1、1997 GUIDELINE for Al R-CONDITIONING shutting down operation of air-conditioning units (angry owners), larger lot sizes, relocation of units, expensive noise umtrol measures, and finally, the added enforcement costs. Each community must determine its own particular characteristics in order to includ
2、e ail of the important factors so that the ordinance is realistic and practical in terms of both sound levels and cost. A consultant may be required to help with the more complex situations. FROM NORMAL POPULATION LOW Sound Pressure Level HIGH Figure 1. Community Response as a Function of Sound Pres
3、sure Level 3 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STD-AR1 GUIDELINE L-ENGL 1777 0352320 OOLLL30 358 AR1 GUIDELINE L-1997 1 Table 1. National Estimate of Outdoor
4、Background Noise Based on General Type ,f Community Area and Nearby Automotive Traffic Activity Nighttime, ral, no nearby traffic of concern 1 Curve No. in QO. Condition I I 3 Nighttime, suburban, no nearby traffic of Daytime, suburban, no nearby traffic of Nighttime, urban; no nearby traffic of con
5、cern 4 concern 5 concern 2 3 3 2 IDaytime.ral;noneartytrafficofconcern I 2 I 7 8 Nighttime, business or commercial area Daytime, business or commercial am 4 5 9 10 Nighttime. induhai or manufacturing area 5 6 Daytime, induhai or manufacturing area i 1 12 13 171 14 Within 300ft. 91.4 m of continuous
6、heavy- I density traffic Within 300 ft. 91.4 m of intermient light traffic route Within 300 ft. 91.4 m of continuous light traffic route Within300ft.91.4mofcontinuous 6 m&um-densitv traffic 3 4 - 15 300 to loo0 k 91.4 to 304.8 m from intermittent light traffic mute. 16 300to 1000fL91.4to304.8mfrom c
7、ontinuous light traffic route 17 3tolk91.4to304.8mfrom continuous medium-density traffic 18 3to1000ft91.4to304.8mfrom I continuous heavy-deasity traffic 2 3 5 continuous mediumdensity traffic continuous heavy-density traffic Section 7. Use of AR1 Standards 270 and 275 7.1 A well-planned community so
8、und ordinance will establish acceptable sound levels which any new or replacement construction must meet. Within the air- conditioning industry, ARI Standard 270, is widely accepted as the preferred procedure for determining the md rating level of the outdoor sections of residential size unitary equ
9、ipment. AlU Standard 275, describes a procedure for applying these sound rating levels to practical real-life situations. Through the use of ART Standard 270 and ARI Standard 275, the contractor, developer, or homeowner can estimate whether the equipment to be instailed will meet an existing sound s
10、pecincation. If the predicted level is too high there are severa options available, however, the number of options become quite imited once the air-conditioning unit is instaiied. in order to use ARI Standards 270 and 275 to their best advantage, a thorough understanding of each of these Standards i
11、s recommended. ARI Standard 275 provides a procedure for converting the published ARI Sound Rating Level (SR) number which is a tonemected, A-weighted sound power level (determined in amdance with ARI 270) into a tone corrected, A-weighted sound pressure level for a specfic Wation. This procedure ac
12、counts for major acoustical barriers. Several alternate locations can be evaluated for the impact of wund on neighbors before actual installation of the equipment results in a problem. If there appears to be a problem during the planning stage, then the options scill include choosing an aitemate loc
13、ation, a quieter air conditioning uni and/or the application of severai methods of noise control. - factors such as distance, reflecting walls, and wund - Mdcipal piannm can use the ARI Directory and ARI 275 to help establish reasonable property line noise ordinances and perhaps recommend minimum lo
14、t size* or set back distances to help minimize the impact of equipment wund levels. * See section on Preplaming 4 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,- STD.ARI G
15、UIDELINE L-ENGL 1,997 = 0352320 OULLL, vLi m AR1 GUIDELINE L-1997 Curve No. 1 = 30.5 &(A) Curve No. 2 = 35.5 &(A) Curve No. 3 = 40.5 &(A) Curve No. 4 = 45.5 dE%(A) Curve No. 5 = 50.5 &(A) Curve No. 6 = 55.5 &(A) Curve No. 7 = 60.5 &(A) Figure 2. Estimated Outdoor Background Sound Pressure Levels as
16、a Function of Community Area HIGH ma E s 8 M pi O O u LOW I l I LOW SOUND PRESSURE LEVEL HIGH Figure 3. Cost Trend as a Function of Required Sound Pressure Level 5 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking
17、 permitted without license from IHS-,-,-STD-AR1 GUIDELINE L-ENGL 1777 0352120 0011L32 120 AR1 GUIDELINE L-1997 The use of ARI Standard 275 is perhaps best illusmated through the following example: Examule Figure 4 shows an outdoor unit located 5 ft. 1.5 m from the side of a house, and 15 A. 4.6 m ba
