The Fatigue of Deafness

UNDER normal conditions, in a wellbalanced and duly coördinated human machine, the usual, and multiform, processes of daily life are conducted under the control of an habitually sub-conscious directorate which duly apportions the adequate expenditure of motive power, of nervous energy; when the balance is impaired, or the coördination becomes imperfect, an additional sum of energy is required, for purposes of substitution, or of compensation.

So long as the extent of the requirement falls within the limit of the amount at sub-conscious disposal, the substitution may be made by the increase of some forms of expenditure at the expense of others less immediately important, or by the limitation of all and the creation of a contingent reserve. Beyond the limit thus provided for the unusual expenditure of energy, expenditure can be made only under direction of the will, as a conscious effort; though this, if long continued as a deliberate demand met by a contribution from the reserve, may become a habit, a procedure wholly or partly under conscious direction, but none the less a draft upon the daily income of vital force beyond that for which economic provision had originally been made, and one which is surely, remonstrantly, to be recorded under some form of expression of the physical conscience.

The illustrations of this balanceadjustment of accounts where it concerns the functions of organic life, those complicated laboratory processes by means of which we live and move and have our physical being, are less apt to fix our attention than those which concern the peripheral, the intraand trans-mural activities of our city of residence.

The experience of an ill-fitting shoe, of a maimed digit, brings at once to our consciousness the necessity for substitution and for compensation, together with the recognition of an unusual expenditure of nervous energy; while the temporary lessening of tactile sense in the finger-tips on a cold morning in the country may be a wholesome lesson in gratitude for the bounties we possess but learn to disregard because they grow familiar to our daily use. The lame, the halt, and the blind appeal without words to our sympathy and to our appreciation of their sorry case, and we readily accord them such helpful expenditure of energy, on our part, as shall supplement their own compensatory effort, but there are other less evident disabilities quite as needy when once their wants come to be understood.

Among these is the impairment of function of a sense-organ so completely developed at birth as to make it immediately operable as a channel for the reception and transmission to the brain of external stimuli, and of such range, both in limit and in acuteness of perception, as to make its sense-provision a striking example of the bounty of nature.

That impairment of the hearing power should be an inconvenience is readily understandable; that it may make so large a demand upon the nervous energy as to be a source of fatigue, needs personal experience, or observation, for its full appreciation.

Changes of tension in the normal sound-transmitting apparatus of the middle ear, or other interferences with the passage to the perceptive apparatus of sound-waves in their accustomed form and volume, as a result of disease, may so alter or decrease the sounds perceived as to make them unfamiliar and needing explanation by a mental process; and the total, or even partial, abolition of the hearing power of one ear, the other remaining intact, may so far interfere with the ability to appreciate the direction of a soundsource, which is one of the habits of normal binaural audition, as to be not only a cause of embarrassment, but to constitute a serious demand upon the nervous energy as well.

To the individual possessed of a reasonably perfect bodily machine, the working limitations incident to possible imperfections in that machine are with difficulty appreciable by any figurative construction, and it is therefore only by the sufferers themselves, or those whose business it is to study imperfections, effect repairs, and suggest compensations, that the full cost, in expenditure of nervous energy, required to overcome an obstacle to perception, can be adequately understood.

With the abolition, or limitation, of receptivity through one or another of the channels of communication by means of which the human machine is kept in touch with its environment, a portion of the nervous energy constantly seeking peripheral expression must be expended in the adjustment to the new condition and the utilization, in a compensatory way, of other channels of communication.

Given, therefore, a limitation of sight, of hearing, or of tactile sense, an expenditure of energy, in what may be termed conversion of force, is required, evidencing itself in the individual as that complex of symptoms to which we give the name of fatigue; and the purpose of this communication is to direct attention to that type of the mechanism of force-conversion which is evidenced by what may be called the fatigue of deafness.

