development of p. b. lists in hindi

Development of P. B. Lists in HindiBY

Dr. MOHINDRA,(Lady Hardinge Medical College Hospital, New Delhi).

The value of speech audiometry as an important adjunctto the established methods of testing hearing, is well-recognised,since it provides useful information which is not elicited by anyof the previous tests, thus far known.

During the past few centuries, the methods of testing hearinghave passed through various phases, from spoken and whisperedlive-voice tests, to examination with tuning-forks, to pure-toneaudiometry and speech audiometry.

Though, the ancient Egyptians' often discussed the connec-tion between deafness and ear disease, it was not until the 15thcentury that the earliest tests of hearing, using live-voice werementioned. During the 19th century several tuning-fork testssuch as the Weber 2 test (1829), the Rinne test (1855), the Gelletest (1881), the Schawbach test (1885), the Galtonis Whistle(1893) and tests with the monochord, some of which are in use,even today, were described. These tuning-fork tests made animportant land-mark in the history of hearing tests.

It was towards the end of the 19th century that Bezold, 2

introduced the idea of quantitative measurement of deafness, thehearing tests till then, being purely qualitative in nature. Hecompared the length of time, in seconds, during which a tuning-fork could be heard by the patient, with that of a normallyhearing person.

With the advent of pure-tone audimeters during the earlypart of the present century (1921 Guttman,' 1922 Fowler andWegel), audimetry entered a new era of precision. It providedan accurate, rapid, and reliable method of testing hearing forpure-tones. Though, it was an important step forwards in theprecise measurements of degree of deafness, it was not too easy,

Development of P. B. Lists in Hindi 79

according to Davis, to translate this information into how exactlya deaf person would hear the speech of his fellow-beings ineveryday life, which is all-important to him. He is not interestedin hearing pure-tones, perse. The only information regardinghearing for speech which a pure-tone audiogram could yield,was by means of conversion formulae and calculations, whichcan never be very accurate.

Speech-audiometry, by using the various articulation tests,fills this important gap in the information regarding the deafperson's ability to hear speech, by using, speech itself, as a testmaterial. These tests are now as accurate and reliable as testswith the pure-tone audiometers.

So far, speech audiometry is conspicuous by its absence inour country, mostly, because of the non-availability of the testmaterials, based on scientific lines, in our own languages. Thepresent study has been carried out, with this objective in mind,and an attempt has been made to develop test-materials inHindi, the national language of India. Since a fairly accurateidea of the speech threshold-level or the hearing loss for speech,can be obtained from the pure-tone audiogram, it was thoughtnecessary to construct only the lists of Phonetically - balancedmonosyllable Hindi words, which would be valuable for measu-ring discrimination Iosses. No attempt has, therefore, been madeto assemble lists of Spondaic words which are used commonlyfor purposes of threshold measurements, in the English language.

PROCEDURE

The first important step in the construction of these listswas the selection of basic Hindi vocabulary which could be usedas a pool for the monosyllable words. Since no analytical studyof the language was available, a simple manual in Hindi,written in. an attempt to teach the spoken language, in itssimplest from, to the foreigners, was used for this purpose. Itsbasic vocabulary consisting of 1573 words, was analyzed intovowels and consonants, and the relative frequency of eachspeech sound was then calculated in terms of their percentage

80 Mohindra

values. As a cross-check, 3 paragraphs of spoken Hindustaniselected at random, were also similarly analyzed and the resultstaken into consideration.

Next, the distribution of the individual vowels andconsonants within each list of 50 words was planned, by dividingtheir percentage values into a quota, which was adjusted intothe initial, final and middle positions of the selected words. Togive each list an accurate representation of the language as such,few compound words were also included, their number beingconstant in each list.

While selecting the individual words, the following criteriasuggested by Egan-et-al were kept in mind,

1. Monosyllable words of consonant - vowel - consonantpattern. (C.V.C.)

2. Words of everyday use.

3. Words of equal difficulty.

4. Phonetically balanced lists to provide a normal samplingof everday speech,

5. No repetition of words in the same list. 200 monosyllablewords were initially selected from the basic pool. Of these 100words were judged to be the most commonly spoken and ofequal difficulty, taking into consideration the vocabulary limitsof the listeners, many of them being illiterate.

Two lists of 50 words each, were constructed out of the 100finally selected words. The number and distribution of theconsonants and vowels assigned to each list was then adjustedinto simple words, of every day use keeping the initial consonantand vowel strictly in view. The frequency of the final consonantcould not be satisfactorily controlled because of the difficulty ofobtaining commonly - spoken words within the preimposedlimitations, though a definite attempt was made in thisdirection, and many of the final consonants were finallyadjusted fairly close to the values required.


Three persons individually rated the final lists regardingwords of equal difficulty. Any words thought too easy or toodifficult or found unsuitable otherwise by more than one exami-ner, were eliminated. Three scrambling of each of the twomaster lists (each of 50 monosyllable words) were obtained, theorder of the words in all the scrambled lists, being at random.Thus a total of 5 phonetically balanced lists were obtained.

