Fairbanks, Grant. Experimental Phonetics – T24

An Acoustical Study of the Pitch of
Infant Hunger Wails *1

Grant Fairbanks 12

This paper reports an acoustical investigation of the
pitch of experimentally induced hunger wails 23 produced
by the author's male infant. In brief, the experimental
situation was this: On the consecutive monthly birth
dates for the first 9 months of life the regular 2 o'clock
afternoon feeding period was withheld, the infant was
brought into the recording laboratory and placed before
the microphone. After wailing vocalization was approximately
continuous, a condition which was reached between
15 minutes and 1½ hours after placement before
the microphone, a 4-minute phonograph recording was
cut. This recording was subjected to acoustical measurement.

The characteristics of the infant show him to have
been a suitable subject for this type of experimentation.
The delivery was full-term, normal and easy. The birth
weight was 7½ pounds, which is approximately average
for male infants in the Middlewest. According to a periodic
series of anthropometric and psychological measurements
made by the Child Welfare Research Station and
the Department of Pediatrics at the State University of
Iowa, which measurements will not be presented in detail,
the infant grew and developed within the average
range. He was breast-fed, had no digestive disturbances,
and, in fact, no illnesses of any kind during the entire
9-month period of measurement. Of especial pertinence
to this study is the fact that he rarely cried, and, in general,
gave every superficial evidence of being an unusually
comfortable and happy infant. It should be emphasized
that on none of the 9 recording occasions was he
wailing at the time of being brought into the laboratory.

Acoustical analysis of the pitch of the recorded hunger
wails was accomplished by means of an instrument
for phonophotography and fundamental frequency measurement
from phonograph recordings, most recently
described by Cowan (2). The over-all error of this
method of frequency measurement is approximately 0.5
per cent, or 0.04 tone. Within each 4-minute recording,
6 equally spaced, 10-second intervals were photographed,
supplying for measurement, thus, 60 seconds from each
recording, a total of approximately 9 minutes for the
entire period. 34

I. Results

Figure 1 presents graphs of frequency distributions of
the pitches used. These are similar to conventional frequency
polygons, except that the variable being measured
is shown along the vertical axis which is the equal-tempered
musical scale. The abscissa, in the case of each
distribution, is percentage of cases, making the distributions
mutually comparable as to shape. The means are
indicated by horizontal lines. A composite distribution
of all pitches measured during the entire 9-month period
is shown at the left, while distributions for the consecutive
monthly measurements comprise the balance of
the figure. In Table 1 are presented the data computed
from the distributions.

The major results of the study, which may be observed
in Figure 1 and Table 1, fall into two divisions; 1) the
general pitch characteristics of the wails; 2) changes in
these characteristics during the time interval considered.

General Pitch Characteristics of the Hunger Wails

The mean of the composite distribution is seen to be
556 cycles per second. This is more than one octave
higher than the central tendency of the average adult
female speaking voice, and more than two octaves higher
than that of the average adult male.

The lowest frequency measured during the entire period
was 63 c.p.s., approximately two octaves below middle
C. Values this low are reasonably common in average201

image age in months | composite

Figure 1. Frequency distributions of the pitches used.

adult male speech, and it is not unusual for concert
basses to sustain such tones. In fact, some choral basses
are reported to be capable of singing tones one octave
lower. It is somewhat surprising, however, to discover
frequencies of this order produced by an immature infant
larynx. It should be pointed out that this is not one isolated
measurement, but that the distribution is more
or less continuous from the mean down (see Figure 1).

At the upper end of the distribution the highest frequency
measured was 2631 c.p.s. This tone is approximately
one octave higher than the top notes sung by such
a coloratura soprano as Lily Pons in the Bell Song, the
Quartet from Rigoletto, etc. Very few singers have been
reported to be capable of singing tones of the frequency
measured, more than 3 octaves above middle C.

These extreme values, encompassing, as has been
shown, the lowest notes of the bass and the highest notes
of the coloratura, provide a total range during the period
of 32.6 musical tones, or somewhat in excess of 5
octaves. This may be compared to the maximum singing

Table 1. Measurements of frequency and pitch

range of the adult, usually found to be in the neighborhood
of 18 to 20 tones, or approximately 3 octaves,
on the average.

Chances in the Pitch Characteristics
of the Hunger Wails

Inspection of the monthly means in Figure 1 and
Table 1 shows that there is a rapid and consistent rise
throughout the first half of the period, followed by irregular
but smaller changes thereafter, which form what
might be termed a plateau at this higher level. It will
be noted that these changes in central tendency cover
the wide range of 6.7 tones, or more than one octave.
The shape of the distributions is also seen to change.
From a comparatively normal distribution at one month,
the variability is seen to increase and the distributions to
become more irregular. Again this change is rapid
throughout the first half of the period. Attention should
be called to the rather prominent secondary peaks to be
seen at the upper ends of the distributions during the
last part of the period.

In order to assist visualization of the changes, four of
the measures from Table 1 are graphed in Figure 2.
The top curve of variations in the mean pitch level
shows the positively accelerated rise followed by the
plateau, features which have been described above. The
second curve, that of the total pitch range, is seen to
vary somewhat sporadically. Because this unreliable
measure of variability is affected by a few isolated cases,
the data plotted in the third curve were computed. This
measure, which has been termed the “90 per cent pitch
range,” is, for any given sample, the range of pitch which
subtends the median 90 per cent of the cases. In other
words, it is the difference between the ninety-fifth and
the fifth percentiles of the frequency distribution. The
variations in this measure are seen to be more regular,
and to be not dissimilar to the variations of the mean.
The changes in the standard deviation, shown in the
fourth curve, are observed to correspond even more
closely to the variations of the mean.