In view of the fact that the normal ear has very nearly double the amount of hearing power necessary for the ordinary uses of every-day life, it is comprehensible that one half of the binaural power may be lost without serious inconvenience to the individual; beyond that point of defect, however, a distinctly appreciable effort must be made to hear, and, in default of this, a still further effort to gather, through other sensory channels, such information as may serve to supplement the defective hearing.

The channel especially available for this supplementary purpose is that of sight, because through it there may be brought to knowledge the character of the particular mechanical process originating the mode of motion to our appreciation of which we give the name of sound; and the most important illustration of this visual aid to defective hearing is found in the effort to appreciate the sounds of the voice at their true formative value. While the vowel sounds are the threads upon which the parts of speech are strung, the consonant sounds are checks or alterations of tone, of differing form and force; and those which nearly resemble each other, in both force and musical value, are produced by the coördinating operation of very nearly the same sets of muscles, and hence are accompanied by very nearly the same facial expression.

Given, therefore, an average case of marked impairment of hearing, the result of a slowly progressive middleear disease, for instance, the patient will hear most readily the consonant sounds which require most muscular force in their production, including the four explodents, — t, d, p, b, — very nearly resembling each other in force and tone-value, and all formed in the front of the mouth, p and b being distinctly labial, and t and d as distinctly due to the contact of the tip of the tongue with the upper incisors. In the event of a thickening of the drumhead, or other lessening of the mobility of the sound-transmitting apparatus of the middle ear, an obstacle is presented to the passage of sound-waves inward; excluding especially such short sound-waves of moderate intensity as those constituting the upper partials of the consonant checks.

Much as these four explodents differ in projectile and in pneumatic value, the differences in the pitch, and in the relative disposition, of their qualitative over-tones is slight; a moderate degree of obstruction serves to level the differences, and these consonants, which are markedly distinctive in meaning, sound very much alike.

This was interestingly illustrated in the early telephone experiments, when a thick iron plate was used as the sound-receiving armature of the magneto-transmitter, instead of the thin ferro-type disk which came later into use. The thick iron plate, by its comparative immobility, presented so great an obstacle to the moderate impulse of the short sound-waves of the qualitative over-tones, as to make each t, p, b, and d, in a spoken sentence sound only as a dull thud to the listening ear.

From the position and formation of these consonants, and the necessity for distinguishing accurately between them, it usually ensues that their differentiation makes the first step in that instinctive study of lip-reading which, to the appreciably deaf person, becomes eventually more or less habitual, and offers another channel for the expenditure of nervous energy, in the effort to see, as well as to hear, the spoken word.

The other consonant sounds having the greatest logographic, or forcevalue, k and g, for example, are formed in the back of the mouth, and are accompanied by a lesser degree of recognizable facial expression than the front consonants, while the consonants having the least force-value, f, l, m, n, very nearly resemble, in the mechanism of their construction, the harder consonant sounds of nearly the same musical value.

It thus comes about that the deaf person will, when a soft consonant occurs in a sentence, substitute for it, mentally, the hard consonant sound most nearly resembling it, the consonant which would probably have been heard had it been used. In any given sentence, therefore, there are, to the very deaf, though seeing, persons, certain consonant sounds which are distinctly heard, others which are imperfectly heard, others which are detected by sight, and still others which are merely inferred.

In the higher grades of imperfection of hearing, therefore, both the effort to hear and the effort to see, combined, are inadequate to the presentation to the mind of the complete spoken sentence, since there remain gaps in the array of consonant sounds which must be filled in from the context; the completion of the sentence thus presented meaning the solution of a puzzle, and being therefore a third demand upon the nervous energy, in addition to those required through the medium of hearing and of sight.

In other words, the exercise of the ordinary communication with his fellow men demands of the person of imperfect hearing the operation of three distinct brain-processes to achieve that which is normally accomplished without conscious effort; and the resultant fatigue may be justly estimated as a possibly important factor in many cases of nervous over-strain.

