Document eNRddGQvro91MxVnZj0mye3m

American Society of Heating and Ventilating Engineers Guide, 1936 Room loudness = 10 logic 10 = 10 db If the sound absorption in the auditorium had been as small as 200 sabines, the sound intensity in the auditorium would have been 10 times as great and the noise level in the auditorium would have been 20 db. If the rest, of the auditorium has an area. of .20,000 .sq ft with a surrounding noise intensity of 50 db (/" = 10s) the noise level due to all ot the noise entering through the wall would be found as follows: = 10s X 0.00001 - 1 :, = 10 (Through equipment wall) + 1 X ^200(3^ = ^ Room loudness X 10 logio 20' = 13 db Now suppose that there is also a duct having 20 sq ft outlet connecting the room with apparatus having a noise level of 70 db (/" = 107) and suppose that there is an assumed attenuation in the duct equivalent to a transmission factor of 0.0002. Then, -f- = 10r X 0.0002 = 2 X 10* T 1 -20 --j-- -- 20 (from above) + 2 X 10* X 2000 = ^ ' Room loudness = 10 logio 40 --10 db ' ;"* 1 It may be seen how the energies of noises entering a room are added to obtain the final room noise intensity. : .,, T ;'" `j .." ' i 1 ' ` 5 The average coefficients of sound transmission (128 to 4096 cycles) for a number of walls and of floor and ceiling partitions are: listed in Table 3, Table.3.; Average!Coefficients of Sound Transmission for Building Partitions? , ;, ; .` DESCBimbN 0? Partition 1, Average- 'QOEFFICrEST Brick' parjel, Mississippi;&mi; plastered'both sides gypsum browncoat, smooth: white finish; good workmanship.......................... 0.000010 ' Brick wall, 2}4-in. plaster both sides..................-- ----------;----.-- ; o.pooo32 Brick wali,'2H-m., 2-in. furring strips, H;`n..rigid.insuIation iath plastered botp sides.:-...-...J,::------------.1--............ ....... 0.j3000(n(> Brick' wall, 4 in.) 2-in. furring strips and J$-in. rigid insulation lath, plaster, 0.0000040 Concrete flat slab fljoor cdnstrtictiori,' reinforced*?; floating floor; consisting of .nailing: strips, rough and'finish flooring; ^-ln.rigidmsulationfurred 0:0000020: 0.0010 Glass, plate fj-ih. double glared, lM-in. separation...--.............. ------- ,-- VO,0001 Metal: lath, double,| onlJl-inL channels, %:in. gyjp^^;i>Udter^\niEout cross bracing clipS; 4 in., cohnected at_edges only........ 0.000016; Tile, hollow day-partition, three cells, 4 in. x 12 in. x 12-m., wood-furring strips, }^-in. dgid insulation; gypsum brown coat, smooth white finish.-- 0.0000050 Wood joists, lower side plastered on: wood lath; floating floor consisting of nailing strips) -rough and finish flooring------------------....;........... ------ :------ - Wood studs, two Ji-in. sheafs rigid insulation both sides, joints filled; gypsuni scratch and brown coats/smooth white finish------ ------------------- 0.0000050 0.000013 Wood studs, 2 in: x 4 in., -g3T?stin:,plaster; 0.000040 . aArchitectural Acoustics, by V. O. Knudsen, pp. 308-322;^. 332 ;, Chapter 18--Sound Control LOCATION AND INSULATION OF EQUIPMENT ROOM The equipment room, if possible, should be located at a considerable distance from all rooms in which quiet is required. If this is not possible; it is necessary to provide a high degree of insulation against the noise which may be transmitted through the walls of the equipment room, and also against the noise which almost certainly will be communicated through the short ducts. (See discussion of Control of Noise Trans mission through Ducts, p. 337). Three wall sections and two floor and ceiling sections which' are satisfactory for the wall insulation of the equipment room are shown in Fig. 2. Other partitions, with their sound insulating values, are listed in Table 3. The addition of absorptive materials (such as are described in Table 2) to the inner walls and ceiling M. ^ "^4 Bnck 'z < iIZ *'l Plaster Insulation Value947 db 4 Hollow-Clay Tile l"x 2" Furring Strips Paper and Metal Lath Plaster Insulation Value - 52 db. Absorptive' Blanket l" P2 Fibre Board Insulation Value Greater than 50 Pdbla.ster -Staggered Wood Studs - -^Absorptive Blanket----Plaster on Lath Insulation Value 50 db. 3 ^Concrete Slab Resilient Hangers t Plaster on Lath insulation Value9 60 db'. or more Fig. 2. Three Wall Sections and Two Floor and Ceiling Sections which are Suitable, for the I nsulation of Equipment` Rooms3! ^Acoustical.Problems, in the Heating and Ventilating of Buildings,-by V; O- Knudsen (A5.H.VE Transactions,'Vol. 38; 1932); s' of the equipment room will not only increase the-insulation through the walls, but will also -reduce the intensity-of the noise in the room, -The equipment room noise intensity may be figured in the same way as.that of the conditioned spa.ee, taking the equipment as the source of noise. ;.In case the equipment is subject to considerable vibration it is advisable to provide a separate or floated floor. . : INSULATION OF MACHINERY AND SOLID-BORNE VIBRATION Since mechanical vibrations are readily transmitted through the solid structure of a- building, it is extremely important in air conditionihg that all mechanical equipment in which vibrations are generated be- thoroughly insulated from the solid structure of the building: An almost universal notion prevails that the vibrations generated by machinery can be in sulated from a building simply by placing a slab of cork or a layer of hair felt between the machinery' and the floor- of the room. If the ma chinery is sufficiently heavy, and the cork or felt sufficiently resilient, this expedient may suffice. On the other hand, if the machinery is not suf ficiently heavy to load the cork or felt support to the extent that the 333