HONG KONG DAILY PRESS, SATURDAY, OCTOBER 3, 1931.
Use Green Island Cement
for
Constructural Work of
Every Description.
HOW GREEN ISLAND CEMENT IS MADE
Green Island Cement is manufactured from hard limestone and clay. It is necessary that these materials should be finely ground in order that they may come into intimate contact with one another in the burning process.
The finely pulverised materials are mixed in a certain detinite proportion, roughly one part of clay to three of limestone, and are fed to the Rotary Kilns.
In these kilns they meet the hot gases and flames generated by pulverised coal blown in at the other end of the kilns, and after various chemical actions have taken place, they combine to form Portland Cement Clinker...
The Clinker is ground down, with a small percentage of gypsum to regulate the setting time, and Green Island Portland Cement is thus. produced.
Although sounding so simple, in reality the process is an intricate combination of mechanical, physical and ebemical operations, needing great skill and care, Nothing but constant and accurate supervision will yield the results so well-known with Green Island Cement; namely, strength, uniformity and reliability.
USE GREEN ISLAND CEMENT
Issued by the
ENGINEERING AND
THE ACOUSTICS OF BUILDINGS.
APPRECIATION OF TECHNICAL PROBLEMS IN CONSTRUCTION."
TAKING ADVANTAGE OF RESULES OF
RESEARCH AND EXPERIENCE.
In view of the examples of acous | Papers on Acoustics" extend over tically defective halls which abound the period, from 1000 to 1918, and in our towns and cities, it is the work and that of others has more surprising to find that the
attracted considerable attention fundamental principles of architec- both in the United State, aud tural acoustics were clearly appre
Germany. ciated nearly a century ago in As a consequence, although much Great Britain by a number of remains to be done, there is now workers. Then, an now, it was sufficient volume of experience to realiseil that the two defects most enable the main acoustic require frequently..met with a large audiments of a building is even com-
A
toriums are (1) echoes and (2) menced. excess of reverberation; that is, the tendency of an arrested sound to persist unduly by multiple re- flection at the boundaries, owing to their deficient absorptive proper
ties.
space.
Dickens's acoustic powers of ob servation are exampliled in "Mar- tin Chuzzlewit," written in 1843,
11
for stordhouses, 27
were
BUILDING
Loudness.
In passing, it may be added that there does not appear to be any recorded scientific evidence that
TALL BUILDING MOVED BODILY.
stretched wires exert any beneficial BUSINESS UNINTERRUPTED effect in auditorium acoustics, use is made of the analogy between
though examples may still be fopad At Indianapolis recently the water ripples and cylindrical sound echo and revorheration, the ques diana Bell Telophone Company, an In addition to the defects of general office building of the In. waves, a method which appears totion have been first suggested by Scott almost certainly arise in a large 11,000 tons, was moved 52 feet, and of inadequate loudness will eight-storey structure, weighing! Russel at a meeting of the British building, particularly in the case then turned through an angle of site advantages, and both give the range of the unassisted speak activities in the building went on Association in 1863. Each method of speech. Experience agrees that 90 deg. During the move all the results which, although predictable ing voice of average strength is of as usual. Evelators continued to in: the
mean by geometrical the order of 50 feet, that is, pro-run, gas, steam hent, water, electrio methods, show also the apronding vided the hearer is so situated as power, and drainage facilities were of waves by diffraction beyond the to receive a direct 'ray of sound. maintained by flexible connections optical limits. Incidentally, either At greater distances it becomes and long-distance telephone circuits of the experimental methods is more necessary to provide reinforcement, were operated without interruption. convincing than the geometrical either by reflection from suitable of service.
when for any reason it is desired surfaces, or by an electrical loud-
the acoustic properties of a particreasing use that is being made of It carrying out the operation a to provide goular demonstration of speaker system. In view of the in- cular architectural design.
