William O. Hughes, Mark E. McNelis, Aron D. Hozman, and Anne M. McNelis

Glenn Research Center, Cleveland, Ohio

The Testing Behind the Test Facility:

The Acoustic Design of the NASA Glenn

Research Center’s World-Class Reverberant

Acoustic Test Facility

NASA/TM—2010-216802

October 2010
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William O. Hughes, Mark E. McNelis, Aron D. Hozman, and Anne M. McNelis

Glenn Research Center, Cleveland, Ohio

The Testing Behind the Test Facility:

The Acoustic Design of the NASA Glenn

Research Center’s World-Class Reverberant

Acoustic Test Facility

NASA/TM—2010-216802

October 2010

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Acknowledgments

The authors would like to acknowledge the NASA SET Project Offi ce for their continuing support and funding for the test programs 

discussed in this paper. The extensive contributions of the following organizations and individuals are particularly worthy of

mention for their substantial role in this testing and the test data analysis effort: Benham Companies, LLC: Neil Waggoner, Josh 

Loehrke; Aiolos Engineering Corporation: Ralph Leitner, Dr. Gary Elfstrom, Dr. Ramani Ramakrishnan, Alex Holzwarth, Sergio 

Raimondo; TEAM Corporation: Bob Tauscher, Bill Woyski, Chon Mech; Wyle Laboratories: Dr. Costa Glaretas, Chito Hermoso; 

m+p International: Al Prosuk, Guido Bossaert; Cambridge Collaborative Incorporated: Dr. Jerry Manning; Dr. Patricia Manning, 

National Research Council: Dr. David Zimcik, Dr. Anant Grewal, Dr. Eric Chen, Viresh Wickramasinghe, Brent Lawrie, Luc 

Hurtubise; Redstone Technical Test Center: Dr. Mike Hale; Owens Corning: Kevin Herreman, Don Hill

Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

Available electronically at http://gltrs.grc.nasa.gov

Trade names and trademarks are used in this report for identifi cation 

only. Their usage does not constitute an offi cial endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

Level of Review: This material has been technically reviewed by technical management. 
NASA/TM—2010-216802 1 

The Testing Behind the Test Facility: The Acoustic Design 

of the NASA Glenn Research Center’s World-Class 

Reverberant Acoustic Test Facility 

William O. Hughes, Mark E. McNelis, Aron D. Hozman, and Anne M. McNelis 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is 

leading the design and build of the new world-class vibroacoustic test capabilities at the NASA GRC’s 

Plum Brook Station in Sandusky, Ohio, U.S.A. Benham Companies, LLC is currently constructing 

modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of 

NASA’s space exploration program. 

The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3

 in volume 

and capable of achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. 

This combination of size and acoustic power is unprecedented amongst the world’s known active 

reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra for a range of 

many NASA space flight environments in the RATF is the knowledge gained from a series of ground 

acoustic tests. Data was obtained from several NASA-sponsored test programs, including testing 

performed at the National Research Council of Canada’s acoustic test facility in Ottawa, Ontario, Canada, 

and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, U.S.A. The 

majority of these tests were performed to characterize the acoustic performance of the modulators (noise 

generators) and representative horns that would be required to meet the desired spectra, as well as to 

evaluate possible supplemental gas jet noise sources. The knowledge obtained in each of these test 

programs enabled the design of the RATF sound generation system to confidently advance to its final 

acoustic design and subsequent ongoing construction. 

Introduction 

The NASA Space Environmental Test (SET) Project is tasked to develop new environmental test 

facilities to support NASA’s developing space exploration program. The Space Power Facility (SPF) at 

the NASA Glenn Research Center’s Plum Brook Station in Sandusky, Ohio, U.S.A. is already the home 

of the world’s largest thermal vacuum chamber. In order to provide one-stop testing for the suite of space 

environmental testing, the SPF is being augmented through the NASA SET Project Office with new 

reverberant acoustic (Ref. 1), mechanical vibration (Ref. 2), and modal test (Ref. 2) facilities. 

