Document rBKg6OnBBdEqQ1y3B0X4r8Gba

HEATINC VENTILATING AIR CONDITIONING GUIDE 1943 Table 6. Weights of Sheet Metal Used for Dpct Construction u. s. Std. . Black Sheets Approximate Thickness, In. Weight Per Square Foot ' " ' Galvanized Sheets!* Approximate Thickness, In. Weight Per Square Foot Steel Iron Ounces Pounds Steel . Iron . Ounces Pounds 30 0.0123 0.0125 8 28 0.0153 0.0156 10 26 0.0184 0.0188 12 24 0.0245 0.0250 16 22 0.0306 0.0313 20 20 0.0368 0.0375 24 18 0.0490 0.0500 32 0.500 0.625 0.750 1.000 1.250 1.500 2.000 0.0163 0.0193 0.0224 0.0285 0.0346 0.0408 . 0.0530 0.0165 0.0196 0.0228 0.0290 0.0353 0.0415 0.0540 10.5 12.5 14.5 18.5 22.5 26.5 34.5 0.656 0.781 0.906 1.156 1.406 1.656 2.156 16 0.0613 0.0625 40 14 0.0766 0.0781 50 12 0.1072 0.1094 70 11 0.1225 0.1250 80 10 0.1379 0.1406 90 2.500 3.125 4.375 5.000 5.625 0.0653 0.0806 0.1112 0.1265 0.1419 0.0665 0.0821 0.1134 0.1290 0.1446 42.5 52.5 72.5 82.5 92.5 2.656 3.281 4.531 5.156 5.781 ^Galvanized sheets are gaged before galvanizing and. are therefore approximately 0.004 in. thicker. , Table 7. Weights and Thicknesses of Standard Copper Sheets'^ ' '_________________________ Rolled to Weight____________________________ Weight per Square Foot Thickness, Inches Nearest Gage No. Ounces Pounds Decimal Equivalent Nearest Fraction B. & S. Stubs U. S. Std. 10 0.625 0.0135 12 0.750 0:0162 /^4 14 0.875 0.0189 16 1.000 0.0216 )^2 18 1.125 0.0243 i'i 2 20 1.250 0.0270 %2 24 1.500 0.0324 M2 28 1.750 0.0378 M2 32 2.000 0.0432 Hi 36 2.250 0.0486 -Hi . 40 2.500 0.0540 Hi 44 48 . 56 64 2.750 3.000 3.500 4.000 0.0594 0.0648 . 0.0756 0.0864 . Me Me Hi Hi ^Variations from these weights must be expected in practice. 27 26 25 23 22 21 20 19 17 16 15 15 14 13 11 29 . 29 27 28 26 26 24 25 23 24 22 23 21 22 20 19 18 17 . 20 19 18 17 17 16 . 15 14 17 16 14 13 is considered good practice to allow 20 per cent additional for weights of joints and bracings. Various weights andx thicknesses of standard copper sheets will be found in Table 7. REFERENCES Method of Determining Rectangular Equivalents and Weights of Ducts, by Peter Franck (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, December, 1940). The Flow of Liquids, by W. H. McAdams {Refrigerating Engineering, February, 1925, p. 279). . A Study of the Data.on the Flow of Fluids in Pipes, by Emory Kemler (A.S.M.E. Transactions, Hydraulics Section, August 31, 1933, p. 7). Air Conditioning and. Engineering, American Blower Corp. Fan Engineering, Buffalo Forge Co'. , Heat Power Engineering, by Barnard, Ellenwood, and Hirshfeld, Part III. Mechanical Engineers' Handbook, by Lionel S. Marks, McGraw-Hill Book Co. 624 Chapter S3 SOUND CONTROL Unit of Noise Measurement, Apparatus for Measuring Noise, General Problem, Kinds of Noise, Noise Transmitted Through Ducts, Design Room Noise Level, Noise Generated by Fan, Natural Attenuation of Duct System, Duct Sound Absorbers, Air Supply Noises, Grille. Selection, Cross Transmission Be tween Rooms, Controlling Vibrationfrom Machine Mountings IN ventilating and air conditioning a building or a room, the effect of the mechanical system employed must be considered on the acoustics of the space conditioned. It is important to consider also that the use of air conditioning often permits keeping the windows closed, thus giving relief from certain external noises, but at the same time increasing the necessity of providing adequate sound control. . It is not assumed that the ventilating and air conditioning^ engineer will attempt to improve the acoustics of the space that is being con ditioned, but the designer should have at least enough fundamental knowledge of the acoustical effects of the system which is being designed to be sure that no damaging effects occur to the existing acoustical properties. It is assumed that in a given space the architect and acoustical engineer have produced a room or rooms which are satisfactory for speech, music, or other uses. The ventilating engineer's sole function is to ventilate and air condition these rooms properly so that they will be physically comfortable without adding any acoustical hazards. UNIT OF NOISE MEASUREMENT By a recently adopted international standard, two terms are used for noise measurement. The decibel (db) is the physical unit for expressing intensity or pressure levels. The phon is the unit of loudness level. The loudness level, in phons, of any sound is by definition equal to the in tensity level in decibels of a thousand cycle tone which sounds equally loud. The decibel is defined by the relation N =. 10 log where N is the number of decibels by which the intensity-flux I-, exceeds the intensity flux I0. The intensity flux is the measure of the energy contained in a sound wave and is defined in terms of micro-watts per square centimeter of wave front in a freely traveling plane wave. It is usually more con venient to select an arbitrary reference intensity for I0 and express all 625