OF THE SENSE OF HEARING.
As the sense of hearing, as well as that of seeing, gives us
perceptions of remote objects, so it is subject to similar errors, and
may deceive us, when we cannot rectify by the touch, the ideas which
it excites. It communicates no distinct intelligence of the distance
from whence a sounding body is heard: a great noise far off, and a
small one near, produce the same sensation, and, unless we receive aid
from some other sense, we can never distinctly tell whether the sound
be a great or a small one. It is not till we have, by experience,
become acquainted with any particular sound that we can judge of the
distance from whence we hear it; but if, for example, we hear the sound
of a bell, we are at no great loss to determine its distance, any more
than we are of that of a cannon from the report, judging in both cases
from similar sounds, which we have been previously acquainted with.
Every body that strikes against another produces a sound which is
simple in bodies non-elastic, but is often repeated in such as are
elastic. If we strike a bell, a single blow produces a sound, which
is repeated while the sonorous body continues to vibrate. These
undulations succeed each other so fast, that the ear supposes them one
continued sound; whereas, in reality, they form many. A circumstance
of this kind happened to myself, for lying on the bed half asleep,
I distinctly counted five strokes of the hammer upon the bell of the
clock, and rising immediately found it was but the hour of one, and
was convinced by examining the machinery that it had struck no more. A
person, therefore, who should for the first time, hear the toll of a
bell, would very probably be able to distinguish these breaks of sound;
and, in fact, we can readily ourselves perceive remission in sounds.
Sounding bodies are of two kinds; those unelastic ones, which being
struck, return but a single sound; and those more elastic returning a
succession of sounds, which uniting together form a tone. This tone may
be considered as a number of sounds produced one after the other by
the same body, as we find in a bell, which continues to sound for some
time after it is struck. A continuing tone may be also produced from
a non-elastic body, by repeating the blow quick and often, as when we
beat a drum, or draw a bow along the string of a fiddle.
Considering the subject in this light, we shall find the number of
blows or quickness of repetition will have no effect in altering the
tone, but only make it more even or more distinct, whereas if we
increase the force of the blow by striking the body with double the
weight, this will produce a tone twice as loud as the former. From
hence we may infer, that all bodies give a louder and graver tone, not
in proportion to the number of times they are struck, but to the force
that strikes them. And if this be so, those philosophers who make the
tone of a sonorous body, a bell, or the string of an harpsichord, for
instance, to depend upon the number only of its vibrations, and not
the force, have mistaken what is only an effect for a cause. A bell,
or an elastic string, can only be considered as a drum beaten; and the
frequency of the blows can make no alteration whatsoever in the tone.
The largest bells, and the longest and thickest strings, have the most
forcible vibrations; and, therefore, their tones will be more loud and
more grave in proportion to the size and weight of the body with which
they are struck.
If we strike a body incapable of vibration with a double force, or a
double mass of matter, it will produce a sound doubly grave. Music has
been said, by the ancients, to have been first invented from the blows
of different hammers on an anvil. Suppose then we strike an anvil with
a hammer of one pound weight, and then with a hammer of two pounds,
it is plain that the latter will produce a sound twice as grave as
the former. But if we strike with a two pound hammer, and then with a
three pound, the last will produce a sound only one third more grave
than the former. If we strike with a three, and then with a four, it
will likewise follow that the latter will be a quarter part more grave
than the former. Now, in the comparing between all those sounds, it
is obvious that the difference between one and two is more easily
perceived than between two and three, three and four, or any numbers
succeeding in the same proportion. The succession of sounds will be,
therefore, pleasing in proportion to the ease with which they may be
distinguished. That sound which is double the former, or in other
words, the octave to the preceding tone, will be the most pleasing
harmony. The next to that, which is as two to three, will be most
agreeable. And thus universally, those sounds whose differences may be
most easily compared are the most agreeable.
It is most certain that the cause of pleasure in all our senses
originates from the justness of proportion, and that disproportion
never creates a pleasing sensation. The lad whom Mr. Chesselden
restored to sights was at first most delighted with those objects which
were regular and smooth on the surface; from this it is plain that the
ideas we entertain of beauty from the eye originates from regularity
and proportion; it is the same with the sense of feeling, smooth,
round, and uniform bodies are more pleasing than those which are rough
and irregular; why should not therefore the same preference be given by
the ear to the proportion of sounds?
Sound has, in common with light, the property of being extensively
diffused; and also admits of reflection. The laws of this reflection,
it is true, are less understood: all we know is, that sound is
reflected by hard bodies, and that their being hollow, sometimes
increases the reverberation. A wall or a mountain sometimes reflects
sounds so distinct that we are almost induced to suppose it proceeds
from them rather than from an opposite quarter. Vaults and hollow rocks
also produce distinct echoes.
The internal part of the ear is particularly formed for reflecting
sounds, and may, in some measure, be compared to the cavern of a rock.
In this cavity sounds are repeated, and by that means conveyed to the
membranous part of the lamina, which being an expansion of the auditory
nerves transmits them to the mind. The internal cavity of the ear,
which is fashioned out in the temporal bone, like a cavern cut into a
rock, seems to be fitted for the purposes of echoing sound with the
greatest precision.