In August 2007, Benham Companies, LLC (Benham), located in Oklahoma City, Oklahoma, U.S.A., 

won the NASA prime contract to design and construct the acoustic, vibration and modal test facilities, as 

well as to provide the high speed data acquisition system to support these facilities. Benham contracted 

with Aiolos Engineering Corporation (Aiolos), located in Toronto, Ontario, Canada to provide the 

acoustic design of the Reverberant Acoustic Test Facility (RATF). This paper addresses the various 

acoustic test programs that advanced the acoustic design of the RATF. 
NASA/TM—2010-216802 2 

Figure 1.—Acoustic test spectra requirements. 

RATF Requirements 

The key requirements for the RATF acoustic design were as follows: 

 The RATF shall be physically as large as possible within the given space limitations of SPF. 

 The RATF’s test chamber shall be properly sized to acoustically test four space vehicle 

configurations, encompassing an 18-ft diameter test article, and a 47-ft tall test article. 

 The RATF’s test chamber shall physically allow a 32.8-ft diameter test article weighing up to 

120,000 lb. 

 The RATF shall generate the empty chamber acoustic test spectra shown in Figure 1, for 

continuous test duration of 10 min. These eight (8) “C” spectra represent a wide range of current 

and future NASA missions, including five (5) spectra with a 163 dB OASPL. 

 The RATF shall include an independent, multi-channel digital acoustic control system capable of 

controlling the noise sources to the sound pressure levels (SPL) and spectra shown in Figure 1, 

within specified tolerances (+5 dB below the 50 Hz one-third octave bands (OTOB), +3 dB 

covering 50 Hz to 2K Hz OTOB’s, +5 dB above 2K Hz OTOB’s, +1.5 dB on OASPL). 

RATF Chamber Sizing and Initial Acoustic Modulator Selection 

The physical size of the RATF was determined from the maximum available space within the SPF, 

along with following guidelines on proper room ratios and good acoustic test practices. Benham and 

Aiolos ultimately designed a reverberant acoustic test chamber with the following dimensions: 47.5-ft 

long by 37.5-ft wide by 57-ft high. After accounting for the main chamber door jamb structure the 

resulting chamber volume is 101,189 ft3

. 

The next design issue was to determine the number and type of acoustic modulators or noise 

generators that would be needed to create the enormous sound power necessary to sustain the high SPL in 

this large chamber volume. Prior to the “C” acoustic spectra requirements becoming effective in 

September 2008, six other spectra were originally required including three spectra whose characteristics 

and SPL were very similar to the C2 spectra. As seen in Figure 1, C2 is particularly challenging due to its 

110.0

115.0

120.0

125.0

130.0

135.0

140.0

145.0

150.0

155.0

160.0

10 100 1000 10000 1/3 Octave Frequency

SPL [dB] SPL (dB) re: 20 μPa

(Hz)

C1 

C2 

C3 

C4 

C5 

C6 

C7 

C8 

1/3 Octave Band Frequency (Hz)
NASA/TM—2010-216802 3 

very high SPL at frequencies below 100 Hz. This need led Benham and Aiolos to initially select the 

TEAM Corporation (TEAM) modulators known as the MK-VI and MK-VII, and propose using horns 

with three different cut-off frequencies (25, 35, and 50 Hz) for the RATF design. The TEAM modulators, 

although not widely utilized within the reverberant acoustic industry, are especially effective at the low 

frequencies (at or below the 125 Hz OTOB) with a rated modulator acoustic power of 150 and 200 kW, 

respectively. 

Although the TEAM modulators have been in service for over 50 years, there was not much acoustic 

characterization data available on them. To obtain characterization data, and to qualify and mitigate any 

associated risk, Aiolos, jointly with staff at the National Research Council of Canada (NRC) designed and 

conducted a test program at the Ottawa NRC reverberant acoustic test facility. 

Initial NRC Testing, Part 1 (Aiolos) 

 Date: December 2007 to January 2008 

 Location: Reverberant acoustic chamber at the NRC, Ottawa, Ontario, Canada. NRC’s chamber 

is 32-ft long by 22.6-ft wide by 26.3-ft high, with a volume of ~19,000 ft3

. 

 Objectives: a) Validate the acoustic performance and obtain operating parameters of the TEAM 

modulators, b) Obtain acoustic test data to benchmark RATF’s acoustic predictions. 

