Harvard Psychological Studies Part 54

Hensen[16] first turned the phonautograph to account for the study of speech. He used a diaphragm of goldbeater's skin, of conical shape, with a stylus acting over a fulcrum and writing on a thinly smoked gla.s.s plate. The apparatus was later improved by Pipping, who used a diamond in place of the steel point. The diamond scratched the record directly on the gla.s.s. The Hensen-Pipping apparatus has the advantage of taking records directly in the plane of the surface, but it does not make a record which can be reproduced; in case of doubt as to the exact thing represented by the curve, there is no means of referring to the original sounds; and it involves working with a microscope.

[16] Hensen: Hermann's Handbuch d. Physiol., 1879, Bd. I., Th.

II., S. 187.

[Ill.u.s.tration: FIG. 3. Diagrammatic section of recording apparatus.

_a_, diaphragm; _s_, stylus; _g_, guide; _p_, section of plate.]

The apparatus which was used in the following experiments consisted essentially of two recording devices--an ordinary phonograph, and a recorder of the Hensen type writing on a rotary gla.s.s disc (see Fig.

5, Plate X.). Of the phonograph nothing need be said. The Hensen recorder, seen in cross section in Fig. 3, was of the simplest type. A diaphragm box of the sort formerly used in the phonograph was modified for the purpose. The diaphragm was of gla.s.s, thin rubber, or goldbeater's skin. The stylus was attached perpendicularly to the surface of the diaphragm at its center. The stylus consisted of a piece of light bra.s.s wire bent into a right angle; the longer arm was perpendicular to the diaphragm; the shorter arm was tipped with a very fine steel point, which pointed downward and wrote on the disc; the point was inclined a trifle to the disc, in order that it might 'trail,' and write smoothly on the moving disc. The stylus had no fulcrum or joint, but recorded directly the vibrations of the diaphragm. In early experiments, the diaphragm and stylus were used without any other attachment.

But a flexible point writing on smoked gla.s.s is a source of error.

When the disc revolves under the stylus, the flexibility of the diaphragm and of the stylus permit it to be dragged forward slightly by the friction of the moving surface. When the diaphragm is set vibrating the conditions are altered, and the stylus springs back to nearly its original position. The apparent effect is an elongation of the earlier part of the curve written, and a corresponding compression of the last verse written. This error is easily tested by starting the disc, and without vibrating the diaphragm stopping the disc; the stylus is now in its forward position; speak into the apparatus and vibrate the diaphragm, and the stylus will run backward to its original position, giving an effect in the line like _a_ (Fig. 4). If the error is eliminated, the stylus will remain in position throughout, and the trial record will give a sharp line across the track of the stylus as in _b_.

[Ill.u.s.tration: FIG. 4.]

This source of error was avoided by fixing a polished steel rod or 'guide' at right angles to the vertical part of the stylus, just in front of the stylus; the stylus trailed against this rod, and could not spring out of position. The friction of the rod did not modify the record, and the rod gave much greater certainty to the details of the sound curve, by fixing the position of the vibrating point. This rod or guide is shown in Fig. 3 (_g_).

The disc was driven directly from the phonograph by a very simple method. A fine chain was fixed to the shaft carrying the disc, and wrapped around a pulley on the shaft. The chain was unwound by the forward movement of the recording apparatus of the phonograph against the constant tension of a spring. When the phonograph apparatus was brought back to the beginning of a record which had been made, the spring wound up the chain, and the disc revolved back to its original position.

A T from the speaking-tube near the diaphragm box was connected by a rubber tube with the phonograph recorder, so that the voice of the speaker was recorded both on the smoked gla.s.s plate and on the phonograph cylinder. The advantages of such a double record are that the possible error of a transcription process is eliminated, and yet there is an original record to which it is possible to refer, and by which the record measured may be checked.

An important feature in the method was the rate at which the disc revolved. The disc turned so slowly that the vibrations, instead of being spread out as a harmonic curve, were closely crowded together.

This had two great advantages; the measurements were not so laborious, and the intensity changes were much more definitely seen than in the elongated form of record. Each syllable had an intensity form, as a 'box,' 'spindle,' 'double spindle,' 'truncated cone,' 'cone,' etc.

(cf. p. 446).

The disc was run, as a rule, at a rate of about one revolution in two minutes. The rate could be varied to suit the purposes of the experimenter, and it was perfectly possible to procure the usual form of record when desired. As a result of the low rate, the records were exceedingly condensed. The records of the 300 stanzas measured are on two gla.s.s discs of about 25 cm. diameter, and as much more could still be recorded on them.

The diaphragm and the speaking tube were the great sources of error.

