515.8 ACOUSTIC NOISE CONTENTS
| Paragraph | Page | |
|---|---|---|
| 1. | SCOPE | 1 |
| 1.1 | PURPOSE | 1 |
| 1.2 | APPLICATION | 1 |
| 1.3 | LIMITATIONS | 1 |
| 2. | TAILORING GUIDANCE | 1 |
| 2.1 | SELECTING THE ACOUSTIC NOISE METHOD | 1 |
| 2.1.1 | EFFECTS OF THE ACOUSTIC NOISE ENVIRONMENT | 1 |
| 2.1.2 | SEQUENCE AMONG OTHER METHODS | 2 |
| 2.2 | SELECTING PROCEDURES | 2 |
| 2.2.1 | PROCEDURE SELECTION CONSIDERATIONS | 2 |
| 2.2.2 | DIFFERENCE AMONG PROCEDURES | 2 |
| 2.3 | DETERMINE TEST LEVELS AND CONDITIONS | 3 |
| 2.3.1 | GENERAL | 3 |
| 2.3.2 | USE OF MEASURED AND RELATED DATA | 3 |
| 2.3.3 | TYPES OF ACOUSTIC EXCITATION | 3 |
| 2.3.3.1 | DIFFUSE FIELD | 4 |
| 2.3.3.2 | GRAZING INCIDENCE ACOUSTIC NOISE | 4 |
| 2.3.3.3 | CAVITY RESONANCE | 4 |
| 2.3.3.4 | ADDITIONAL TECHNICAL GUIDANCE | 4 |
| 2.4 | TEST ITEM CONFIGURATION | 4 |
| 3. | INFORMATION REQUIRED | 4 |
| 3.1 | PRETEST | 5 |
| 3.2 | DURING TEST | 5 |
| 3.3 | POST-TEST | 5 |
| 4. | TEST PROCESS | 5 |
| 4.1 | TEST FACILITY | 5 |
| 4.2 | CONTROLS | 6 |
| 4.2.1 | CONTROL OPTIONS | 6 |
| 4.2.1.1 | SINGLE POINT NOISE CONTROL | 6 |
| 4.2.1.2 | MULTIPLE POINT NOISE CONTROL | 6 |
| 4.2.1.3 | VIBRATION RESPONSE CONTROL | 6 |
| 4.2.2 | CONTROL METHODS | 6 |
| 4.2.3 | OVERALL ACCURACY OF CONTROL | 6 |
| 4.2.4 | CALIBRATION AND TOLERANCE | 6 |
| 4.3 | TEST INTERRUPTION | 7 |
| 4.3.1 | INTERRUPTION DUE TO LABORATORY EQUIPMENT MALFUNCTION | 7 |
| 4.3.2 | INTERRUPTION DUE TO TEST ITEM OPERATION FAILURE | 7 |
| 4.4 | TEST SETUP | 7 |
| 4.5 | TEST EXECUTION | 7 |
| 4.5.1 | PREPARATION FOR TEST | 7 |
MIL-STD-810H
METHOD 515.8
CONTENTS - Continued Paragraph Page
| Paragraph | Page | |
|---|---|---|
| 4.5.1.1 | PRELIMINARY STEPS | 7 |
| 4.5.1.2 | PRETEST STANDARD AMBIENT CHECKOUT | 7 |
| 4.5.2 | INSTALLATION OF THE TEST ITEM | 7 |
| 4.5.2.1 | DIFFUSE FIELD | 7 |
| 4.5.2.2 | GRAZING INCIDENCE ACOUSTIC NOISE | 8 |
| 4.5.2.3 | CAVITY RESONANCE ACOUSTIC NOISE | 8 |
| 4.5.3 | PROCEDURE I - DIFFUSE FIELD ACOUSTIC NOISE TESTING | 8 |
| 4.5.3.1 | PROCEDURE Ia - UNIFORM INTENSITY ACOUSTIC NOISE TESTING | 8 |
| 4.5.3.2 | PROCEDURE Ib - DIRECT FIELD ACOUSTIC NOISE TESTING | 9 |
| 4.5.4 | PROCEDURE II - GRAZING INCIDENCE ACOUSTIC NOISE TESTING | 9 |
| 4.5.5 | PROCEDURE III - CAVITY RESONANCE ACOUSTIC NOISE TESTING | 10 |
| 5. | ANALYSIS OF RESULTS | 10 |
| 6. | REFERENCE/RELATED DOCUMENTS | 10 |
| 6.1 | REFERENCED DOCUMENTS | 10 |
| 6.2 | RELATED DOCUMENTS | 10 |
TABLE
TABLE 515.8-I. TEST TOLERANCES
METHOD
515.8 ANNEX A GUIDANCE FOR INITIAL TEST SEVERITY
| 1. | BROADBAND RANDOM AND INCIDENCE NOISE TESTING | A-1 |
| 1.1 | OVERALL SOUND PRESSURE LEVEL (OASPL) | A-1 |
| 1.2 | TEST SPECTRUM | A-2 |
| 1.3 | SIMULATION OF AERODYNAMIC TURBULENCE | A-3 |
| 2. | CAVITY RESONANCE TESTING | A-3 |
| 3. | EXTERNAL STORES TESTING | A-4 |
| 3.1 | TEST SPECTRUM | A-4 |
| 3.2 | TEST PARAMETERS | A-5 |
ANNEX A FIGURES
| FIGURE 515.8A-1. | APPLIED TEST SPECTRUM | A-2 |
| FIGURE 515.8A-2. | TYPICAL STORE PROFILE | A-4 |
| FIGURE 515.8A-3. | ONE-THIRD OCTAVE BAND SPECTRUM FOR ASSEMBLED EXTERNALLY CARRIED AIRCRAFT STORES | A-4 |