raparatory Mark,
public address system, it should be concrets mat was laid as basement realised that their main office in level over the entire area over a large hall is to provide adequate which the building was to be moved. loudness in the remoter parta. Eur. Over this Bin by Bin fir timbera ther, by placing the loud speakers were, placed, and on top of them some ceiling echoes may sometimes in part to form the surface in suitably high positions, trouble steel railroad rails were laid about
remedy for be obviated: The system is not a
loudness adds to the confusion. The were voted to carry the load of on which the building moved. excessive reverberation, On each of the 59 columns on the contrary, the increased supporting the Building I-beams
Reverberation. As alrendy
remarked, the cou inon defect of largo auditoriums fa porous walls have, on Rayleigh's undúo reverberation: Rigid non
for cound than the best mirrors estimate, a higher reflecting power have for light. Thus, unless ab-
provided, the rate of dying away sorptive
of a sound in a large hall will not mally be so protracted us to cause confusing overlapping, of successive sound or syllables emitted at or dinary rates.
materials in some form are,
He es
Use of Jacks. For the 52ft, movo 18 100-ton and
The principles are simple and
tivo when stops have been taken to the rollers. These were placed straightforward, but much scop
reduce reverberation by introducing under two steel rail shoes on each system may be a valuable corree the lead of the stoel columns to ticism and apathy will have to be
absorbent material procedure side of the column, the average dispelled in Great Britain to pre
which of itself unfortunately de number under each shoe being nine, vent repetition of the acoustical failurea conspicuous in a number So long ago as 1835, at a meet- of modern halla. The Press reflects
creases the
Ho vohime of pund. It while the total exceeded 4,000. ing of the British Association at the view commonly held the archi
hus, of course, to be, recognised that Latticed trusses or I-beams tied the Dublin, we find Reid recognising tectural acoustics is a gamble. For Sabine that has made it possible to amplifier and loud-speaker may not tary diagonal, bracing, sa that no It was primarily the work of in some cases the rendition of an columne together with supplemen reverberation as a prevalent acous oxample, the Times on July 24, miensure the proportion of incident be wholly acceptable to a cultivated shift in the relative positions of the tic defect and suggesting remedies 1022, remarked that: "Broadly
sound energy absorbed by a mato-ear. The amplification should not columns was possible. This work in the shape of more absorbent speaking, it may be said that, the
rial (that is, the walls by increasing their roughness acoustic qualties of a hall or room power), or to predetermine the will result, nor should the different steel..
absorbing be exeresivo or unnatural effects required some 600 tons of structural or irregularity, or by hanging cannot yet be predicted ";" and
amount of absorbent necessary loud-aponkers bo widely separated draperies. He also stressed the ad again in its issue of October 19, to ensure acceptable reverbera or effects of repetition akin to scho vantage of excluding superfluous 1920, it was stated thatthere is on in a hall If a steady source will be produced. In Great Britain-ton ratchet screw-jacks were no means of studying the acoustic of sound in a room is suddenly the system has so far been installed used. These were placed laterally properties of a building which does stopped, then Sabine showed that notably in large cathedrals, egy between the I-beam construction on not exist, or exists only on paper,"
the duration of audibility (when Liverpool Cathedral, Westminster the columns and the rear retaining However, within recent years the tions) is an important acoustical native method of amplification is side basement wall was left stand-
determined under proper condi- In Chap. is, in describing the subject of applied acoustics, as a characteristic of the room
Abbey, and Bath Abbey. An alter wall, and part of the extreme out- Houses in the neighbourhood of quantitative science, has become the tablished the reintion that this re- where certain seats are equipped the jacks were roset, and the brad Todger's boarding-house, he relates / object of study at a number of verberation period (as it is called) with sar phones, for the purpose on which they rest was built up. employed in the House of Lords, ing. After each foot of movement These mandiong, now only used centres in England, notably the is proportional to the volume of of affording assistance to individual with timber. When the building dark Signals Experimental Establish the room, and inversely propor- auditors who suffer from dealness had reached the extreme southerly and dull, and, being filled with ment at Woolwich, the National tional to the total absorbing power wool, and cotton, and the like Physical Laboratory at Teddington; such heavy merchandise at stiflea and the Building Research at Wat