One of the most common complaints in old age is deafness, which
probably proceeds from the rigidity of the nerves in the labyrinth of
the ear, augmenting as we advance in years, and when the membranous
part of the lamina becomes ossified deafness is the consequence, and
is in that case incurable. It sometimes happens from a stoppage of the
wax, but it may then be relieved by art. In order to know whether the
defect be an internal or art external one, let the deaf person put a
repeating watch into his mouth, and if he hears it strike, he may be
assured that his disorder proceeds from an external cause, and may be,
in some measure, relieved.
It often happens, that people with bad voices, and unmusical ears,
hear better with one ear than the other, and suspecting there might be
some analogy between the ears and eyes, as those who squint have more
strength in one eye than the other, I made several experiments, and
always found their defect in judging properly of sounds proceeded from
the inequality of their ears, and their receiving by both at the same
time unequal sensations, and those persons who hear false also sing
false, without knowing it. They also frequently deceive themselves with
regard to the side from whence the sound comes, generally supposing
the noise to come on the part of the best ear. This, however, is only
applicable to those who are born with a defect in the hearing.
Such as are hard of hearing reap the same advantage from the trumpet
made for this purpose that short-sighted persons do from concave
glasses. As the sight is affected with age so is the hearing, and
equally requires the assistance of art. Trumpets for assisting hearing
might be easily enlarged, so as to increase sounds, in the same manner
that the telescope does bodies; but they could be used to advantage
only in places of solitude and stillness, as the neighbouring sounds
would mix with the more distant ones, and the whole would produce in
the ear nothing but tumult and confusion.
Hearing is a much more necessary sense to man than to any other
animal. In the latter it is only a warning against danger, or an
encouragement to mutual assistance. In man, it is the source of most
of his pleasures, and without it the rest of his senses would be of
little benefit. A man born deaf must necessarily be dumb, and his whole
sphere of knowledge must be bounded by sensual objects. We shall here
notice a singular instance of a young man, who, born deaf, at the age
of 24 suddenly acquired the faculty of hearing. The account, which is
given in the Memoirs of the Academy of Sciences, 1703, page 18, is in
substance as follows:
"A young man, of the town of Chartres, aged about 24, the son of a
tradesman, who had been deaf and dumb from his birth, began to speak
of a sudden, to the utter astonishment of the whole town. He gave his
friends to understand, that for three or four months before, he had
heard the sound of the bells, and was greatly surprised at this new and
unknown sensation. After some time a kind of water issued from his left
ear, and he then heard perfectly well with both. During these three
months he listened attentively to all he heard, and accustomed himself
to speak softly the words pronounced by others. He laboured hard in
perfecting himself in the pronunciation, and in the ideas attached to
every sound. At length, supposing himself qualified to break silence,
he declared that he could speak, though as yet but imperfectly. Soon
after some able divines questioned him concerning his ideas of his past
state, and principally with respect to God, his soul, the moral beauty
of virtue and deformity of vice. Of these, however, he did not appear
to have the slightest conception. He had gone to mass indeed with his
parents, had learned to sign himself with the cross, to kneel down,
and to assume all the external signs of devotion; but he did all this
without comprehending the intention or the cause. He had no idea even
of death, but led a life of pure animal instinct, and though entirely
taken up with sensual objects, and such as were present, he yet did
not seem to have made any reflections upon them. The young man was
not, however, in want of understanding, but the understanding of a man
deprived of all intercourse with society is so very confined, that the
mind is, in some measure, totally under the control of its immediate
sensations."
It is possible, nevertheless, to communicate ideas to deaf men, and
even to give them precise notions of general subjects, by means of
signs, and by writing. A person born deaf, may be taught to read, to
write, and even by the motion of the lips to understand what is said
to him; a plain proof how much the senses resemble, and may supply the
defects of each other.
On this subject it may not be improper to quote a fact, of which I was
myself a witness. One M. Pereire, a native of Portugal, who had made it
his particular study to teach persons born deaf and dumb, brought to my
house a young man who was thus unhappily circumstanced. He was at the
age of nineteen, in the month of July, 1746, when M. Pereire undertook
to teach him to speak and read. More than four months had not elapsed,
when he was capable of pronouncing syllables and words; and in the
space of ten months, he perfectly understood, and could, with tolerable
distinctness, pronounce about thirteen hundred different words. This
education, so favourably begun, was interrupted for nine months by the
absence of the master; who then found him far less intelligent than he
had left him. His pronunciation was vitiated, and of the words he had
learned most of, he retained not the smallest remembrance. M. Pereire
accordingly renewed his instructions in the month of February, 1748;
and from that time he never left him till June 1749. At one of the
meetings of the French Academy this young man was brought them, and had
several questions proposed to him in writing. To these his answers,
whether written or verbal, were highly satisfactory. His pronunciation,
indeed, was slow, and the sound of his voice was harsh; but at these
defects there is little cause to wonder, as it is by imitation alone
that our organs are enabled to form precise, soft, and well-articulated
sounds, and, as this young man was deaf, he could not be expected to
imitate what he did not hear; but which harshness, by the assiduity
and skill of his master, might, however, in some degree, be corrected
afterwards.
In the above case, the expedition of the master, and the progress of
the pupil, who indeed seemed to be no wise deficient in point of
natural ability and understanding, are an ample proof, that persons
born deaf and dumb may, by art, be brought to converse with other men;
and I am persuaded that, had this young man been instructed so early as
at the age of seven or eight, he would have attained as great a number
of ideas as mankind possess in general.