 Equipment: a) MK-VI and MK-VII modulators, b) 25 and 100 Hz horns 

 Findings: a) MK-VI and MK-VII modulators achieved the published acoustic power, b) No 

major impact of modulator supply pressure on acoustic performance was observed, c) Two 

modulators operating simultaneously on two horns, result in the same acoustic output as the 

acoustic sum of two modulators operating individually, d) Results for two modulators operating 

on one horn via a Y-adaptor produced less than the expected doubling, e) The modulator’s output 

varied linearly with input gain, f) The modulator’s bias setting (a measure of the force required to 

hold the modulator valve closed) requires further exploration to optimize its effect on noise 

generation, g) Two modulator shaft failures occurred. 

 Go-forward plan: a) The TEAM modulator’s performance, especially at low frequencies, 

showed promise for meeting the RATF requirements, b) Need for additional understanding of 

affect of bias, c) Need to instrument the modulator shaft to understand modulator failure that was 

then believed to be due to assembly workmanship. 

Initial NRC Testing, Part 2 (Aiolos) 

 Date: April 2008 

 Location: Reverberant acoustic chamber at the NRC, Ottawa, Ontario, Canada 

 Objectives: a) Examine quantitative relation of bias to modulator efficiency and spectral control, 

b) Utilize various spectral input signal shapes for open loop testing, c) Add gas accumulator to 

stabilize supply gas pressure variations, d) Instrument TEAM modulator shaft with strain gauges 

to provide data to assess previous shaft failures. 

 Equipment: a) MK-VI, MK-VII modulators, b) 25, 100, and 200 Hz horns 

 Findings: a) Confirmed minimal effect of gas supply pressure, b) TEAM modulators were 

controllable from the 25 to 500 Hz OTOB, c) Optimal bias setting produced peak acoustic 

performance, d) Demonstrated excellent repeatability in acoustic performance, e) Performance 

between the 630 to 800 Hz OTOB is due to non-linear spillover and flow noise, f) Performance 

with the 200 Hz horn was poor due to inadequate connections and subsequent gas flow problems, 

and g) One additional modulator shaft failure occurred. 

 Go-forward plan: a) TEAM Modulators controllability, repeatability and acoustic performance 

is sufficient for RATF design, especially at low to mid frequencies, b) Shaft failures of TEAM 

modulators pointed to reliability issues and need to reanalyze and redesign shaft. 
NASA/TM—2010-216802 4 

Redstone Testing (NASA) 

Due to the TEAM modulator’s shaft reliability issues, the lack of credible data from a high frequency 

horn (greater than 100 Hz), and continuing external questions on the controllability and acoustic 

performance of the TEAM modulators, NASA GRC performed its own independent test program to 

obtain additional acoustic test data and experience with the TEAM modulator (Ref. 3). Since the U.S. 

Army’s Redstone Arsenal has many years of experience with the TEAM modulator it was chosen by 

NASA GRC as the test site. 

 Date: May 2008 

 Location: Reverberant acoustic chamber at the U.S. Army Redstone Technical Test Center 

(RTTC) in Huntsville, Alabama, U.S.A. The Redstone Arsenal chamber is 28.5-ft long by 24.3-ft 

wide by 18.0-ft high, with a volume of ~12,500 ft3

. 

 Objectives: a) Obtain independent verification of the TEAM modulator acoustic performance 

(controllability, shape-ability, and repeatability), b) Collect data on two additional horn sizes 

(50 and 167 Hz), c) Compare the response of the TEAM modulator in two facilities (RTTC and 

NRC), d) Compare the response of the TEAM MK-VI and the Wyle Laboratories’ WAS3000 

modulators at the same facility (RTTC). 

 Equipment: a) MK-VI modulator, b) WAS3000 modulator, c) 50 and 167 Hz horns 

 Findings: a) Confirmed the NRC test findings of controllability, shape-ability and repeatability 

for the TEAM modulator, b) TEAM modulator performed well with the 167 Hz horn, c) Test data 

validated the analytical scaling procedures for using data in one chamber to predict the response 

in a different chamber, d) Test data confirmed superposition of modulators’ output, e) The 

acoustic output of the MK-VI TEAM modulator was higher than that of the WAS3000 modulator 

by 6 to 7 dB at 25 to 100 Hz OTOB; similar from 125 to 1000 Hz OTOB; and higher by 2 to 3 dB 

from 1000 to 8000 Hz OTOB due to non-linear spillover. Both modulators allowed the generation 

of shaped spectra by controlling the input signal from 50 to 630 Hz. 