point of its travel the jacks were placed under each column to re- We may proceed to review some
its optimum reverberant condition, of the rollers and steel rail shoes We see that for a room to attain lieve the pressure, and the positions of the acoustical characteristics of
it is necessary to arrange that were changed so that the former a. building,
that the various exposed surfaces pointed toward the pivotal point. shall possess in the aggregate the near the south-west corner of the The degree of everberation is require to know this absorption co-direction in which the building was roquisite absorbing power. We thus building, or at right angles to the all important, sertain amount efficient or the absorbing power of to be moved. Actual rolling of the leads to greater loudness but in- is pleasing and helpful; excess
unit area of each material present. building was accomplished as before cressed confusion; insufficient reployed for measuring this co strategic points to push the mass Various methods have been in with the lacks placed laterally at sults in enfeeblement and staccato efficient of absorption for building in the proper direction, their efforts effects which are displeasing to and other materiais. One method being supplemented by a pulling hearers and, furthermore, impart is to measure the change in the force supplied by a stationary steam power to a speaker of anger. A test chamber when a known and stranded steel cables. a sense of deadness or absence of reverberation period in a calibrated engine and tackle blocks using great variety of observations have suitably largo area of the material been carried out on the optimum is introduced under proper con- reverberation periods to suit dif. ditions. In a second method, a Terent conditions. Briedy, it may beam of sound is directed towards made to provide access to the build- all hails (up to, say, 50,000 cubic in an aperture in a sound-proof A curved steel and concrete side- be said that for speech in relatively a test specimen mounted as a paneling during the moving operation. foot) a period of about one second wall, and the proportions of the walk was constructed and connect
GREEN ISLAND GEMENT CO., LTD.
GEMENT CO., LTD. sound and stops the throat of echo- for ma
2ND FLOOR,
EXCHANGE BUILDING."
DUSSEAL.
MAKES PAINTING
POSSIBLE ON NEW
a. Berger Product
WALLS, AND IS AN EXCELLENT OURE FOR DAMP WALLS.
FOR FURTHER PARTICULARS APPLY TO
OXLEY & CO.
W. R.
BUILDING, CHATER ROAD.
PRESERVING MSS.
had, an air of palapable deadness. about them."
Roger Smith, in his Acoustics of Public Buildings." (1831)," re- marked that: "In empty houses a
great reverberation is" perceptible
which diminishes as the flours are
Echoes.
As regards echoes, it is found that taceho becomes noticeable
when the reflected sound laga be
sovered with carpets and the rooms Find the direct sound by more than filled with furniture." Tyndall, in about 1-18 second. If the lag is 1808, in evidence, before a Select less than this, the reflected sound Committee of the House of Com-will serve to reinfores the direct mona stressed the value of a low sound. This is an argument in ceiling as a reinforcing device, and favour of limiting the heights of the influence of an audienco and the ceilings of councils chambers of draperies in quenching the after and the like to not more than about sound. During the proceedings of feet, as the ceiling is the only this committee, it was elicited that reinforcer.common to every speaker flock paper applied to the walls of no matter what his location. The a reverberant room had proved an House of Commons serves as an
effective remedy.
Again, Johnetone Stoney (1885)
described how be tested a room
illustration.
Thus the question of schpes will not arise except with large halls,
of the boundaries and contexts. If we work in square feet and
ality is. 1-20. It enay be noted that seconds, the constant of proportion the relative linear dimensions of a room are not now regarded as
treme shapes material, except perhaps for ex
Absorption Coefficients;
Artifcial Bidewalk. Elaborate arrangements
Were
which had its walls papered ore though even h light ccho may con is preferred, the value.increasing incident sound which are reflecteded to the main entrance by a species.
that the programme for two days was by porous rigid bodies. Furthermore, interference phono was completed in one...