RECORDING OF LISTS

All six lists were recorded on magnetic tape (7.5"/sec. usingAmpex model 401A Tape recorder) by the same speaker, whowas instructed as follows :-

- To keep the intensity of his voice fairly constant by practi-sing with a • 1 V U ,, meter beforehand.

- To speak a "carrier- word " before each "test- word ",in order to help modulate his voice as well as serve as a signalto the subject to anticipate the test-word.

- To speak the "test-word" as it would naturally follow the"carrier - word " (without making a break between the twowords).

Before recording each list, few simple instructions to be givento the patient, regarding what to expect and how to co-operateand finally a 11 get ready signal " were also recorded. An intervalof 10 sec. was allowed between the instructions and the firstcarrier-word, followed immediately by the test-word. There-after, 5 sec. were allowed between the two consecutive carrier-words and this interval was kept constant throughout each list.

A 1000 cycles calibration tone was recorded as a referencelevel.

STANDARDIZATION

To check up if all the lists consisted of words of equeldifficulty, trials were made on 6 normally hearing individualswithin the age-group of 18-38 years, each with a normal pure-tone audiogram, they formed a group of untrained listeners, and

82 Mohindra

were instructed-beforehand as to the nature of the experimentand what was expected of them.

Initially, each individual was presented with all the 6 listsin the same order, at 60 db. S. P. L., monaurally, throughstandard playback equipment. At the same sitting, all the 6lists were presented at the following intensity levels as well

15 db; 20 db; 25 db; and 30 db; & 35 db; (40 db. for 2Subjects only) only I Subject (No. 2) could not be presented withall the lists at 15 db. The lists and levels were, however,randomised for each listener according to a random latin-squaredesign. No list was repeated. The following data were obtained,for each Subject at the same sitting, to minimize the factors offatigue and memory :—

1. The number of words repeated correctly i.e. the articula-tion score.

2. The number of errors per word for each listener.

Any word missed out once or less by all individuals wasrated as too easy and any word missed out by most or all of themwas rated as too difficult. Words of both categories were elimi-nated.

Articulation curves (figs. II-VII)- were constructed with theabove data, for each subject, by plotting the articulation scorealong the ordinate and the intensity levels in db. along theabsissa. Such curves were also constructed for the averagesubject as well as for average subject and average lists (fig. VIII& IX).

The mean deviation values have been calculated for eachlist at all the Sound pressure levels used in the experiment.These are shown in chart I.

RESULTS

It may be seen that the average articulation curve obtainedin the present study compares fairly well with the established

Development of P. B Lists in Hindi ‚93

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'30-11/

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1--- I I 1 1 I I -10 15 20 2 O 35 40

Sound Pressure Level in fl8

Fig. II

No. of list. 15 db. 20 db. 25 db. 1 30 db. 3 db. 40 db,

1 22 36 88 i 88 94 98

2 i 54 68 88 96 58 98

3 1 36 1 76 88 i 84 94 98

4 40 76 82 86 90 90

5 42 54 78 88 88 96

6 12 40 72 84 96 98

84 Mohindra

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90

80

70

60

50C

C 40

30

20

10

05 10 15 20 25 30 35

Sound Pressure Level in DB

Fig. III

No. of list. 15 db. 20 db. 25 db. ( 30 db. 35 db. 40 db.

1 26 42 64 86 96

2 16 48 86 88 96

3 I 8 58 62 90 984 fff

i 16 46 52 76 88

5 10 38 56 96 90

6 14 48 70 92 I 92


loo

90

80

ó 70

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5db 10db 15äb 20db 25dó 34b 35db

Sound Pressirre Level in D3

Fig., IV

•No. of list. 15 db_ 20 db. 25 db. ( 30 db. 35 db. I I 40 db.

1 8 56 84 86 92

2 36 64 70 66 92

3 22 48 78 88 86

4 36 62 84 88 96

5 34 66 82 90 82

6 l 44 62 84 90 94

6

o 70

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40

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90

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5 to t5 20 25 0 35

86 Mohindra.


Fig. V

No. of list. 15 db: 20 db: 25 db. 30 db. 35 db.

1 6 —,--- 24 60 82 90

2 4 26 66 88 90

9 ^ 0 20 78 88 94

4 0 34 1 68 76 88

5 6 34 58 78 84

6 I 4 20 66 76 82

No. of list. 15 db. 20 db. 25 db.

1 16 62 76

2 18 64 82

3 12 60 80

4 14 62 Í 90

5 0 82 96

6 0 i 58 86

30 db. 1 35 db.

88

98

88

94

88

90

86

86

90

96

92

96

Development o f P. B. Lists in Hindi

87

100

90

80

ate° 70

E 60

soa0

40

30

20

10

0 5 tO i5 20 25 30 35

Sound Pressure Level in DI3

Fig. VI

88

Mohindra

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80-1

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0 60

50

• 40

30

20

10

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e __aj , ._ ;,7/rf

I y^ %

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5 10 15 2O 25 30 35 40


Fig. VII

No. of list. 20 db. ( 25 db. 30 db. 35 db. 40 db.