For measurements of time values the particular component of the tone to which the diaphragm happens to vibrate is not important, but the record of intensities depends on the fidelity with which the diaphragm responds to a given component, preferably the fundamental, of the tone. The speaking tube has a resonance of its own which can be but partly eliminated. For the records here recorded either gla.s.s or goldbeater's skin was used as a diaphragm. Goldbeater's skin has the advantage of being very sensitive, and it must be used if the subject has not a resonant voice. It has the great disadvantage of being extremely variable. It is very sensitive to moisture, even when kept as loose as possible, and cannot be depended on to give the same results from day to day. The records marked Hu., Ha. and G. were usually taken with a gla.s.s diaphragm, which has the advantage of being invariable. As the phonograph records show, gla.s.s does not modify the lower tones of the male voice to any extent.

[Ill.u.s.tration: PSYCHOLOGICAL REVIEW. MONOGRAPH SUPPLEMENT 17. PLATE X.

Opposite p. 436.

The apparatus is shown arranged for taking parallel records on the smoked gla.s.s disc, and on the cylinder of the graphophone. On the left is shown the microscope with which the records on the gla.s.s disc were measured. ]

The speaking-tube used was of woven material, not of rubber, and a pad of felt was kept in the tube near the diaphragm box. As far as possible more damping was used at the other end of the tube, but this had to depend on the voices of the subjects.

The best check on the performances of a diaphragm is the number per second and character of the vibrations. The pitch may be calculated from the rotation rate of the disc, which is very constant, as it is driven at a low rate by the well-regulated high-speed motor of the phonograph. But it is better to place a fork in position to write on the disc and take a parallel record. All the records were taken with the vowel 'a' (sound as in father). This vowel has a very characteristic signature, which is easily seen, even in a very closely packed curve, and the correctness of this is one of the best guarantees that the fundamental of the tone is actuating the diaphragm (though that does not mean that the diaphragm is actually giving the vibration frequency of that fundamental).

Every record was repeated at least twice, and both records were measured. In many of the experiments the intensities were fixed by the conditions of the experiment. There was always the corroborative testimony of the phonograph diaphragm; for the two were not apt to err together. It was easy to determine if the actual intensity relations were preserved in the phonograph (but it could not be taken for granted). Each record was reproduced on the phonograph immediately after it had been taken, and both subject and operator listened for anomalies. In practice it was not hard to get records of the single vowel used (at a small range of pitch which was never more than a third or fourth and was nearly always much less) which represented fairly well the relative intensities. Beside the checks spoken of above, every record was repeated by a number of subjects, and the comparison of the results of different voices shows uniformity.

The recording of spoken verse is another matter. It is not difficult to test a diaphragm carefully through a small range, but to be certain of its action at all the pitches and qualities of the speaking voice is impossible. A stable diaphragm, gla.s.s or mica, would have to be used, and careful corrections made for the different vowels.

At best, when the records are satisfactory, nothing can be said for the measurements of intensity but that they represent relations of more or less; the diaphragm has a minimum intensity, below which it does not vibrate, and a maximum intensity, above which the amplitude of its vibrations does not materially increase without breaking into partials and 'blasting.'

The disc recorder, which had for a mount a modified microscope stand, was placed on the shoe of the disc stand and clamped. The wax and disc records were adjusted at known starting-points and the stylus carefully lowered, by the rack and pinion adjustment, to the surface of the disc. After a preliminary trial of the diaphragm the apparatus was started, and when at full speed at least two satisfactory records of the material were taken. When the disc had made a single revolution--a record of some ten or fifteen stanzas--the recorder was fed inward to a new circle on the disc. After the records were taken, a microscope with either 2 or 4 Leitz objective and a micrometer ocular was subst.i.tuted for the recorder. The phonograph recorder was raised and drawn back to its starting point, and the disc came back to its original position. The microscope was focussed, and adjusted by the screw of the shoe until it had the record line in its field; the micrometer furnished an object of reference in the field. The phonograph, now carrying the reproducer--if possible without a horn, as the tones are truer--was started. At the first syllable of the record the apparatus was stopped by the device furnished on the 'Commercial' phonograph, and the plate was turned by adjusting the screw at the phonograph carriage, which changed the length of the chain connecting the two records, until the record of the first syllable was at some chosen point in the field. In cases of records of poetry it was found better to have a set of syllables, say 'one, two, three' prefixed to the record, for this adjustment. The phonograph was again started, and the curve-forms representing the spoken syllables filed past the point as the phonograph repeated each syllable. The rate was slow enough, with the objective 2, so that there was no difficulty in observing the pa.s.sing syllables. After the conformity of the phonograph record had been noted by the operator, and the subject had pa.s.sed judgment on the phonograph as saying satisfactorily what he had said, the curve-forms were measured with the micrometer. The record was fed slowly through the field by means of the chain screw on the phonograph carriage; and measurements of the lengths of syllables gave their time values. The micrometer was pa.s.sed back and forth across the form by the shoe screw, for the measurements of amplitude (intensity). The micrometer measurements in this case could be made at least as rapidly as measurements of kymograph curves.

