1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2017 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/J2846_201708 SURFACE VEHICLE RECOMMENDED PRACTICE J2846 AUG2017 Issued 2010-05 Reaffirmed 2017-
5、08 Superseding J2846 MAY2010 Laboratory Measurement of the Acoustical Performance of Body Cavity Filler Materials RATIONALE SAE J2846 has been reaffirmed to comply with the SAE Five-Year Review policy. 1. SCOPE This SAE Recommended Practice describes a laboratory test procedure for measuring the aco
6、ustical performance of a system consisting of a body cavity filler material formed into a rectangular cross-section channel. Materials for this test may include both heat reactive and chemically reactive products, with or without a shelf to simulate a baffle in an application, or a combination of bo
7、dy cavity filler and aluminum foil to enhance the performance. These materials are commonly installed in transportation systems such as ground vehicles, and thus reduce the noise propagation through the rails, rockers, and pillar/posts. This document is intended to rank order the acoustical performa
8、nce of materials for application on channels using general automotive steel, such that the effects of sealing of pinch welds in addition to the material could be easily evaluated. However, the channel is not an actual part (i.e., real life section) of the vehicle, and therefore results obtained from
9、 this study will have to be carefully interpreted considering limitations of section size/shape and full sealing (or not) of the section. The acoustical performance is expressed in terms of insertion loss (IL) which is described in Section 3 Test Method. The test procedure described here is based on
10、 the method described in SAE J1400. However, this document differs from the SAE J1400 method in that the J1400 measures sound transmission loss, and this document measures IL of body cavity materials in a cavity. This document covers the useful frequency range of interest in 1/3 octave band center f
11、requencies. The lower limit of the actual frequency range is limited by the size of the channel and/or the volume of the reverberation room. Two rectangular cross-section channels are cited in this standard. These are 75 mm x 75 mm and 150 mm x 150 mm in cross-section and provide valid data at and a
12、bove 800 Hz and 400 Hz 1/3 octave band frequencies, respectively, provided the reverberation room can generate diffuse sound field at those frequencies. 2. REFERENCES2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise
13、 indicated, the latest issue of SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. SAE TSB 003 Rules for SAE Use of SI (Metric)
14、 Units SAE J184 Qualifying a Sound Data Acquisition System SAE J1400 Laboratory Measurement of the Airborne Sound Barrier Performance of Automotive Materials and Assemblies 2.1.2 ANSI PUBLICATIONS Available from American National Standards Institute, 25 West 43rdStreet, New York, NY 10036-8002, Tel:
15、 212-642-4900, www.ansi.org. ANSI S 1.1 Acoustical Terminology ANSI S 1.4 Specifications for Sound Level Meters ANSI S1.40 Specifications for Acoustical Calibrators ANSI S 1.11 Specification for Octave Band and Fractional Octave Band Filter Sets 3. TEST METHODThe method is based on evaluating the pe
16、rformance in terms of Insertion Loss (IL). The term, IL in this case is the difference in sound pressure levels at a receiving location resulting from insertion of the sound insulating structure in a hollow cavity (channel) (Figure 1). The sound insulating structure in this case is the body cavity f
17、iller material. The concept of IL measurement assumes that the sound pressure level produced by the source is the same for both the “Before“ and “After“ test conditions. Both unfilled (bare) and filled channels need to be tested. The IL performance is expressed as: IL = SPL1 SPL2(Eq. 1)where: SPL =
18、Sound pressure level, dB SAE INTERNATIONAL J2846 AUG2017 2 OF 10SPL1BeforeSOURCEAfterSOURCESPL2Unfilled channelFilled channelFIGURE 1 - INSERTION LOSS SCHEMATIC 4. INSTRUMENTATIONThe instrumentation to be used is as follows: 4.1 A microphone, measuring amplifier, and a sound data acquisition system
19、which meets the requirements of SAE J184, or a sound level meter meeting Type I requirements of ANSI S 1.4 shall be used. 4.2 A one-third-octave band filter set covering the range of center frequencies from 100 to 10 000 Hz; the filters shall meet the Class III requirements of ANSI S 1.11. 4.3 A sou