MIL-STD-810H
METHOD 515.8
CONTENTS - Continued Paragraph
Page
| ANNEX A TABLES | ||
|---|---|---|
| TABLE 515.8A-I. | OVERALL SOUND PRESSURE LEVELS AND DURATIONS | A-1 |
| TABLE 515.8A-II. | ONE-THIRD OCTAVE BAND LEVELS FOR FIGURE 515.8A-1 | A-2 |
| TABLE 515.8A-III. | CAVITY RESONANCE TEST CONDITIONS (SEE PARAGRAPH 6.1, REFERENCE A) | A-3 |
| TABLE 515.8A-IV. | SUGGESTED ACOUSTIC TEST LEVELS FOR ASSEMBLED EXTERNALLY CARRIED AIRCRAFT STORES | A-5 |
METHOD
515.8 ANNEX B ADDITIONAL TECHNICAL GUIDANCE
| 1. | REVERBERATION CHAMBERS | B-1 |
| 2. | PROGRESSIVE WAVE TUBES | B-1 |
| 3. | ACOUSTIC NOISE CHARACTERISTICS | B-1 |
| 4. | CONTROL STRATEGIES | B-1 |
| 5. | DEFINITIONS | B-2 |
| 5.1 | Sound Pressure Level | B-2 |
| 5.2 | Third Octave Filters | B-2 |
| 6. | DIRECT FIELD ACOUSTIC TEST CHARACTERISTICS | B-2 |
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MIL-STD-810H METHOD 515.8
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MIL-STD-810H
METHOD 515.8
METHOD
515.8 ACOUSTIC NOISE
NOTE: Tailoring is essential. Select methods, procedures, and parameter levels based on the tailoring process described in Part One, paragraph 4.2.2, and Annex C. Apply the general guidelines for laboratory test methods described in Part One, paragraph 5 of this Standard.
515.8 ANNEX A
METHOD 515.8, ANNEX A
GUIDANCE FOR INITIAL TEST SEVERITY
515.8 ANNEX A
515.8 ANNEX A
515.8 ANNEX A
515.8 ANNEX B
METHOD 515.8, ANNEX B
ADDITIONAL TECHNICAL GUIDANCE
515.8 ANNEX B
response. Provide for averaging the outputs of the microphones to provide the spatial average of the noise for control purposes.
515.8 ANNEX B
the composite control average and + 3dB at each control microphone relative to the reference spectrum for overall levels in the 125 to 145dB range. See paragraph 6.1, reference e for more information about SISO and MIMO control.
As stated in paragraph 2.2.2.a.Ib, DFAN testing does not create an environment that is identical to a reverberant chamber. However, DFAN testing can produce a very similar structural response. Paragraph 6.1, reference f gives a detailed comparison of the results from a DFAN test with those from reverberant testing for a typical spacecraft structure subjected to a typical launch vehicle environment. Similar configurations can be expected to produce similar results. Structures and/or environments that vary greatly from those documented may require similar study and evaluation before implementing the DFAN approach.
Lastly, a restriction on run time for test levels above 144dB is usually imposed due to heat build-up in the driving coils of the acoustic drivers. Currently technology limits runs at 140 to 144dB to about one minute and runs above 144dB to about 30 seconds. If run times longer than these are required, it is recommended that the total test time be broken into multiple segments of 30 seconds each until the total run time is accumulated.
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MIL-STD-810H METHOD 515.8 ANNEX B
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