1、 2008 Standard for Procedure for Estimating Occupied Space Sound Levels in the Application of Air Terminals and Air Outlets AHRI Standard 885 with Addendum 1 (formerly ARI Standard 885) AHRI STANDARD 885-2008 WITH ADDENDUM 1, PROCEDURE FOR ESTIMATING OCCUPIED SPACE SOUND LEVELS IN THE APPLICATION OF
2、 AIR TERMINALS AND AIR OUTLETS March 2011 Addendum 1 (dated March 2011) of AHRI Standard 885-2008, Procedure for Estimating Occupied Space Sound Levels in the Application of Air Terminals and Air Outlets, is provided as follows. The particular additions are shown with shading and the deletions shown
3、 with strikethroughs. Table 8. Step-By-Step Calculation for the Procedural Example of Figure 6 SOUND PATH Octave Band Mid Frequency, Hz PATH # NAME 125 250 500 1000 2000 4000 Radiated and Induction Inlet Radiated and induction inlet Lw (from mfrs data, Table 5) 64 60 57 58 55 52 Environmental Adjust
4、ment Factor (6.2) -2 -1 0 0 0 0 Ceiling/Space Effect, Table D14, Type 1 Ceiling -16 -18 -20 -26 -31 -36 Radiated path Lp at receiver location 46 41 37 32 24 16 Duct Breakout Transmission Loss Path Terminal discharge Lw (from mfrs data, Table 5) 66 65 62 62 62 60 Environmental Adjustment Factor (6.2)
5、 -2 -1 0 0 0 0 5.0 ft 1.5 m lined rectangular duct 12 in x 12 in 300 mm x 300 mm, 1.0 in 25 mm FG (D1.3.2) (See Note 1) -1 -4 -10 -22 -20 -9 Duct transmission loss breakout noise, 0.03 in 0.7 mm (D1.2.4) -24 7 -27 10 -30 13 -33 16 -36 19 -41 24 Ceiling/Space Effect, Table D14, Type 1 Ceiling -16 -18
6、 -20 -26 -31 -36 Duct breakout transmission loss path Lp at receiver location 23 40 15 32 2 19 * * * Distribution Duct BreakoutTransmission loss Path Terminal discharge Lw (from mfrs data, Table 5) 66 65 62 62 62 60 Environmental Adjustment Factor (6.2) -2 -1 0 0 0 0 10 ft 3 m lined rectangular duct
7、 12 in x 12 in 300 mm x 300 mm, 1.0 in 25 mm FG (D1.3.2) (see Note 2) -2 -6 -16 -40 -40 -25 Rectangular Tee attenuation entering branch duct (D1.4.4) 0 0 -1 -5 -7 -5 Branch power division 50% split (D1.1) -3 -3 -3 -3 -3 -3 5.0 ft 1.5 m unlined rectangular duct (D1.3) 0 0 0 0 0 0 E D1 I1 D1 P C1 E E
8、P B T F I2 I1 Table 8. Step-By-Step Calculation for the Procedural Example of Figure 6 (continued) SOUND PATH Octave Band Mid Frequency, Hz PATH # NAME 125 250 500 1000 2000 4000 Duct breakout noise transmission loss, 0.03 in 0.7 mm (D1.2.4) (12 ft in x 12 ft in 300 mm x 300 mm, 10 ft 3 m long) -2 4
9、 -27 7 -30 10 -33 13 -36 16 -41 21 Ceiling/Space Effect, (D1.6) Table D14, Type 1 Ceiling -16 -18 -20 -26 -31 -36 Distribution duct breakout transmission loss Lp at receiver location 19 39 10 30 12 * * * Flexible Duct Breakout Transmission Loss Path Terminal discharge Lw (from mfrs data, Table 5) 66