The measurements, with the powers used, are accurate to.01 sec.

The smoked disc records are to be preferred to those scratched with a diamond, because of the superior legibility of the line, an important item if thousands of measurements are to be made. The records are fixed with sh.e.l.lac and preserved, or they may be printed out by a photographic process and the prints preserved. The parallel set of wax records is preserved with them. There are several ways in which the wax records lend themselves to the study of rhythmic questions. It is easy to change the rate, and thereby get new material for judgment, in a puzzling case. Consonant qualities are never strong, and it is easy so to damp the reproducer that only the vowel intensities are heard.

The application in the study of rhyme is obvious.

All the series consisted of regular nonsense syllables. The accented and unaccented elements were represented by the single syllable 'ta'

('a' as in father). Rhymes were of the form 'da,' 'na,' 'ga' and 'ka.'

In other parts of the work (cf. Table IV.) the vowel o had been used in rhymes for contrast; but the same vowel, a, was used in these records, to make the intensity measurements comparable.

The records of the measurements were as complete as possible. The sonant and the interval of each element were measured, and all the pauses except the stanza pause were recorded. The intensity of each syllable was recorded beneath the length of the syllable, and notes were made both from the appearance of the curve and from the phonograph record.

_2. The Normal Form of Unrhymed Verse._

To determine the influence of a subordinate factor in rhythm such as rhyme, it is necessary to know the normal form of verse without this factor. It is natural to a.s.sume that the simplest possible form of material would be individual feet recorded seriatim. But on trial, such material turned out to be very complex; the forms changed gradually, iambs becoming trochees and trochees changing into spondees. It is very probable that the normal foot occurs only in a larger whole, the verse.

To corroborate the conclusions from perceived rhythms as to the existence of variations in earlier and later parts of the verse, a table of mean variations was prepared from the material recorded and measured for other purposes.

TABLE VI.

MEAN VARIATIONS.

Iambic tetrameters; variations of each element from the average foot of the entire stanza.

[Label 1: Unaccented Element of Foot.]

[Label 2: Accented Element of Foot.]

[Label 3: Percentage M.V. of Unac. El.]

[Label 4: Percentage M.V. of Ac. El.]

Hu. 8 stanzas [1] [2] [3] [4]

M.V. 1st foot 0.9688 1.3125 11.1 7.8 2d " 0.8125 0.6563 9.3 3.9 3d " 0.8438 1.1875 9.7 7.1 4th " 0.9688 11.

Av. foot of all stanzas 8.69 16.88

Geo. 10 stanzas, no accents or rhymes within the verse: M.V. 1st foot 2.725 2.775 24.6 13.3 2d " 1.300 1.325 11.8 6.4 3d " 1.400 2.050 12.7 9.8 4th " 2.750 24.9 Av. foot of all stanzas 11.05 20.85

Geo. 8 stanzas, accents and rhymes within the verse: M.V. 1st foot 1.4843 2.4687 13.1 11.5 2d " 1.4219 2.6875 12.6 12.6 3d " 1.7031 2.5312 15.1 11.8 4th " 1.8594 16.4 Av. foot of all stanzas 11.31 21.38

The last element has the 'finality-form' and is not comparable to the other accented elements and therefore is not given.

Dactylic tetrameters (catalectic); variations of each element from the average foot of the entire stanza:

[Label 1: Accented elements of Foot]

[Label 2: 1st Unaccented element of Foot]

[Label 3: 2d Unaccented element of Foot]

[Label 4: Percentage M.V. of Ac. El.]

[Label 5: Percentage M.V. of 1st Unac. El.]

[Label 6: Percentage M.V. of 2d Unac. El.]

[1] [2] [3] [4] [5] [6]

Me., Ha., 8 stanzas, normal: M.V. 1st foot 1.6875 1.2813 1.8125 9.70 9.76 10.5 " 2d " 1.0613 1.0613 1.4061 6.1 8.0 8.1 " 3d " 1.6875 1.3125 1.3750 9.7 9.9 7.9 Av. foot 17.38 13.18 17.31

Geo. 4, stanzas, abnormal type of dactylic foot: M.V. 1st foot 1.5000 1.1250 1.2813 11.5 11.0 8.7 " 2d " 1.5625 1.1250 1.1250 12.0 11.0 7.6 " 3d " 1.3437 1.1873 0.8737 10.3 11.5 5.9 Av. foot 13.00 10.25 14.75