Duvall, Lowery D.

Ferebee, Robin C.

Harrison, Justin R.

LaVerde, Bruce T.

Scogin, Tyler M.

Smith, Andrew M.

Teague, David W.

NASA Technical Reports Server

© The Aerospace Corporation 2010
Comparison of Direct Acoustic Impingement of Avionics 
Equipment to Vibration Base Shake Response
Spacecraft and Launch Vehicle Dynamic Environments Workshop
20-22 June 2017
Tyler M. Scogin, Andrew M. Smith
Vibroacoustics Engineers
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
Lowery D. Duvall
Vibroacoustics Engineer
Propulsion Structures & Dynamics Analysis Branch (ER41)
NASA Marshall Space Flight Center
Bruce T. LaVerde,  ERC Inc
Vibroacoustics Lead Engineer
ESSSA Contract Support to 
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
Justin R. Harrison, CRM Solutions, Inc
Vibroacoustics Engineer
ESSSA Group Support to
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
Robin C. Ferebee
Vibroacoustics Engineer
ESSSA Group Support to
Propulsion Structures & Dynamics Analysis Branch (ER41)
NASA Marshall Space Flight Center
David W. Teague
Vibroacoustics Engineer
ESSSA Group Support to
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
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https://ntrs.nasa.gov/search.jsp?R=20170008155 2019-08-29T23:24:32+00:00Z
2Direct Impingement vs Vibration Base Shake
• Background
• Problem Statement
• Test and Observations
• Conclusions and Future Work
Agenda
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3Space Launch System (SLS)
• Space Launch System (SLS)
– NASA’s future manned Mars launch vehicle
• Launch vehicle developers may put components on isolators inside the vehicle
– For example, heritage hardware being used in new flight environments
• Typically components mounted on isolators require both vibration and acoustic testing
Background
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• Performing both tests may impact cost and schedule
– Risk of not performing acoustic qualification test
is that hardware could fail due to exposure to high 
acoustic environments
4Direct Acoustic Impingement Concern
X
1
1
X
• Vibration was assumed to be from external
panels which is structurally transmitted 
through isolator mounts. This was assumed 
to be the predominant source of vibration for 
components.
– This assumes effect of direct acoustic 
impingement on components is not the 
predominant source of vibration
1
2
X
– For isolated components, only considering structurally transmitted 
vibration ignores the potentially predominant source of vibration – direct 
acoustic impingement
• NASA Marshall Engineering conducted development tests to 
investigate this possibly non-conservative assumption
– This assumption is generally valid for non-
isolated components
– However, isolation significantly mitigates 
structural transmission of vibration
• Acoustic impingement may then be the 
predominant source of vibration
Inside vehicle
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Problem Statement
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5• Three avionics boxes representative of launch vehicle 
components were put through an acoustic test series
– Internal circuit boards and chassis were instrumented with 
accelerometers and strain gauges to measure vibration response
– Small box is heritage SRB flight hardware
• Then each box was vibration tested on a shaker table
• Allowed for comparison of response data between the acoustic 
test and vibration shaker table test responses
• Strain gauge data allowed for insight to subcomponent load 
factor development
RuggedizedLarge Small
Test Background
Test and Observations
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6Vibration levels
• Criteria 1 and 2 were generic test levels that were representative of compartment levels
• Criteria 3 was derived from SMC-S-016 minimum acceptance test +3 dB
Vibration responses
• Data collected for all 3 axes, however, data shown are only responses normal to circuit boards 
• Same locations as acoustic test
Vehicle Zone Vibration Test Cases
Forward Criteria 1, Criteria 3
Midsection Criteria 1, Criteria 2, Criteria 3
Aft Criteria 1, Criteria 3
5
3
1
Vibration Testing
Test and Observations
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7Acoustic levels
• 6 OASPL test cases: 140 dB, 143 dB, 147 dB, 150 dB, 153 
dB, 157 dB
• Levels chosen representative of three sections of where 
launch vehicle avionics are located (Forward, Midsection, Aft)
• Panel dimensions: 60” x 14.25” x 0.7” aluminum
Large
Small
Ruggedized
Acoustic Testing
Test and Observations
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140
145
150
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One Third Octave Center Frequency (Hz)
Microphone Input Criteria
143 dB Criteria (ECU -12 dB)
150 dB Critiera (ECU -6 dB)
157 dB Criteria (ECU MPE)
Forward Criteria (143 dB OASPL)
Midsection rit ia (150 dB OASPL)
Aft Criteria (157 dB OASPL)
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Vehicle Zone Acoustic Test SPL
Forward 143 dB OASPL
Midsection 150 dB OASPL
Aft 157 dB OASPL
5
3
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810 100 1000