 Go-forward plan: a) Pending a successful resolution of TEAM Modulator shaft failures, 

incorporate TEAM modulators into the RATF design, b) In addition to previously planned use of 

low frequency horns, incorporate 160 Hz horn for RATF design. 

Phase 1 Testing at NRC (Aiolos) 

Once the C-curve acoustic requirements (Fig. 1) replaced the original acoustic requirements in 

September 2008 it became necessary to revisit the previous horn selection and related acoustic design, 

and augment the TEAM noise generators with additional high frequency sources. Additionally, test 

verification of the closed loop control of the TEAM modulators was planned as part of a new two-phase 

test program. Finally, the TEAM modulator shaft was extensively redesigned to avoid fatigue life issues 

and this new design and its performance needed to be test verified. 

 Date: March to April 2009 

 Location: Reverberant acoustic chamber at NRC, Ottawa, Ontario, Canada 

 Objectives: a) Examine the acoustic performance of impinging gas jets, proposed as one 

alternative to the required high frequency noise sources, including their controllability, and other 

design features such as impinging plates and means for minimizing screech tones, b) Reconfirm 

TEAM modulator’s acoustic performance and life reliability with new shaft design, c) Perform 

closed loop control of a single TEAM modulator, and d) Quantify the dynamic range of the 

TEAM modulator. 

 Equipment: a) MK-VI and MK-VII modulators, b) 25 and 160 Hz horns, c) Gas jets with various 

nozzle diameters, adjustable support frames, impingement plates, reflectors and chevrons 
NASA/TM—2010-216802 5 

 Findings: a) Gas jets were able to produce high sound pressure levels but generally only in the 

presence of intense screech tonal noise. Reduction of screech tones was possible using vortex tabs 

and chevrons at the nozzle exit but at the expense of significantly reduced OASPL. The expected 

benefit of impinging plates to amplify sound, and reflectors to reduce the screech tones were not 

observed (Refs. 4 and 5). Significantly more jets than originally expected, and accompanying gas 

flow, would be needed to satisfy RATF requirements, b) Endurance testing of the TEAM 

modulator demonstrated that the shaft problem was resolved through the redesign; the measured 

stress levels were greatly reduced and very close to the predicted levels by TEAM Corporation, c) 

Testing also confirmed that the shaft redesign caused no significant change in the acoustic 

performance, d) Closed loop control testing of the TEAM modulator with the NRC control 

software was successful, e) The dynamic range was found to be ~6 to 9 dB for the MK-VI and 

~9 to 12 dB for the MK-VII modulators. 

 Go-forward plan: a) Incorporate TEAM modulators into RATF design, b) To add robustness to 

the RATF design to handle future spectra, increase the number of horns types (incorporate several 

different horn cutoff frequencies for RATF design), c) Gas jets are not to be incorporated, but 

instead evaluate the proposal to incorporate the Wyle WAS5000 modulator (similar to Ling EPT200 modulator), d) Aiolos to proceed with contract to select acoustic control system (ACS) for 

RATF and to demonstrate the ACS performance in the Phase 2 testing at NRC. 

Phase 2 Testing at NRC (Aiolos) 

 Date: October 2009 

 Location: Reverberant acoustic chamber at NRC, Ottawa, Ontario, Canada 

 Objectives: a) Characterize the Wyle Laboratories WAS5000 modulator acoustic performance in 

a similar manner as the TEAM modulator, including investigating the use of an extension spool 

between the WAS5000 modulator and horn, b) Demonstrate the operation of the m+p 

International ACS, including the simultaneous closed loop control of the three modulators 

(TEAM MK VI and MK VII, Wyle WAS5000). 

 Equipment: a) MK-VII modulator on 25 Hz horn, b) MK VI modulator on 100 Hz horn, 

c) WAS5000 modulator on 250 Hz horn, d) m+p International ACS 

 Findings: a) WAS5000 modulator’s acoustic performance met or exceeded the expectations 

going into this test, b) The spool piece is not needed, c) The m+p ACS performed very well 

controlling three modulators simultaneously meeting the specified test tolerances, stability and 

ramp-up rates. Given the fact that there were only 3 modulators and 3 horns the ACS exceeded 

expectations in demonstrating compliance to a variety of acoustic spectra, including the scaled 

down C-curve acoustic spectral shapes. 