18、ck from the property line. There are no barriers and there is one reflective surface. The air conditioner sound levels will be estimated for three locations. These locations represent a backyard patio 47 ft. f14.3 m away, the property line 15 ft. t4.6 m away, and just inside an open window 35 ft. 10
19、.7 m away. The Sound Rating Level for the unit in this example is 80 dB. The calculations are shown in Table 2 as follows: 1. 2. 3. 4. 5. 6. Start with the equipment sound power rating. Add 3 dB Equipment Location Factor from Table 1, Item 1 of ARI 275 to account for the sound energy reflected back
20、from the wall next to the unit. Add zero for the Barrier Shielding Factor from Table 1, item 2 of ARI 275 since there is no acoustical barrier in this example. Add zero, zero, and 10 dB respectively for the Three points, for the Sound Path Factor of Table 1, item 3 in ARI 275 since there are two cle
21、ar sound paths and one open window. If the window were closed the Sound Path Factor would be 17 dB instead of 10 dB. Add the Distance Factor from Table 2 of A 275 forthethreedinereaitdistances:31dB,21dB,and 28 dB for distances of 47, 15, and 35 ft. 14.3,4.6 and 10.7 m respectively. This converts sou
22、nd power to sound pressure for each distance. Combine all of the levels and factors to obtain the estimated A-weighted sound pressure levels at the three evaluation points : 52 dB, 62 dB and 45 dB. The AFU 275 application standard also gives detailed examples of other installations that involve most
23、 typical application factors that are likely to be encountered. Section 8. Preplanning 8.1 Once the aforementioned procedures are understood, it is a rather straight forward extension to use ARI 275 to back-calculate acceptable lot sizes based on an existing community sound ordinance or to develop/m
24、odify a practical community sound ordinance based on existing available equipment sound levels. For example, consider evaiuation point #2 from the preceding example. If the community sound ardinance specified a level not to exceed 65 dB(A) at the property line, a unit with an ARI Sound Rating Level
25、of 80 dB would be acceptable. However, if the ARI guide indicates that typical sound rating levels for the type of equipment to be instailed averages 86 dB, the target sound level would not be achieved. In this situation, possible solutions include: 1. Increasing lot sizes such that the distance fac
26、tor provides sufficient attenuation to achieve the desired sound level. 2. Modifjing the sound orbance to recognize the fact that practical limitations on lot size and equipment design will not permit the original goal to be met. 3. Selecting quieter equipment which typically is more expensive. 4. T
27、reating the equipment on-site to achieve the desired sound level. This generally requires the expertise of an acoustical consultant. Although ARI Standards 270 and 275 do not specifically reammend a piece of equipment or equipment location to achieve a specied sound level, they do provide the inform
28、ation needed to make an intelligent, informed decision on selection of equipment. Preplanning is also important when drafting a building code to prevent unit placement in an offending area. Far example, the building code could state that the outdoor unit cannot be placed within 15 ft. 4.6 m of a nei
29、ghbors bedroom window. This alerts the builder of a subdivision that the houses must be designed with this in mind. Also, this resiction in the code would be hown by installing contractors in the area so that add on instaliations would also meet the code. Section 9. Corrective Measures (OnSite) 9.1
30、As previously mentioned, once the equipment is installed, the number of options available to achieve a specied sound level become limited and should involve the services of an acoustical consultant. Perhaps the most typical form of corrective action involves a total or partial sound enclosure or bar
31、rier. These devices are generally constructed such that they absorb, block, or redirect the sound or some combmtion of the three. It is extremely important that the use of such devices not alter the norrnal operation of the equipment being treated. It is also very important that a thorough understan
32、ding of the problem be reached before a design is selected. Relatively rninor mistakes in a design can result in only a fraction of the estimated attenuation being achieved. - - . 6 Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduc
33、tion or networking permitted without license from IHS-,-,-STD-AR1 GUIDELINE L-ENGL 1777 Another type of corrective action is modincation of the dwelling. Single pane windows can be replaced with dual or triple pane windows. Also, storm windows or storm doors could be adde for a degree of sound reduc