20、nd level calibrator that meets the Class 1 requirements of ANSI 1.40 and is accurate to 0.5 dB. 4.4 An acoustical sound generating system shall be selected to generate random noise containing a continuous distribution of frequencies over the range of interest. 4.5 A schematic diagram of the instrume
21、ntation is shown in Figure 2. FIGURE 2 - TYPICAL MEASUREMENT SYSTEM Random Noise Generator Spectrum Shaper Power Amplifier Speaker Computer Spectrum Analyzer Amplifier Typical Noise Generation SystemTypical Data Acquisition SystemStationary Single Microphones, Spatially-averaged Single Microphones o
22、r Averaged Multi-point Microphones Receiving Room Microphone Source Room Microphone SAE INTERNATIONAL J2846 AUG2017 3 OF 105. TEST FACILITYThe facility needed for this study is generally the same as that for the sound transmission loss test as discussed in the SAE J1400 test procedure. This includes
23、 a reverberation room that is used as the source room and an anechoic, a hemi-anechoic, or a quiet room that is used as the receiving room with a test window in between to mount the channel. The test window is typically vertical. It is recommended that the receiving room be anechoic in order to mini
24、mize the influence of flanking paths and modal coupling between the two rooms. Refer to the SAE J1400 standard for the details of the room including criteria to eliminate flanking paths. A schematic diagram of a typical measurement facility is shown in Figure 3. FIGURE 3 - A SCHEMATIC OF THE TYPICAL
25、 TEST FACILITY 6. TEST SET-UP/METHODThe test set-up to be used is as follows: 6.1 The size of the channel and the environment of the test chamber is critical to the test results. The rockers, pillars, and posts in an application are all different. It is recommended to use rectangular cross-sectional
26、 channels with pinch welds for simplicity but still to provide some simulation of actual applications. The most common test channel to be used is of 75 mm x 75 mm in cross-section and 250 mm in length. However, in many applications, such as the sail panel, or D-Pillar, larger size channels may be re
27、quired. Therefore, for such applications, a channel of 150 mm x 150 mm in cross-section and 250 mm in length should be used. The most common material for constructing the channels is 0.8 mm thick (20 gauge thick) cold rolled steel. Figure 4 shows an orthographic schematic of the channel, including m
28、ounting attachments (straps) to mount to a fixture. Source roomReceiving Room SAE INTERNATIONAL J2846 AUG2017 4 OF 10FIGURE 4 - ORTHOGRAPHIC SCHEMATIC OF THE CHANNEL 6.2 The largest size of the opening of the channel (i.e., the diagonal) based on one-quarter of the wavelength of sound, establishes t
29、he low frequency limit below which measurements cannot be made reliably (Table 1 in SAE J1400 standard). Above this frequency, sound will propagate freely through the opening. The 75 mm x 75 mm cross-section channel has a useful frequency range starting from 800 Hz 1/3 octave band frequency and up b
30、ased on the diagonal of the opening of the channel. At frequencies lower than 800 Hz, the results are affected by the fundamental resonance of the channel and although the results may still be useful, the reliability may be questionable, and therefore, it is recommended to use results above the usef
31、ul frequency. The useful low frequency of the 150 mm x 150 mm channel, based on the diagonal of the opening of the channel, is 400 Hz 1/3 octave band frequency. 6.3 The channel is generally mounted on a plate that is placed in the opening between the source room and the receiving room. The channel c
32、an be extended toward the source room or the receiving room. Figures 5 and 6 show schematics of the channel extended toward the source room and toward the receiving room, respectively. SAE INTERNATIONAL J2846 AUG2017 5 OF 10Extreme care needs to be taken when the channel extends in to the source roo
33、m so that sound incident only on the opening of the channel is considered for the measurement. Likewise, care needs to be taken so that sound does not flank through the plate for a channel extended toward the receiving room. In order to ensure this, for a channel extended toward the source room, a s
34、pecial test fixture may have to be constructed (the plate to which the channel is mounted, could be used as part of the fixture) such that the anticipated insertion loss of the highest performing test channel is at least 10 dB greater than that of the same channel without any special test fixture. T
