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it have been anticipated that this science would have been brought to such a height of perfection, and that many educated and able men
a would devote themselves solely to one department of it?
Much has been effected in the economy of heat, but it is applicable in such a variety of ways, and to so many purposes, that although much of utility is known, probably still more remains to be understood.
Difficulties in copying an erection consistently with Acoustic Principles.—The most subtle and abstruse phenomenon in the whole range of physical science is sound, which has hitherto been an ignis futuus. In the very limited space of a common apartment, individuals are seen opening their mouths, stretching their necks, and putting the hand to the ear in order to catch that which is not, a false sound being to the ear what occular deception is to the eye. All men fancy it to be within their reach—of this various instances are at present exhibited; and these remind us of a circunstance, related by several authorities, of some Jesuits who erected a building in imitation of one near Milan, where the sound of a pistol shot is repeated upwards of forty times, but although the copy was in appearance the same as the original, yet it was without an echo.
Desertion of Principles in copying Canon Mills, Edinburgh.— Canon Mills, (a place intended for the preparation of gas,) where the first General Assembly of the Free church of Scotland met, is now considered a model for the economy of speech; and several places of worship have been erected as true acoustic copies of this edifice, which consists of, in part, an earthen floor, walls of rough, solid masonry, and slates as they came from the quarry, affixed to wood as it left the saw, all being single, compact materials, with rugged exteriors, having little vibratory action, or sound, the solidity of the bodies, and roughness of the surfaces, being the principles that are favorable to articulation by producing limited undulations ; but the rough surfaces occasion harsh sound on the ear, in the ratio of their proximity to it.
In the copies from the original, instead of being partly earth, the flor is all boarded, and hollow under, giving out much extraneous sound from the action of the feet, and other causes. The walls, instead of being solid and rough, are lined with lath and plaster, hollow between, and smooth on the exterior, consequently having comparatively much more action and sound than the original; while the roof is lined with lath and plaster, in like manner as the walls; not anything being retained in the copies consistent with the properties of Canon Mills, except the general form, which is bad. All this deviation from the original seems strange, when it is considered that not a single atom in a sonorous body can be added, or displaced, without influencing sound. It is also remarkable that an old building, intended for so foreign a purpose, and so rude, should be found more demonstrative of the economy of speech than all the works of art that have been intended for this purpose.
instance of the class-room of a man of science, formed of similar materials, and producing similar effects as in Canon Mills.--I shall now give another instance of rude and rugged materials producing similar effects, from similar causes, by moderation of action and sound. A celebrated physiologist, in his examination before the last Committee of the Cominons, on the transmission of sound in apartments, &c., alludes to a particular class room, as constructed on scientific principles, and well adapted to the purposes of speechi. In it the floor is of earth, the walls of solid and rough masonry, the roof is of unplaned plank, covered above with a thick coat of compost, and supported in the central parts by pillars of brick, in their original porous state: all being comparatively solid, and rough on their exteriors. The only material difference that I can perceive, is, that the old gas house, Canon Mills, is a matter of chance in regard to sound; whereas the learned doctor's class room has been constructed by a man of science; they are indeed very different in form, and yet form is the only point that architects seem to consider of importance in imitating Canon Mills. One advantage in both these places is, that There is little glass exposed to the voice of a speaker.
The materials used in Canon Mills, the physiologist's class room, the meaniest cottage, or even the barn, are alike.
Erroneous to suppose that Undulatory Action should be lengthened, and Reflections prolonged.—The learned doctor, in his further depositions, recommends that the reflections of speech, in the Houses of Parliament, should be taken from the ceilings, transversely to the direction in which the human voice proceeds from the mouth; the direction being horizontal whether we sit, or stand. He also advises that the ceilings should be formed on the principles of a piano forte sounding board ; thus increasing and prolonging sound, and the reflection of each letter more decidedly than the copyists of Canon Mills.
It may now be proper to ascertain by what means the principles by which the retlecting bodies, in these two apartments, are less ungenial to articulation, than where such are more sonorous and refined in appearance, as this may lead to the beneficial vise of materials possessing similar properties, but less offensive to the eye.
