1、FORD LABORATORY TEST METHOD BV 003-05 SOUND ABSORPTION TEST Date 2001 10 31 2000 08 11 1992 08 11 Application The objective of this test is to evaluate the sound absorption qualities of materials. Action Revisions Revised Editorial - no technical change A. Cockman Revised Editorial - no technical ch
2、ange A. Cockman Apparatus Required 1. Sound Absorption Tunnel. (a) The sound absorption tunnel walls are made of 3/4 inch plywood and the interior is lined with 1/32 inch aluminum. The aluminum plywood laminate is secured by means of screws. The two materials are on all six sides of the tunnel. (b)
3、The sound source consists of six 6 x 9 inch automotive-type loud-speakers. (c) The loudspeakers are mounted in a baffle box having interior dimensions of 24 x 24 x 10 1/2 inches. The loudspeaker openings are 6 inches in diameter. The interior of the baffle box has randomly arrayed 1/2 inch fiberglas
4、s behind the loudspeakers. (d) The absorption material lays flat on the bottom of the tunnel. The two pieces of material used on the sides are held up with masking tape. If the pieces used on the side are warped and will not stand flat against the sides additional tape should be used to make it stay
5、 against the side. (e) The interior dimensions of the absorption tunnel (excluding loud-speaker baffle area) are 24 x 24 x 72 inches. 2. Type WE 630A Western Electric microphone, or equivalent. 3. Ford Motor Wobulated Oscillator with center frequencies of 500, 1000, 2000, 3000, 4000, 5000 Hz, with a
6、 10 % deviation above and below the center frequency, occurring at the rate of 40 Hz, or equivalent. 4. Ballantine A.C. Voltmeter, Model 300-D, or equivalent. 5. Moseley X-Y Recorder, Model 2-D, or equivalent. Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 6. Log
7、 Voltmeter Converter, Model HLVGI 50, or equivalent. 7. Western Electric Acoustical Laboratories Microphone Preamplifier, Type 1 O0 D/E, or equivalent. 8. Fisher Amplifier, Model 50-A, or equivalent. (Refer to Page 7 for block diagram.) 9. Lasico Polar Planimeter No. 121 R, Serial No. 5789, or equi
8、valent. IO. Microphone Drive and “X“ Axis Control System Components: These components serve to drive the microphone from the speaker end of the tunnel to the opposite end and to return the microphone to its original position. They also provide a DC signal to the “X“ Axis of the recorder that coincid
9、es with the microphone travel. (a) Motor Type: Honeywell Part No. 362479-3 (no lead speed at 110 V, 60 Hz = 23 rpm) mounted on an aluminum plate which is attached to the end of the tunnel using resilient mounts as shown in photographs on Page 9. (b) Motor Control Box mounted to the end of the tunnel
10、 as shown on Page 9. (c) Remote Control Switch mounted on instrument console. (d) Four pulleys and micro switches as shown on Pages 5 and 9. (e) Microphone carriage, cables and miscellaneous hardware shown on Pages 3 and 9. (9 A 15 turn 1 O KS Helipot connected across a No. 6 Eveready (or equivalent
11、) 1 1/2 volt dry cell. The Helipot is coupled to the mcro-phone drive motor by two pulleys and a rubber drive belt (see Figure 1). The voltage from (see Figure 2) the center tap of the pot is used to control the Xaxis of the recorder. Refer to Page 7 for the circuit block diagram and Page 9 for phot
12、egraphs. Conditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 OC and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Page 2 of 1
13、2 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 1. 2. 3. 1. 2. 3. Test Preparation Cut three pieces of the material to be tested, 2 x 5 feet. Place the pieces on the two sides and the bottom of the sound absorption tunnel starting at the speaker end. Place the mi
14、crophone at the speaker end of the tunnel. Adjust the output of the Wobulated Audio Oscillator to indicate 100 db at 1000 Hz on the Log Voltmeter. Then adjust the “Y“ axis of the XY recorder to read 100 db on the sound absorption test chart. Adjust the “X“ axis of the recorder full scale to correspo
15、nd to the microphone travel. Test Method The test is to be performed at 500, 1000,2000, 3000,4000 and 5000 Hz. Set the Wobulated Audio Oscillator to the desired frequency. Simultaneously turn on the XY Recorder and the microphone drive system. When the microphone has been drawn to the end of the tun
16、nel opposite the speakers, stop the recorder, remove the chart and average the results as follows: (a) Measure the length of the chart in inches. (6 inches on the G.P.D. sound absorption test chart). (b) Measure the area under the curve with a Planimeter (square inches - Planimeter scale by K). “K“
17、set at .O1 5 for these tests. (c) Determine the average height above bottom line on chart and multiply by 10 to get db above 75. (Bottom line of chart is 75 db with pre-amplifier adjusted as described in Step 2 of Test Preparation. Chart covers 10 db per inch.) Average db = 75 +/- Scale x K x 10 Bas
18、e The difference between the average sound levels in the tunnel with and without the test material, at a given frequency, is the attenuation due to the sound absorption of the material being tested. Page 3 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 4. Fr
19、om a Standard Reference Decibel Table, find the decimal ratio corresponding to the db attenuation. Subtract the ratio from unity to obtain a decimal reduction. This reduction is the absorption coefficient of the material. Example: Attenuation - 1.5 db Decibel Table - Ratio - .84 Reduction - 1 .O - .