34、tion. In an extreme case, a masonry wall could be added to the side of a dwelling for a noise barrier. Before any corrective meames are taken, however, an acoustical consultant should analyze the situation. A consultant could analyze the existing situation and recommend the appropriate corrective ac
35、tion. For example, he may recommend possible modification of windows, doors, or wails that would give a greater iransmission loss depending on the nature of the offending noise. Section 10. Special Considerations 10.1 There are some types of housing which can pose signincant problems when trying to
36、establish a reasonable outdoor sound ordinance. Typically, these types of housing are of higher density than the normal residential community. For example, a town-house may be in an urban setting where the houses are built very close to property lines. An air-conditioning unit on the side of a house
37、 may be only 6 fi. 1.8 m away from a neighbors window and even with a low sound rating level, could easily exceed a property line sound level based on more typical residential community lot sizes. A property line sound level for town homes might not be sufficient to avoid complaints. In these situat
38、ions, a change to the building code might be necessary to prevent unit placement in an area which would be particularly offensive to a neighbor. 0352320 OOLlL33 Ob7 AR1 GUIDELINE L-1997 Low rise apartment buildings can also pose difficult problems. Two and three story apartment buildings can have in
39、dividual air conditioning units for each apartment. As a possible solution in Southern areas, these apartment buildings can be built with a flat roof, and ail outdoor units can be placed on the roof and away from neighbors. in other areas, the outdm unit must be placed on the ground. In this situati
40、on, it must be remembered that a large number of units clustered together can generate noise complaints even if each individual unit has a low sound rating level. These two types of housing or other high density situations are extremely complex and it is recommended that the services of an acoustica
41、l consultant be considered before guidelines are drawn up for a community. action 11. Determination of Compliance 11.1 As with any type of ordinance or specification, there must be a means of detemWiing compliance. When dealing with sound, compliance is generally determined through on-site measureme
42、nts made with a hand held sound level meter. Recommended meters fall into two types, each with its own measurement tolerance, or accuracy. Within each type, meters exist which provide the user with either overall dB(A) sound levels, octave band sound levels, or one-third octave band sound levels. Th
43、e sound level meter is selected such that it provides the accuracy needed and the data needed in the format specified in the ordinance. More information on sound level meters can be obtained in ANSI Standard S 1.4 . The highest level of accuracy is attained with the Type 1 meter which is termed a “p
44、recision instrument.“ Type 2 is for general purpose measurements. Table 3 illustrates the tolerances allowed for the “A“ scale weighting on two instrument types. Sound Rating of Unit = 80.0 B(A) Figure 4. Example of Installation With No Barrier and One Reflective Surface 7 Copyright Air-Conditioning
45、 and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-STD-AR1 GUIDELINE L-ENGL 1777 0352320 OnLL13q TT3 Line 1 2 AR1 GUIDELINE L-1997 Distance from Equipment to Evaluation Point UnitSoundRating bel Equipn
46、mtLdon Factor (Table 1, Itan 1, Ai 275) Table 2. Sample Calculations for Example from AR1 Standard 275 nts 3 4 5 6 7 8 Evaluation P 7 AddLinesland2 83 83 83 BanierShielding O O O Fador (Tabie 1, Item 2, Ai 275) SoundPathFactor O O 10 (Table 1, Item 3. ARi 275) DistanFactor 31 21 28 (Table 2. Ai 275)
47、 AddLines4.5and6 31 21 38 EhatedA- 52 62 45 Weighted Sound RessureL.evel (35dB) subtrad Line 7 from Line 3 47ft I 15ft L14.3 ml 4.6 ml 63 125 250 500 1000 2000 4000 1 8000 I f 1.0 i 1.0 f 1.0 f 1.0 fl.0 f 1.0 i f 1.0 1 f 1.5 - 3.0 -t 3 35% 10.7 m 80 3 Table 3. Tolerance, A-Weighted dB Frequency f 3.
48、0 f 2.5 f 2.5 f 2.0 f 2.0 f 3.0 f 5.5 - 4.5 f 6.5 As a guide, the following steps have been identified as being necessary fa the collection of accurate, on-site sound data: a. b. C. d. Skerch. Make a sketch of the measurement area showing measurement locations, unit orientation and distance to measu
49、rement points, lot lines, walls, etc. Calibrution of Instrumentation. This is done by using an acoustic calibratar, usually a pistonphone, as a scum of known sound pressure and adjusting the meter to indicate that level. Determination of Background Level. Measure background level without unit operating. This background level must be at least 6 dB below unit operating level or data will be considered invalid due to background connibu