Reasons why Speech is less indistinct in Canon Mills and the physiologist's class room than in more refined apartments.-Doctor Neil Arnot reinarks, that when sound is reflected by a solid, the angle of incidence and reflection correspond; and he illustrates this by a boy's hand ball thrown against a wall, when the angle of reflection is equal to that of incidence. But the analogy applies only in a limited degree, because the ball is kept together in mass, whereas, the component parts of the atmosphere are scattered and divided, and so is sound, as our sense of hearing tells us. The greatest repelling force is, no doubt, in one direction, but the matter that gives effect to sound passes, in a certain degree, in all directions; the particles in the atmosphere impinging on a rough surface, press in various directions, in conformity to the minute angles presented to them, and consequently occasion less vibratory and undulatory action in the reflecting body than when the surface is smooth, and the pressure in one general direction. The component parts of the atmosphere thus recoiling in various directions, strike upon, oppose each other, and from this cause also lessen the sound. If the ear be near to such rough surfaces, they occasion harsh sound to be transmitted to the nerve of hearing; but at a little distance, the atmosphere again runs smooth, and produces no such effects.
I would next observe, as to the earthen floor, that the action and sound from it are much less than from hollow boarding ;-the earth is comparatively soft, little elastic, and rough externally-for these reasons, sound from it does not sensibly affect the ear, nor cause any reaction from the roof. These facts may be learned from the ground in general producing no confusion either in speech, or music. The earth has also an action different from hard bodies of limited thickness, such as boards, lath, and plaster, by which motion and sound are lessened in these materials.
Angular Surfaces calculated to prevent extraneous sounds from reaching the ear.— The apartments just alluded to, are, I conceive, better calculated to demonstrate, by the rough surface and comparative solidity, the means by which harsh and ungenial reflections may be prevented from reaching the ear, than to exemplify the manner in which consistent reflections are to be obtained.
Instances of extreme confusion, prevailing for years, without any attempt to remedy this.-In order further to point out the difficulties that have been experienced in forming, and in copying rooms intended for speech, I would refer to my pamphlet on the Economy of Speech in Apartments, in which instances are pointed out, in various localities, where utter confusion prevails. Two very remarkable instances are, the church in Edinburgh, in which the General Assembly of the Church of Scotland met several years ago, but which they were compelled to desert, because they could not understand each other; there is great confusion throughout, and two of the galleries bave ever since been locked up; nor has any attempt been made, so far as I know, to reclaim these. The other is St. Luke's Church in Liverpool, where the patrons have been rolling the incumbent from place to place, for a series of years, in a locomotive pulpit, with a drum canopy over it, thus increasing the evil wherever they go, instead of remedying it. If the matter be simple, as many say, why has not speech been rendered intelligible in these two edifices?
Sound reflected from Sonorous Solids in Apartments, in at least six directions, must necessarily confuse Speech.-It may be remarked that an apartment for speech being a work of art, in wbich solids are in a limited space, and most of them sonorous, when from the human voice, or any other cause, sound is produced by rapidly agitating the atmosphere, it impinges on, and recoils from, the sonorous solids, on the walls, the floor, and the ceiling, in at least six different directions; and if the agitation be great, the effects are similar to what is produced in the ocean, when waves meet from various directions in a small compass, occasioning, by their conflict, confusion in sound, as it has already done in the atmosphere, by which it is conducted.
There are various ways of exemplifying this in apartments, and in the atmosphere, where sound is not confined.
All Curvatures, by concentration, confuse Speech.-Notwithstanding that all writers on this subject, so far as I have been able to ascertain, recommend excess of sound, and several advise its concentration, or being made to act in foci, wherever the human voice, in speech, acts within a curvature, articulation is deranged, and the greater the curve, and the more sonorous the material, the greater is the perturbation.
The evil of extreme agitation, by changing the original character of sound, is exemplified in that of a bell, the sound of which is most clearly, intensely, and distantly heard, when there is an extremely light current of air moving from the bell towards the ear; but if the wind be strong, the component parts of the air are deranged, and sound is not heard so intensely, distinctly, or distantly.