0 54 58 92 90

16 72 82 86 92

8 50 72 76 78

4 6 48 70 74 82

5 14 38 64 84 86

6 22 42 72 84 90


‚Co

90

80

70

W

Q 60v

Z 50O

40

V30

20

10

0

5 to 15 20 25 30 35 40

Sound Pressure Level in DBArticulation Curves for Average Subject

Fig. VIII

90 Mohindra

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90

80

70w

0a

vs60

z_O 50

40u

I-á 34

d20

4

10

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5 10 15 20 25 30 35 40

Intensity Level in DBArticulation Curve for average subject and average list

Fig. IX

Mean Deviation Chart I

Intensity Levels in DB.

Lists 15 20 25 30 35

I x 13.0 40.0 71.0 81.3 93.69.1 22.5 12-5 9.8 2.6

II x 21.3 47.6 77.3 86.3 92.618.6 20.1 8.3 18.3 4.0

III x 13.0 45.0 74.3 86.6 89'6_ 16.1 33.6 6.3 8.6 7.1

IV x 17.6 47.6 70.6 80-3 871015.5 22.8 16.0 6.6 5.6

V x 15.3 48-0 68.0 84-3 87.313.1 22.1 19.3 10.6 4.6

VI x 12.3 41.6 70.0 84.3 90.615.1 29.3 15.0 7.8. 5.6

Total x 15-4 44.5 73.5 83.8 90.1

Development of P. B Lists in Hindi 91

normal articulation Curve using speech materials in Englishand eight other languages in which the speech audiometrymaterial has so far been developed.

DISCUSSION

According to Davis' (1948), what a deaf person wants tohear most is the speech of his fellow human-beings, auditorycommunication being one of the basic needs of the mankind.The traditional methods of testing hearing by live-voice werefound to be unreliable since their very inception, on account ofthe inability to control the intensity of the speaker's voice ondifferent occasions, and quite often even at the same sitting.Besides the other disadvantages, such as the distortion of speechsounds at very loud or very soft levels, comparison of the resultsof different testers, is impossible. Inspite of the preciseness ofthe pure-tone audiometry, an accurate measure of the hearingloss for speech cannot be obtained.

Having realized the unreliability of the live-voice tests,Bryant in 1904, made the first attempts towards direct measure-ments of the hearing loss for speech, by using lists of selectedmonosyllables recorded on a phonograph. Later, Fletcher' in1926, described the first widely - used speech test, by employingrecorded spoken digits as test - items. Since digits could be easilyrecognized by their vowel content alone, they were found un-suitable for testing high-tone hearing losses..

The foundations" of the modern speech-audiometry werehowever, laid by the work carried out at the Bell-telephone labo

-ratories, since 1920, by Fletcher-' - Steinberg and associates, inan attempt to devise methods of assessing the efficiency of thetelephone systems to transmit speech. They developed lists ofmonosyllable words on Consonant-Vowel-Consonant pattern,grouped at random, and were the first to use these lists as testingmaterial in 1929.

The notion of phonetically - balanced word-lists as a repre-sentative sample of everyday conversation speech, originated

92 Mohindra

from the extensive work carried out during the Word War II,for testing communication equipment. The first standardizedspeech tests emerged out of the work carried out at the Psycho-acoustic laboratory of the Hai yard University by Egan-et-al b in1947.

Two aspects of hearing may be investigated by means ofthe tests employed in speech audiometry, the hearing for Speechat threshold and supra-threshold levels. According to Carhart 9

1946, Fletcher 10 1950, Hirsh-et-al" 1952 and Palva 12 1952, thethreshold levels for speech or the hearing loss for speech can befairly accurately predicted from a pure-tone audiorgram, by cal-culating the average values of the three Speech frequencies, itis the hearing at Supra-threshold levels however, which yield sinformation of great diagnostic and prognostic value, notobtained by any of the previously existing method.

According to Silverman 1950, as Speech becomes louder,more words are heard and repeated correctly by the normallistener. This is best illustrated by means of an articulationcurve, charted by plotting the % age articulation - score i.e. thenumber of correctly repeated words, along the ordinate and theintensity levels, along the absissa. A list of 50 PB words is pres-ented to the subject at various sound pressure levels, 10 db•apart, to complete the curve. The maximum score is usuallyreached within the range of 30-40 db. The normal articulationcurve (Fig. X) is "S" shaped. Changes in shape occur indifferent types of deafness as may be seen in Fig. XI. In cases ofpure conductive deafness, if speech is made loud enough, thearticulation score does reach the normal value of 100% and thearticulation curve is normal in shape, though it is displaced asa whole to the right, the amount of displacement depending onthe degree of hearing loss. In cases of pure perceptive deafness,on the other hand, the curve rises with the intensity of speechupto a certain limit, beyond which, any further increase inintensity does not increase the articulation score and the curveflattens out. In some cases however, it may exhibit a downwardtendency indicating that speech, louder than a certain limit,

development of p. b. lists in hindi

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