But there are still other demands in the way of compensatory expenditure of nervous energy which make even a very little impairment of hearing a serious handicap in the race of life, among these being the difficulty in determination not only of the direction of a sound-source, but of the qualitative value of the sound as well, and a distortion of the central sound-picture resulting from imperfection in hearing in one ear, the other ear being normal in function.

Since the head casts a sound-shadow, as it does a light-shadow, if one ear hears normally and the other ear but one half as much, there will be a marked difference in the sound-perception of a spoken sentence, according to the direction from which the sound proceeds; or, if there be, in the imperfect ear, an alteration of tension of its sound-transmitting apparatus, with corresponding accentuation of certain tones, the central adjustment of the distorted to the normal sound-picture requires a constant expenditure of energy to keep the concept true.

Still another demand upon the strength and endurance of the person with imperfect hearing is incident to the fact that an obstruction which hinders the passage of sound in one direction will equally hinder its passage in the opposite direction. If the cause of the deafness be an obstruction to the passage of sound through the middle ear from without inward, this obstruction will interfere with the normal passage outward of those sounds consequent upon the activity of the human machine: sounds made by the contraction of muscles, sounds incident to the movement of joints, and, more especially, the friction sounds made by the blood flowing through the bloodvessels, large and small, tones of low pitch for the former, and of high pitch for the latter.

Whether constant or intermittent, monotonous or variable, these circulation sounds have to be reckoned with in the adjustment of the compounded tone-picture to the uses of the day; and in their turn make a demand on the energy, expressed in judgment and self-control, of one who would keep the even tenor of his way.

Of all the external sounds which the human ear is capable of receiving and translating, that of the human voice is the most pregnant with meaning, and often the most difficult to interpret; and when that which, to the hard-of-hearing, is a distorted sentence is still further disfigured by imperfect or uneven utterance, the burden imposed by misfortune is made still more heavy by the carelessness of those who might help to lift it.

To the person, who, through imperfect hearing, has distinctly limited relationship with his fellow men, to the aged and the otherwise infirm, in whom the progressive contraction of the accommodative muscles within the drumhead has, by limiting the movement of the sound-transmitting apparatus, decreased the transmission of short sound-waves, and therefore the ability to hear truly the qualitative over-tones distinguishing the consonant sounds, there are two classes of speakers to be regarded with dread: those who articulate imperfectly, who may be said to be slovenly in speech; and those uneven speakers who, in a single sentence, rise to the fullness of their vocal capacity, and then sink to a whisper. The slovenly speaker demands of his hearer an acute attention and liberal translation, while the effort to follow the billowy lecturer may be compared to that of a lame man who is trying to keep his footing in a rocking boat.

One of the most effective helps which we can render those fellow travelers who find the fatigue of their deafness a daily load, is gentle speech, wellchosen, well-modulated, of an even tenor and, above all, articulate. When it is necessary to increase the voice volume, this should be done with due regard to the evenness of tone and the distinctness of articulation; to those who can receive only that which is ministeringly brought to them, to whom the once-accustomed volume of the sound of life has become pitiably diminished, let us bring in gentle mien, carefully, patiently, the best that we have to offer.

The majority of the human handicaps are more evident, and better understood, than is the impairment of hearing, which, without outward sign of disability, may first become of public knowledge as an obstacle to the conduct of the ordinary affairs of life and therefore as something to be contemned; a condemnation reflected often upon its unfortunate possessor, who finds himself thrust aside because he is apparently too slow to comprehend, or because the obstacle to be overcome in getting into touch with him, demands too great an effort in its surmounting.

Daily experiences of this sort, coupled often with the disappointment in the effort to live usefully and selfsustainingly, bring about a sense of isolation and of imprisonment, adding much to the fatigue and incident depression of the pitiably deaf; and while there are no apparent wounds to bind, there are gashes in the spirit and inroads upon the strength of our fellows who hear imperfectly, which make it incumbent upon us to halt a little in the hurry of the highway and give aid.