up to about two seconds for the or transmitted are measured. largest halls Cultivated musical Figures for the absorption co opinion agroes in preferring rather ofcients of a number of materials
of drawbridge which pivoted as tho building moved,, the bridge being moved and fastened in a different
a lining of canvas, the canvas being
tribute to poor hearing. The effect a short distance in. front of the
is not likely to be pronounced in framework over
the absence of smooth concars which it was
aur. faces, such naa dome or barrel. atretched. From his experiment he inferred that concert halls or public
vaulting, which lead to unevenne periods for music, depend-have been determined by Sabine and position on the sidewalk as requir
ing on its character and volume. rooms could be effectually freed
mund distribution an
and are definite-
others. Per square foot, they range
ed by the progress of the work. Be- from echo effects by the simple ex inimical to good acoustics. Such It may be remarked that in large from 1.0 for an open window, 0.5 fore the move seven submarine-typo pedient of lining the walls and
surfaces should be broken up, for cathedrals and churches, reverbera for hair-felt one inch thick, to cables were pulled into place and ceiling in such a manner.
example, by coffering, and the obtian periods up to six or seven or about 0.01 for plaster or glass, spliced to the 642 long-distance tele- jectionable reflections absorbed by moro seconds are common, a con- Fach folated member of an oud phone circuits entering the build. Rayleich, in the second edition of suitable means. A satisfactory dis dition which dates back to medieval enco is equivalent in absorbinging, each being gise more than 200 his Theory of Sound" (1828) tribution of sound may normally times and is responsible for certain power to about 41 square feet of feet of slack save the first mathematical treat be anticipated within a ball of ap features of the servicca-the charac open window. In the majority of mont of the absorption sound proximately rectangular, section. teristic choral and organ music, the cases the audience constitutes the
intoned liturgy, and the frequent most absorbent featurs in a ball, proof room may well be construct clearly recognised the inevitability:
inaudibility of the speaking voice so that the reverberation period is ed like na inuer box which is float- of reverberation in large, roome Dr. W. W. Bishop, of the Uni-
The remedy for excessive rever- with non-porous boundaries, and versity of Michigan, U.8.A., re-suggested a remedy in the shape The reflecting characteristics of the dure the volume, if practicable,
markedly responsive to the size ofed on insulators on the structural beration in a room is either to re- the audience. ferring to a report on the precer of thick carpets, curtains, eto
floor, and overywhore insulated The effect of economic depression Faxa
from the structural walls and ceil on the work of libraries through:vation of manuscripts and books,
boundaries of an auditorium may,nay, by lowering the colling and described experiments which" are
The ground would seem to have with a little experience, be approxi- | partitioning off unnecessary large
ing. the Presiding of the International being carried out in America to ne prepares for a systematic mately appraised from a geordetrical recesses, or to increase the sound Federation of Library Associations, inds of paper in varying tern.
test the durability of different investigation on auditorium acous study of sentions based upon the absorbing power of its surfaces by tice in England, but it was not optical inws of reflection. Two the use of absorbents such as felt, M. Collign, of Stockholm, at the
forthcoming, and it is to the other methods are annual meeting of the Federationperatures.
available for use quilting, wood wool, acrated pins pioneer work of the late Professor with scale-models. In one, Arattor, fibre board, carpets, curtains, at Cheltenham.
"This problem of preserving w. C, Sabine, of Harvard Univer-used by Sabine in this connection upholstery, etc. In some cases the case of structure-borne sounds, it erected Preventive treatment
sity, that we must turn for the first in 1913, the progress of
by Sabine in this counts elucidation of the main practical soundpulse in the model is display can be so chosen that they will nlio to Int
actual disposition and shape of absorbents problems, particularly as regards ed by the well-known, method of serve to suppress undesirable reflec structure.
Collected, spark illumination. In the other,
PERIMENTS CARRIED OUT
IN AMERICA,
out the world was referred to by
The fifteen delegates represented twelve nationalities, and so quick ly did they transact the business- each speaking in his own language
manuscripts and books," he said, is a very serious one specially in cooler climates where artificial heat is used in the libraries.”
rever)
mena are not likely to be of any moment, particularly in the case of sproch.
To conclude what it only a partial
Sound-proofing..
is often of great practical import survey of the subject, it is evident
question of sound-proofing
anco-As regards the transmission that neglect of the established prin- of air-borne sounds,
are bent arrested by
ciples may lead to defective acoUS, ficiently massive, and rig
ing... walls suftio conditions which may prove
In the incurable after a building is
taples ta, purative, and archi
the tests should be prepared to
allow
nucd nt foot of next colum.
acoustio requirements some share in influearing their deargom