 Go-forward plan: a) Incorporate the WAS5000 modulators on a 250 Hz horn into the RATF 

design, b) Incorporate the m+p ACS system into the RATF design. 

Paint Absorption Testing at Owens Corning (NASA) 

The last remaining key parameter to benchmark was the acoustic absorption of the RATF chamber. In 

particular, the acoustic absorption of the wall paint planned by Benham for the RATF interior surfaces is 

an important factor to the RATF’s SPL at the mid to high frequencies (200 to 3000 Hz OTOB). NASA 

wanted to measure this absorption (Refs. 6 and 7) for the Benham selected paint as part of the NASA risk 

mitigation efforts to further establish confidence in the RATF predictions. Cambridge Collaborative 

Incorporated (CCI) led and performed this test for NASA. 

 
NASA/TM—2010-216802 6 

 Date: February to March 2010 

 Location: Small reverberant acoustic chamber at Owens Corning’s Acoustic Research Center, 

Granville, Ohio. The Owens Corning chamber is 20.9-ft long by 14.7-ft wide by 12.7-ft high, 

with a volume of ~3,900 ft3

. 

 Objectives: a) Measure the acoustic absorption of the Owens Corning chamber painted with the 

proposed RATF paint. b) Compare results with expectations and values used in Aiolos’ SPL 

predictions for RATF. 

 Equipment: a) Chamber coated with Benham proposed RATF paint, b) B&K (Bruel and Kjaer) 

sound source, c) Loudspeakers 

 Findings: a) Measured test data and subsequent decay rate analysis indicates that the selected 

paint has absorption characteristics consistent with expectations and with predicted analytical 

values used by Aiolos for their RATF acoustic predictions and design. 

 Go-forward plan: a) Approve the paint selected by Benham for use in RATF chamber. 

Conclusions 

From the beginning, Benham, Aiolos and NASA have agreed that it was important to ground the 

acoustic predictions of the RATF chamber with actual test data. This was especially important given the 

extreme SPL required for RATF, as well as the lack of available performance data for the TEAM MK-VI 

and MK-VII and the Wyle WAS5000 acoustic modulators. Therefore as explained in this paper, 

numerous and extensive test programs were completed to obtain the necessary test data to benchmark the 

RATF acoustic predictions. These test series have provided NASA with the confidence to proceed with 

the Benham and Aiolos design for RATF. 

The overall layout and key properties of the RATF chamber and horn room are illustrated in Figure 2. 

There will be a total of 36 modulators and 36 horns to produce the acoustic power to meet the RATF 

requirements. The RATF design has eleven (11) MK-VII modulators distributed on the 25, 35, 50, and 

80 Hz horns, twelve (12) MK-VI modulators distributed on the 100 and 160 Hz horns, and thirteen (13) 

WAS5000 modulators on the 250 Hz horns. In order to meet the gaseous nitrogen (GN2) flow rate needs 

for these 36 modulators a vaporizer capable of a GN2 flow rate of 72,000 SCFM (standard cubic feet per 

minute) will be used. 

Due to physical limitations within the SPF all the horns will be located on the shared horn room/test 

chamber wall. The final layout of the 36 horns is shown in Figure 3. If it ever becomes necessary to 

increase the number of horns/modulators, there are scarring plans which will allow for an additional 

seven (7) WAS5000 modulators to be installed, as well as additional horn room wall space for future 

expansion. The chamber walls, ceiling and foundation have been designed and built to withstand up to 

166 dB OASPL. 

Benham is scheduled to complete the construction of the RATF by early autumn 2010. There will 

then be a period of several months where Benham will complete their verification testing of the facility, 

prior to turning the RATF over to NASA. NASA then plans on performing a series of internal tests, with 

an “available for customer testing” target date of the autumn of 2011. 

NASA has high confidence that through the extensive series of acoustic tests summarized in this 

paper, the RATF will perform to its expected requirements. It is anticipated that the most difficult 

acoustic spectra to meet will be the C8 curve (spectra with two peaks at 100 and 800 Hz), especially 

between 1000 to 2000 Hz. Due to its combination of very high chamber sound pressure levels and large 

volume, the RATF will be the world’s most powerful reverberant acoustic test facility. 
NASA/TM—2010-216802 7 

Figure 2.—RATF acoustic design. 

Figure 3.—RATF horn wall layout. 