35、he fixture could be a massive box with a removable plate toward the source room and a fixed plate toward the receiving room as shown in Figure 5. The fixture walls need to have a minimum acoustical performance of equivalent to a homogeneous barrier of 40 kg/m2. Any open space inside the fixture shou
36、ld be filled with absorption materials to improve the effective acoustical performance of the fixture. For a channel extended toward the receiving room, the plate to which the channel is mounted also needs to have a performance comparable to that of a 40 kg/m2single layer barrier (Figure 6). In both
37、 cases the plates need to have openings at the center, of the cross-sectional area large enough such that the channel will be flush with the plate facing the source room. The channel should be sealed within the plate with ancillary shielding or seals to help ensure a minimum of sound flanking the te
38、st sample (Figure 7). FIGURE 5 - SCHEMATIC OF THE TEST SET-UP WHERE THE CHANNEL IS EXTENDED TOWARD THE SOURCE ROOM Channel Wall separating the source room and receiving room, Filler Material Plate facing the reverberation room (source room) Fixture to hold the Channel Back plate (could be a part of
39、the fixture), mounted to the channel and placed in the opening between the source and receiving rooms Acoustical performance equivalent to at least 40 kg/m2barrier SAE INTERNATIONAL J2846 AUG2017 6 OF 10FIGURE 6 - SCHEMATIC OF THE TEST SET-UP WHERE THE CHANNEL IS EXTENDED TOWARD THE RECEIVING ROOM F
40、igure 5 FIGURE 7 - ILLUSTRATION OF SEALING ON THE FRONT PLATE TO MINIMIZE SOUND FLANKING 6.4 The test samples should be prepared in such a way that the filler material is flush as much as possible at one end of the channel and this end of the channel should face the receiving room. It should be note
41、d that although the material is made to be flush to one end of the channel (this can be attained by using a plate or some other constraining surface that can be either left there should the application require, e.g., a carrier, or removed after the sample is prepared), it is made to expand toward th
42、e other end freely. 6.5 The receiving room microphone should be 100 mm away from the end of the channel at the centerline of the channel longitudinal axis, facing the test sample (this is also the vertical plane where the filler material is flush to the end of the channel) (Figure 8). Front Plate Se
43、aling Material Test Channel Plate to which the channel is mounted Channel extended toward receiving room Acoustical performance equivalent to at least 40 kg/m2barrier SAE INTERNATIONAL J2846 AUG2017 7 OF 10THE RECEIVING ROOMSourceRoomSample (Filler)ChannelReceivingRoom100 mmNMicrophoneMicrophoneFLUS
44、H END OF SAMPLE SHOULD FACEFlush end of the sample should face the receiving roomFIGURE 8 - SCHEMATIC OF THE TEST SET-UP (THIS FIGURE SHOWS THAT THE CHANNEL IS EXTENDED TOWARD THE SOURCE ROOM) 7. PROCEDURE7.1 Sample Conditioning Although it is not required, it is encouraged to condition the test sam
45、ples for at least 12 hours at the same temperature and humidity as the test rooms. The source and receiving room temperatures should be controlled to 22 C 5 C. Relative humidity should be controlled for both chambers at 40 to 70%. 7.2 Measurements Background noise levels within both the source and r
46、eceiving rooms shall be measured and noted in all measurement bands. It is recommended that the source signal be filtered or shaped so that with the test sample sealed in place, the source room and receiving room signal levels are each at least 15 dB higher than the background noise levels in the re
47、spective rooms for the same gain settings and within the dynamic range capability of the measurement system at all 1/3 octave band frequencies of interest. 7.2.1 Install the unfilled (bare) channel in the test fixture. 7.2.2 The time and space averaged one-third octave band sound pressure level in t
48、he source room and the corresponding sound pressure level at a single microphone location in the receiving room shall be measured and recorded over the desired measurement frequency range with the bare channel sealed into the fixture in the test opening. The total averaging time of the sound level d
49、ata acquired shall be at least 30 seconds. 7.2.3 After removing the bare channel, the test channel with the body cavity filler material in place (i.e., the filled channel) is installed and sealed into the same opening and the measurements of 7.2.2 are repeated. SAE INTERNATIONAL J2846 AUG2017 8 OF 108. DATA ANALYSISThe following procedures are used to compute the IL of the body cavity filler material at each test frequency: 8.