10、 65 62 62 62 60 Environmental Adjustment Factor (6.2) -2 -1 0 0 0 0 10 ft 3 m lined rectangular duct 12 in x 12 in 300 mm x 300 mm, 1.0 in 25 mm fiberglass D1.3.2 (see Note 2). -2 -6 -16 -40 -40 -5 Rectangular Tee attenuation entering branch duct (D1.4.4) 0 0 -1 -5 -7 -5 Branch Power Division, 50% s
11、plit, D1.1 -3 -3 -3 -3 -3 -3 5.0 ft 1.5 m unlined rectangular duct (D1.3) 0 0 0 0 0 0 3.0 ft 0.9 m lined 8 in 200 mm diameter non-metallic flexible duct (D1.3.3) -4 -7 -14 -15 -16 -8 Duct transmission loss, 8 in 200 mm diameter non-metallic flexible duct (D1.2.2) -8 -8 -8 -9 -10 -13 Ceiling/Space Ef
12、fect, Table D14, Type 1 Ceiling. -16 -18 -20 -26 -31 -36 Flexible duct breakout transmission loss path Lp at receiver location 31 22 0 * * * Discharge Path Terminal discharge Lw (from mfrs data, Table 5) 66 65 62 62 62 60 Environmental Adjustment Factor (6.2) -2 -1 0 0 0 0 10 ft 3 m lined rectangula
13、r duct, 12 in x 12 in 300 mm x 300 mm, 1.0 in 25 mm fiberglass (D1.3.2) (see Note 2) -2 -6 -16 -40 -40 -5 Rectangular Tee attenuation entering branch duct (D1.4.4) 0 0 -1 -5 -7 -5 Branch Power Division , 50% split (D1.1) -3 -3 -3 -3 -3 -3 5.0 ft 1.5 m unlined rectangular duct (D1.3)0 0 0 0 0 0 D1 T
14、F I2 I3 B P I1 B P E I1 E D1 T F I2 Table 8. Step-By-Step Calculation for the Procedural Example of Figure 6 (continued) SOUND PATH Octave Band Mid Frequency, Hz PATH # NAME 125 250 500 1000 2000 4000 5.0 ft 1.5 m lined, 8 in 200 mm diameter non-metallic flexible duct (D1.3.3) -5 -10 -18 -19 -21 -12
15、 End reflection Factor, 8.0 in 200 mm diameter (D1.5) -10 -5 -2 -1 0 0 Space Effect (5.0 ft 1.5 m, 2400 cu ft 67 m3 room, Table D15) -5 -6 -7 -8 -9 -10 Discharge Lp at receiver location 39 34 15 * * 25 Outlet #1 Generated Outlet generated Lw (from mfrs data, Table 5) 40 43 46 46 44 42 Environmental
16、Adjustment Factor (6.2) -2 -1 0 0 0 0 Space Effect (5.0 ft 1.5 m, 2400 cu ft 67 m3 room, Table D15) -5 -6 -7 -8 -9 -10 Outlet generated Lp at receiver location 33 36 39 38 35 32 * Less than zero dB Note 1: For lined duct lengths up to 15 ft 4.5 m, take duct insertion loss before calculating breakout
17、 transmission loss (max. 7.5 ft 2.3 m) Note 2: The maximum recommended lined duct attenuation in any octave band is 40 dB. See D1.3.2. The contributions of the six individual paths as shown on the acoustic model will be combined to obtain the total Sound Pressure Level, Lp at the receiver location.
18、A similar calculation may be completed for various receiver locations (i.e., directly under the terminal or directly under the diffuser) in order to determine the acoustically critical receiver location. The paths considered are: 1. Radiated and induction inlet 2. Duct Transmission Loss Breakout 3.