In summary, the changes during the first 9 months
were found to consist of 1) a large and rapid rise in the
central tendency of the pitches used during the first half
of the period, followed by a more or less consistently high
level thereafter; 2) concomitant changes in pitch variability.

II. Discussion

The available data afford no basis for the restrictive
selection of any single factor, or group of factors, as responsible
for these changes in the hunger wails. It is
known that the growth of the larynx during the first
year of life is normally very rapid, probably more rapid
than during any other post-natal year, with the possible
exception of the fifteenth in the male. There is no
reason to believe that the subject of the present study is
markedly different from the average infant in this respect.
Presumably a feature of the laryngeal growth is
an increase in the length and thickness of the vocal folds,
a change which accompanies normal pre-adult growth.
Differences in these respects also distinguish male from
female larynges and are the major factors in the vocal

Figure 2. Variations in pitch characteristics during the nine-month period. A: Mean pitch level in tones above 16.35 c.p.s. B: Total pitch range
in tones. C: 90 per cent pitch range in tones. D: Standard deviation in tones.203

pitch differences between the sexes. Since, other variaables
constant, increases in length and thickness lower
the natural frequency of a vibrator, a progressive lowering
of the pitch level, as in the case of the change from
childhood to maturity, might be expected. Instead, as
has been shown above, the change in the central tendency
of the hunger wails was generally upward during
the first half of the period. In other words, the direction
of the observed change in pitch level was inconsistent
with the presumed change in length and thickness of
the vocal folds. As has been suggested, length and thickness
probably determined, or at least limited, the general
pitch level of the entire period; since presumably they
changed rapidly, their influence may not be overlooked
in an explanation of the vocal changes during the period.
However, in view of this inconsistency, it seems reasonable
to conclude, by elimination, that the observed
change in pitch level was primarily a function of variation
in vocal fold tension rather than of variation in
length and thickness.

If this analysis be accepted, then a progressive increase
in the tension of the laryngeal musculature during the
first half of the period may be inferred and requires explanation.
This increase might be related to certain
psychological conditions. Such conditions constant, however,
it might reflect simply an increase in the capacity
to exert muscular tension in and adjacent to the larynx.
This suggestion would be consistent with the fact that
the average infant undergoes very rapid neuro-muscular
development during the first half year of life, and it
would provide an explanation for the rise in pitch during
the first 5 months. It is not necessarily incompatible
with the approximate plateau during the balance of
the 9-month period. The latter might be interpreted to
result from marked negative acceleration of neuromuscular
development (which is believed to occur at
about that age) coincident with less negatively accelerated
continuation of dimensional growth. In a like manner
the changes in pitch variability may be explained.

Nevertheless, it would be difficult to defend an exclusively
growth-and-development interpretation. It may
have been observed that the curves depicting the pitch
changes are remarkably similar to previous plottings of
data secured during the establishment of conditioned
responses. This similarity does not prove, per se, that a
process of conditioning or learning was going on. In the
light of what is known of infant behavior, however, it is
not unreasonable to suggest this as a possibility. One
measure of the goodness of conditioning is the magnitude,
amplitude or vigor of the response. Anrep (1), for
example, measured the amount of salivary flow per unit
of time, while Hilgard and Marquis (4) and Hilgard
and Campbell (3) recorded the amplitude of reflex eyelid
movement. The measurements made in the present
study may be considered comparable in the field of vocal
response. 4 5Making allowance for variations in drive
(e.g., hunger), and for the fact that one subject only was
studied, the changes in vocal pitch are such as would be
predicted on a conditioning or learning hypothesis. It
may be added that conditioning phenomena, if present,
do not, of course, preclude such concurrent operation of
other variables as has been discussed above.

References

(1) Anrep, G. V. Pitch discrimination in the dog. J. Physiol.,
1920, 53, 367-385.

(2) Cowan, M. Pitch and intensity characteristics of stage
speech. Arch. Speech, 1936, Suppl., 1, 1-92.

(3) Hilgard, E. R., and Campbell, A. A. The course of acquisition
and retention of conditioned eyelid responses in
man. J. Exper. Psychol., 1936, 19, 227-247.

(4) Hilgard, E. R., and Marquis, D. G. Acquisition, extinction,
and retention of conditioned lid responses to light in
dogs. J. Comp. Psychol., 1935, 19, 29-58.204

1* Reprinted from Child Development, Vol. 13, 1942, pp. 227-32.

21 From the Department of Speech, State University of Iowa.

32 No brief is held for the description of the vocalizations as
“hunger wails,” nor does it seem to be fruitful to speculate
about the degree to which they reflected fear, anger, or any
other affective state. The term is used to refer conveniently to
the crying which occurred under the conditions described.

43 The process of measurement is laborious, and, if these samples
appear to be small, it may be mentioned that past studies
of speech have customarily measured intervals of from 4 to 30
seconds in duration. As a matter of fact, the data reported
above involved the individual consideration of more than
170,000 sound waves.

54 Vocal intensity might have been an even better measure of
the vigor of a vocal response, but the available recording equipment
was incapable of handling the extreme intensity range.