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Frequency (Hz)
Direct Impingement Acoustic Test vs Shaker Test, Large Box Response R4X
Forward 143 dB OASPL
143 dB acoustic scaled
Non FTS qual input
Non FTS qual shaker 0 dB
Min accept input
Min accept shaker 0 dB
 Base shake response envelopes acoustic response
Criteria 1 input
Criteria 1 shaker 0 dB
Criteria 3 input
Criteria 3 shaker 0 
Forward (143 dB): Accelerometer R4X
Test and Observations
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(Data is typical response from all three boxes)
910 100 1000
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Frequency (Hz)
Direct Impingement Acoustic Test vs Shaker Test, Large Box Response R4X
Midsection 150 dB OASPL
150 dB acoustic scaled
FTS qual input
FTS qual shaker 0 dB
Non FTS qual input
Non FTS qual shaker 0 dB
Min accept input
Min accept shaker 0 dB
 Acoustic response approaching base shake response
Criteri 2 input
Criteri 2 shaker 0 dB
Criteria 1 input
Criteria 1 shaker 0 dB
Criteria 3 input
Criteria 3 shaker  
Midsection (150 dB): Accelerometer R4X
Test and Observations
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(Data is typical response from all three boxes)
10
10 100 1000
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Frequency (Hz)
Direct Impingement Acoustic Test vs Shaker Test, Large Box Response R4X
Aft 157 dB OASPL 
157 dB acoustic scaled
Non FTS qual input
Non FTS qual shaker 0 dB
Min accept input
Min accept shaker 0 dB
 Maximum acoustic response of fundamental board resonances is 
enveloped by base shake vibration
 Minor exceedance is deemed acceptable
 Criteria 3 (minimum acceptance + 3 dB) conservatively envelopes the 
flight environment prediction
Criteria 1 input
Criteria 1 shaker 0 dB
Criteria 3 input
Criteria 3 shaker  
Aft (157 dB): Accelerometer R4X
Test and Observations
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(Data is typical response from all three boxes)
11
Conclusions and Future Work
Conclusions:
• Acoustic and vibration shaker table accelerometer responses were assessed and compared 
• Test data showed base shake vibration response envelopes acoustic induced vibration response 
in Forward & Midsection zones
• Aft zone acoustic responses greater than vibration response at some higher frequencies; 
however, there is still adequate margin in test criteria
• Structurally transmitted vibration is still the predominant source of vibration for isolated 
components of comparable size and construction as those tested in this series for 
acoustic levels up to ~157 dB OASPL
General recommendation:
• Include a minimum random vibration criteria for qualification of isolated hardware on future 
programs to avoid acoustic qualification tests
Future Work:
• Analyze strain gauge data gathered in this testing to aid in FEM correlation of avionics 
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12
Backup
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13
Strain measurements were collected on the boards at key interface locations
• Key interface locations were considered near a mounting stud or edge clamp
Vibration responses were also measured on the boards
• Measurement locations were taken near the center of the boards
Mounting Studs to Middle 
Rib on Opposite Side
Edge Clamp
Two orthogonal 
strain measurements
Strain Gauge Response Measurements
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14
Strain Gauge Response Measurements
• Preliminary results reveal same correlation of cumulative RMS velocity and RMS strain as 
seen with larger secondary structures
• Forward work is to further interrogate board measurements and bring back design insights to 
2018 SCLV
• Any analysis request from the community are welcome
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© The Aerospace Corporation 2010
Comparison of Direct Acoustic Impingement of Avionics 
Equipment to Vibration Base Shake Response
Spacecraft and Launch Vehicle Dynamic Environments Workshop
20-22 June 2017
Tyler M. Scogin, Andrew M. Smith
Vibroacoustics Engineers
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
Lowery D. Duvall
Vibroacoustics Engineer
Propulsion Structures & Dynamics Analysis Branch (ER41)
NASA Marshall Space Flight Center
Bruce T. LaVerde,  ERC Inc
Vibroacoustics Lead Engineer
ESSSA Contract Support to 
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
Justin R. Harrison, CRM Solutions, Inc
Vibroacoustics Engineer
ESSSA Group Support to
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
Robin C. Ferebee
Vibroacoustics Engineer
ESSSA Group Support to
Propulsion Structures & Dynamics Analysis Branch (ER41)
NASA Marshall Space Flight Center
David W. Teague
Vibroacoustics Engineer
ESSSA Group Support to
Dynamics, Loads and Strength Branch (EV31)
NASA Marshall Space Flight Center
APPROVED FOR PUBLIC RELEASE – DISTRIBUTION IS UNLIMITED
© The Aerospace Corporation 2010
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Comparison of Direct Acoustic Impingement of Avionics Equipment to Vibration Base Shake Response

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