19、Distribution Duct Transmission Loss Breakout 4. Flexible Duct Transmission Loss Breakout 5. Discharge 6. Outlet #1 Generated O1 I3 R S S E Table 9. Summary Combination of Path Results Using Logarithmic Addition, dB Path # Description Octave Band Mid Frequency, Hz 125 250 500 1000 2000 4000 Radiated
20、and induction inlet path 46 41 37 32 24 16 Duct breakout transmission loss path 23 40 15 32 2 19 * * * Distribution duct breakout transmission loss path 19 39 10 30 0 12 * * * Flexible duct breakout transmission loss path 31 22 0 * * * Discharge path 39 34 15 * * 26 25 Outlet #1 generated path 33 36
21、 39 38 35 32 Total Lp at receiver location check numbers here 47 48 43 41 39 35 33 * less than zero dB Note: In this example it can be seen that the critical paths are casing radiated (Path #1), discharge (Path #5) and outlet generated (Path #6). 6.6 Additional Acoustic Models. Examples of the acous
22、tic paths involved with single/dual duct terminal boxes and integral diffuser terminals are illustrated in Figures 7 and 8. The associated path factor calculations are tabulated in the summary calculation Tables 10 and 11 which list the source of the attenuation data. Figure D1. Branch Power Divisio
23、n A1 A3 A2 A1 A2 A3 Table D2. Power Level Division at Branch Takeoffs B/T Division, dB B/T Division, dB 1.00 0.80 0.63 0.50 0.40 0.32 0.25 0.20 0.16 0.12 0 1 2 3 4 5 6 7 8 9 0.100 0.080 0.063 0.050 0.040 0.032 0.025 0.020 0.016 0.012 10 11 12 13 14 15 16 17 18 19 Reprinted with permission of the Ame
24、rican Society of Heating, Refrigerating the transmission loss is dependent on the duct geometry. D1.2.1 Circular Sheet Metal Duct. is calculated from the transmission loss characteristics of the duct and from the cross sectional typically, the Sound Power obtained from manufacturers sound power data
25、 determined in accordance with ASHRAE Standard 70 and ASHRAE Standard 130. , and are calculated as follows: = - = - = - where is the Environmental Adjustment Factor E E O1 O E D1 D E C1 C O D C O1 O D1 D D C1 C C AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-2008) 5 = Environmental Adjustment Fa
26、ctor. The Environmental Adjustment Factor is required in order to use the calculation procedures defined herein (refer to Appendix C). Sound power measurement for Air Terminals is defined in AHRI Standard 880. Real rooms at low frequencies are highly reverberant which causes the source to radiate le
27、ss low frequency noise than if the source were operating in a free field (outdoors). For this reason, it is necessary to adjust manufacturers sound power data before applying the data to estimate Sound Pressure in occupied spaces. Differential values between the two sources have been determined and
28、must be subtracted from manufacturers data as a part of the calculation. The values are shown in Table 2. Table 2. Environmental Adjustment Factor Octave Band Center Frequency, Hz Environmental Adjustment Factor, dB 63 4 125 2 250 1 500 0 1000 0 2000 0 4000 0 8000 0 Note: This reflects the results o
29、f ASHRAE RP755, Sound Transmission through Ceilings from Air Terminal Devices in the Plenum. A more detailed explanation of the environmental adjustment factor is found in Appendix C. 4.2 Sound Path. = Duct Breakout Transmission Loss, Lined or Unlined. Difference between Octave Band Sound Power Leve
30、l entering a duct section and the Sound Power radiated by the section of duct. = Flow Division Noise Reduction. Reduction in octave band Sound Power Level along a path, attributable to the division of air flow. = Duct Insertion Loss. Difference between the octave band airborne Sound Power entering a
31、 duct section and the airborne Sound Power leaving the duct section. = Manufacturers Attenuation Element. Difference between the airborne octave band Sound Power Level entering the manufacturers attenuation element and the Sound Power leaving the element. = Ceiling/Space Effect. Difference between t
32、he octave band Sound Power Level from the source located in the plenum/ceiling cavity and the Sound Pressure received in the occupied space. = Duct End Reflection Loss. The sudden area change at the exit of an integral terminal unit or outlet can reflect significant low frequency energy back into th
33、e attached ductwork. The end reflection loss accounts for this. It is the difference between the octave band Sound Power incident on a duct end and the Sound Power transmitted out of the end of a duct. E AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-2008) 6 = Space Effect. Difference between the
34、 octave band Sound Power Level entering the occupied space and the resulting octave band Sound Pressure Level at a specific point in an occupied space. = Lw - Lp where: Lw = Sound Power Level Lp = Sound Pressure Level = Duct Elbow and Tee Loss. Difference between the airborne octave band Sound Power