20、84 = .I6 absorption coefficient of 16 % absorption The overall absorption coefficient is the average of the coefficients at the six test frequencies. Note: Where metric conversions are desired, dimensions do not have to be exact. Chemicals, materials, parts, and equipment referenced in this document
21、 must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. Page 4 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 EVEREADY NO. 6 (OR EQUIV.) 1.5 VOLT - SOUND ABSORPTION TEST HELIPOT 10K fi 15 TURNS
22、 OUTPUT TO X - AXIS OF X-Y RECORDER I I I I io 4-MICROSWITCHES-, I I / (DRIVE MOTOR OUTPUT SHAFT) DOUBLE SHEAVE PULLEY i I l I I r I (MICROPHONE CARRIAGE DRIVE I PULLEY - CONNECTED TO 15 TURN I I HELIPOT SHAFT I I I l L _ I _- - Microphone Drive System - Sound Absorption Tunnel Figure 1 - FIGURE 1 F
23、IGURE 2 Page 5 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 SOUND ABSORPTION TEST MICROPHONE CARRIAGE SUPPORT BLOCK B A B C f 1 C 1 C y- PULLEY A - Steel Bar (1/2“ x 1“x 6) B - Felt Spacers (1/2“ thick) C - 2“ Aluminum Channel (1/4“ walls) Scale: Full Size
24、 Page 6 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 F SOUND ABSORPTION TEST I MICROPHONE CARRIAGE A B A n Scale: Full Size b-4 A - Steel Bar (1/2“ x 1“x 6) B - Felt Spacer (1/2“ thick) D - Felt Spacers (1/8“ thick) E - Nylon (3/16“ thick) F - Sponge Rubbe
25、r Spacers (5132“ thick) E Page 7 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 SOUND ABSORPTION TEST Page 8 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 SOUND ABSORPTION TEST SOUND ABSORPTION TUNNEL BARE (UNTREATE
26、D) TUNNEL TUNNEL TREATED WITH ACCUSTICAL MATERIAL Page 9 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 SOUND ABSORPTION TEST Page 10 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY TEST METHOD BV 003-05 MANUFACTURER SAMPLE NO TYPE OF INSU
27、LATION SOUND ABSORPTION TEST THICKNESS REPORT NO WEIGHT DATE O U T P U T I N D E C I B E L S O U T P U T I N D E C I B E L S COEFFICIENT FREQUENCY CPS 110 100 90 80 110 1 O0 90 80 MICROPHONE TRAVEL (IN x IO) PRINTED IN U SA Page 11 of 12 Copynght02001, Ford Global Technologies, Inc FORD LABORATORY T
28、EST METHOD BV 003-05 Black SOUND ABSORPTION TEST I I I I I I I I I I I I I I I I l I I l I I 5A I -2 t I 3 I t Reverse T I Orange Black I I Blue LS-1 LS-2 I +!? Red I ZJ -f 9 tlrov 23 fi, Yellow I MS-2 r- Black SOUND ABSORPTION TEST TUNNEL MICROPHONE DRIVE WIRING DIAGRAM Page 12 of 12 Copynght02001, Ford Global Technologies, Inc