Chamber Properties

Chamber Size 47.5 ft L x 37.5 ft W x 57 ft H

Chamber Volume 101,189 ft3

Acoustic Modulators 23 TEAM Modulators &

13 WAS 5000 Modulators

Horns 36 (grouped at 7 different 

horn cut-off frequencies)

Nominal GN2 flow 

rate

72,000 scfm 

Main Door Opening 34.5 ft wide

Number of Main 

Doors

2

Door Type Sliding and hinged

OASPL, empty 163 dB OASPL

Space Available for Future 

Expansion

25 

HZ

25 

HZ

50 

HZ

50 

HZ

50 

HZ

50 

HZ

35 

HZ

35 

HZ

160 

HZ

160 

HZ

160 

HZ

160 

HZ

160 

HZ

160 

HZ

160 

HZ

160 

HZ

80 

HZ

80 

HZ

80 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

250 

HZ

100 

HZ

100 

HZ

100 

HZ

100 

HZ

Scarring

(for 250 Hz)
NASA/TM—2010-216802 8 

References 

1. W.O. Hughes, M.E. McNelis, A.D. Hozman, and A.M. McNelis, “Status and Design Features of the 

new NASA GRC Reverberant Acoustic Test Facility (RATF),” Proceedings of the 2010 IEST Annual 

Technical Meeting, ESTEC 2010, 3–6 May 2010, Reno, NV, U.S.A. 

2. K.D. Otten, V.J. Suarez, and D.K. Le, “Status and Design Features of the new NASA GRC 

Mechanical Vibration Facility (MVF),” Proceedings of the 2010 IEST Annual Technical Meeting, 

ESTEC 2010, 3–6 May 2010, Reno, NV, U.S.A. 

3. M.T. Hale, “NASA Acoustic Trials Conducted at the RTTC Acoustic Test Facility,” Letter Report 

LR-RT-M-DY-08-69, June 17, 2008. 

4. R. Ramakrishnan, S. Raimondo, A. Grewal, G. Elfstrom, “High frequency noise generation by 

impinging jets,” Inter-Noise 2009, 23–26 August 2009, Ottawa, Ontario, Canada. 

5. R. Ramakrishnan, S. Raimondo, A. Grewal, G. Elfstrom, “Screech Suppression of Supersonic Jet 

Noise,” Journal of Canadian Acoustics 37, No. 3, 86–87 (2009). 

6. ASTM C423-09a, ASTM International Standard Test Method for Sound Absorption and Sound 

Absorption Coefficients by the Reverberation Room Method. 

7. ISO 354, Second edition 2003-05-15, International Standard on Acoustics—Measurement of sound 

absorption in a reverberation room (Reference number ISO 354:2003(E)). 
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Society for Experimental Mechanics, Inc., Jacksonville, Florida, January 31 to February 3, 2011. 

14. ABSTRACT

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) is leading the design and build of the new

world-class vibroacoustic test capabilities at the NASA GRC’s Plum Brook Station in Sandusky, Ohio, U.S.A. Benham Companies, LLC is 

currently constructing modal, base-shake sine and reverberant acoustic test facilities to support the future testing needs of NASA’s space 

exploration program. The large Reverberant Acoustic Test Facility (RATF) will be approximately 101,000 ft3 in volume and capable of 

achieving an empty chamber acoustic overall sound pressure level (OASPL) of 163 dB. This combination of size and acoustic power is 

unprecedented amongst the world’s known active reverberant acoustic test facilities. The key to achieving the expected acoustic test spectra 

for a range of many NASA space flight environments in the RATF is the knowledge gained from a series of ground acoustic tests. Data was 

obtained from several NASA-sponsored test programs, including testing performed at the National Research Council of Canada’s acoustic 

test facility in Ottawa, Ontario, Canada, and at the Redstone Technical Test Center acoustic test facility in Huntsville, Alabama, U.S.A. The 

majority of these tests were performed to characterize the acoustic performance of the modulators (noise generators) and representative 

horns that would be required to meet the desired spectra, as well as to evaluate possible supplemental gas jet noise sources. The knowledge 

obtained in each of these test programs enabled the design of the RATF sound generation system to confidently advance to its final acoustic 

design and subsequent ongoing construction. 

15. SUBJECT TERMS

Acoustics; Testing; Spacecraft qualification; Dynamics; Dynamic tests; Acoustic vibrations 

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