35、 Level entering a lined or unlined elbow or tee duct connection and the airborne Sound Power leaving the elbow or tee when the elbow or tee is coupled with at least three duct diameters of lined duct upstream and/or downstream of the elbow or tee. 4.3 Receiver Symbols and Definitions. = Resultant So
36、und Pressure Level at the receiver calculated along Path 1. = Resultant Sound Pressure Level at the receiver calculated along Path 2. = Resultant Sound Pressure Level at the receiver calculated along Path N. = Resultant logarithmic sum of Sound Pressure Levels at the receiver from all sound paths fo
37、r a specific Octave Band. Section 5. Description of Sound Estimating Method 5.1 Introduction. The sound estimating method used in this standard is based on a simple process called Source-Path-Receiver. A given Source of sound travels over a given Path to an occupied space where a Receiver hears the
38、sound produced by the Source as in Table 3. 5.2 Outline of the Sound Pressure Estimating Procedure. This standard estimates space Sound Pressure Levels when the acoustic performance of Air Terminals and/or outlets is known. A second use of the standard is to estimate the maximum permissible Sound Po
39、wer Level from a terminal device so that a selected acoustical design criteria (NC or RC) will not be exceeded. Four steps are required to estimate Sound Pressure Levels by Octave Band: 5.2.1 Obtain Air Terminal or outlet Sound Power Levels at the specific unit operating point(s). Source: Manufactur
40、ers Data. 5.2.2 Identify the sound paths to be evaluated. Source: Acoustic Model. 5.2.3 Determine the attenuation path factors for each path. Source: Appendix D, Standard 885. 5.2.4 Logarithmically add the acoustic contribution from each sound path to determine overall Sound Pressure Level. 5.3 Acou
41、stical Models. Acoustical models for each of the major Air Terminal/distribution applications are shown in Figures 1, 2 and 3 which follow. The models identify receiver sound paths and graphically illustrate the process of sound level prediction. Lp AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-
42、2008) 7 5.4 Upstream Sound Sources. This standard does not take into consideration sound breaking out of the inlet ducts to Air Terminal devices as shown (by the dashed-line arrow) in the upstream duct breakout radiated path in Figure 1. Sound emitted from this element can come from these sources: 1
43、. The airborne sound from the system central fan; 2. Airborne regenerated sound from upstream takeoffs and fittings; 3. Sound traveling upstream from the terminal. At the present time, catalog data is not available for sound traveling upstream from the Air Terminal. It is difficult to estimate becau
44、se of the wide variety of fittings used. If the designer feels upstream noise might be significant (e.g., where a terminal is mounted close to the supply fan), it is recommended that hard duct be used or that flex duct be lagged. Table 3. Source Path Receiver Process Process Description Air Terminal
45、s and outlets are examples of sound Sources. The sound travels over one or more Paths where attenuation takes place. A person in the occupied spaces who hears the sound at the receiver location. Symbols Used in this Standard A circle denotes a sound Source. The letter defines which Source. A triangl
46、e denotes an attenuation on the sound path. The letter defines the type of attenuation A square denotes a sound Receiver. The number defines the sound path being considered. Nature of Data Octave band Sound Power Level Octave band Path Attenuation Octave band Sound Pressure Level (Lw) of Source in d
47、ecibels (dB). Sound reduction due to ducting, ceiling tile, etc. (Lp) at receiver location. Often evaluated as Noise Criteria (NC) or Room Criteria (RC). Sources of Data Manufacturers data tested in accordance with: Air Terminals ASHRAE 130 Air outlets ASHRAE 70 AHRI Standard 885, Appendix D. Calcul
48、ated by procedures in AHRI Standard 885. C Source Path Receiver AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-2008) 8 Figure 1. Fan-Powered Terminal or Induction Terminal Acoustic Model AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-2008) 9 Figure 2. Single, Double Duct Terminal Acoustic Mode
49、l AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-2008) 10 Figure 3. Integral Diffuser Terminal Acoustic Model AHRI STANDARD 885-2008 (formerly ARI STANDARD 885-2008) 11 CorrectiontobeAddedtoHigher Value(dB)Difference in Decibels Between Two Values Being Added (dB) Section 6. Calculation Procedures for Estimating Sound Levels in Occupied Spaces 6.1 Introduction. Figures 5, 6 and 7 display the source paths which must be evaluated to enable the net sound level in a conditioned space to b
