the next upgrade in at least some of the relevant areas. Certainly, the baseline data provided about the key aspects of male AVC should aid in the planning and conduct of research to be carried out by investigators in all three of the areas cited. It certainly should provide for better cohesion in future investigations. REFERENCES 1. Marshall WA, Tanner JM. Puberty In: Faulkner F, Tanner JM, eds. Human Growth, Vol 2. New York, NY: Plenum Press; 1986:171–209. 2. Hollien H. The normal aging voice In: Huntley RA, Helfer KS, eds. Communication in Later Life. Boston, MA: Butterworth-Heinemann; 1995: 23–40. chap 2. 3. Britto AI, Doyle PC. A comparison of habitual and derived optimal voice fundamental frequency values in normal young adult speakers. J Speech Hear Disord. 1990;55:476–484. 4. Fitch J, Holbrook A. Modal vocal fundamental frequency for young adults. Arch Otolaryngol. 1970;92:379–382. 5. Hollien H, Jackson B. Normative data on the speaking fundamental frequency characteristics of young adult males. J Phonetics. 1973;1: 117–120. 6. Hollien H, Shipp T. Speaking fundamental frequency and chronological age in males. J Speech Hear Res. 1972;15:155–159. 7. Hollien H, Hollien PA, DeJong G. Effects of three parameters on speaking fundamental frequency. J Acoust Soc Am. 1997;102:2984–2992. 8. Krook M. Speaking fundamental frequency characteristics of normal Swedish subjects. Folia Phoniatr (Basel). 1988;40:82–90. 9. Kuenzel HJ. How well does average speaking fundamental frequency correlate with height and weight? Phonetica. 1989;46:117–125. 10. Reich AR, Frederisckson RR, Mason JA, Schlauch RS. Methodological variables affecting phonological frequency range in adults. J Speech Hear Res. 1990;55:124–131. 11. Benjamin B. Frequency variability in the aged voice. J Gerontol. 1981;36: 722–726. 12. Brown WS Jr, Morris R, Hollien H, Howell E. Speaking fundamental frequency characteristics as a function of age and professional singing. J Voice. 1991;5:310–315. 13. de Pinto O, Hollien H. Speaking fundamental frequency characteristics of Australian women: then and now. J Phonetics. 1982;10:367–375. 14. Decoster W, Debruyne F. The aging voice: changes in fundamental frequency, waveform stability and spectrum. Acta Otorhinolayrngol Belg. 1997;51:105–112. 15. Harnesberger JD, Shrivastav R, Brown WS, Rothman HB, Hollien H. Speaking rate and fundamental frequency as speech cues to perceived age. J Voice. 2008;22:58–69. 16. Horii Y, Ryan W. Fundamental frequency characteristics and perceived age of adult male speakers. Folia Phoniatr (Basel). 1981;33:227–233. 17. Linville S, Fisher H. Acoustic characteristics of women’s voices with advancing age. J Gerontol. 1985;40:324–330.

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