Sonorous Solids conduct Sounds generally with velocity and intensity in a similar ratio, but in air it is equal in Velocity and Character throughout.-Sonorous solids are considered to conduct sound with velocity, much in the ratio of the intensity with which it is produced-concrete plaster 11 or 12 times, and glass and fir wood with 15 or 16 times its velocity in common air. In the atmosphere it passes with equal velocity in all directions, if no more dense medium should intervene between the source of sound and the ear, and it is conducted without change of character. In solids, its character and direction are changed, and the degree of sound depends on the density of atoms, and their distance from each other. When sound reaches a solid, its direction and character are changed, from various causes, according to the nature and form of the solid. It is produced by cohesion, repulsion, and friction in the atoms, and the degree of sound is, therefore, in a great measure, dependent on the density of the atoms, and their distance from each other; thus, silver and gold are less sonorous than copper, bell metal, or glass; and lead, which is peculiarly soft, is less sonorous than any of these bodies.
Sound acts similarly in the Musical String, and in Wood of long fibre.—There are other properties and arrangements in certain materials, which appear to operate, by their cohesive and repulsive principles, most powerfully in one direction ; for instance, in
vood of long fibre it acis predominantly in the direction of the fibre, similarly to that in the musical string.
Not only do these circumstances lead to a knowledge of the degree and character of sound emitted from various bodies, and tell us that every atom acts its part in producing it; but an understanding of all these points is necessary for the control and guidance of this singular phenomenon.
Sound being produced in Solids, acts throughout all their atoms. -On striking a solid, so as to produce sound, every atom in it is set in motion, and if another sonorous solid be in contact with it, similar effects are produced in the second as in the first solid, until by friction the atoms are brought to rest, when sound also ceases.
Predominating influence in the solids, but air also necessary to produce Sound.-For the reasons given, in the solids* usual in apart* Professor Liebig says, that every atom in the earth has its own atmosphere, and every
ments, sound operates with more intensity and rapidity than in the atmosphere alone, (although the solid must be in contact with air,) but the predominating influence is in the solids.
It is evident, from these and other understood facts, that it is in the solids in and sạrrounding an apartment, that sound must be regulated.
Cross Sounds not admissible, doc. Necessity of regulating Undulation in the solids. I have already explained that neither cross sounds, nor excessive sound, is admissible, and that reflections which reach the ear must fall on the pinna horizontally—that the undulatory motion in the reflecting bodies must be regulated; and I shall further demonstrate the means by which this is to be effected, and those by which cross sounds are to be withheld from the ear, without exposing soft non-sonorous materials, so as to arrest the tremulous atmosphere and sound generally in an apartment. I have certainly explained enough to convince the most sceptical that it is preposterous to imagine that all that is requisite to be attended to is the mere form of a room, or that materials may be thrown together indiscriminately, conducting and reflecting in various directions, and in any degree. As sound passes with equal velocity in all directions in the atmosphere, the first solid that the voice of a speaker must operate on, is that nearest to him, and, being conducted with so much greater rapidity by the solids than in air, it must pass by the solids, and by these be given out to the atmosphere.
Effects of the predominating velocity and intensily of Action and Sound in the Solids. For instance, supposing an apartment eighty. five feet in length, and half this width, and that the speaker is placed in one end against the wall, the sound of his voice passes by the atoms of the solids in the walls to the other end of the room, when it is only a few feet from his mouth in air, and as undulation succeeds undulation with so much greater rapidity and intensity of effect in the solids than in air, the predominating influence must be in the solids.
Prevention of Echo insufficient to economize Speech.—Many suppose that preventing echo and a repetition of reflection is suficient; but this is only a palliation of the evils experienced, because a single reflection, although it may be prolonged too much, is less prejudicial than a repetition of reflection.
For the reasons given, irregular reflections of the voice and extraneous sounds are so general, that, although the ear may not be sensible of these individually, they interfere more than we are aware with those which convey distinct and intelligible sounds to the nerve and sense of hearing.
Further general observations.-In different phenomena, causes and effects vary; but, reasoning by analogy between hearing and sight, I would remark, in regard to the faculty of vision, that, if the atom in the finest metal must have its own atmosphere to produce sound. He also remarks, that cork and India rubber have done more than any thing else, in the course of the last fifty years, for the improvement of chemistry; and such bodies as these, buff leather and woolen cloth, may do much for the economy of sound.