L. Danielle Koch, Clifford A. Brown, Tony D. Shook, James Winkel, and John S. Kolacz

Glenn Research Center, Cleveland, Ohio

Devin M. Podboy

Gilcrest, Inc., Macedonia, Ohio

Raymond A. Loew and Julius H. Mirecki

Sierra Lobo, Inc., Fremont, Ohio

Acoustic Measurements of an Uninstalled 

Spacecraft Cabin Ventilation Fan Prototype

NASA/TM—2012-217692

September 2012

12_158
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L. Danielle Koch, Clifford A. Brown, Tony D. Shook, James Winkel, and John S. Kolacz

Glenn Research Center, Cleveland, Ohio

Devin M. Podboy

Gilcrest, Inc., Macedonia, Ohio

Raymond A. Loew and Julius H. Mirecki

Sierra Lobo, Inc., Fremont, Ohio

Acoustic Measurements of an Uninstalled 

Spacecraft Cabin Ventilation Fan Prototype

NASA/TM—2012-217692

September 2012

12_158

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for

Inter-Noise 2012, The 41st International Congress and Exposition on Noise Control Engineering

sponsored by the Acoustical Society of America and Society of Automotive Engineers International

New York, New York, August 19–22, 2012
Acknowledgments

The authors thank Dan Sutliff for his guidance while acquiring data. We appreciate the expertise of Bridget Caswell and Mark 

Grills who photographed the fan and Richard Czentorycki who illustrated the experiment. We also are grateful to Chris Allen from 

NASA Johnson for acquiring funds for this research through NASA’s International Space Station Program.

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Trade names and trademarks are used in this report for identification 

only. Their usage does not constitute an official 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—2012-217692 1

Acoustic Measurements of an Uninstalled Spacecraft Cabin 

Ventilation Fan Prototype 

L. Danielle Koch, Clifford A. Brown, Tony D. Shook, James Winkel, and John S. Kolacz 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Devin M. Podboy 

Gilcrest, Inc. 

Macedonia, Ohio 44056 

Raymond A. Loew and Julius H. Mirecki 

Sierra Lobo, Inc. 

Fremont, Ohio 43420 

Abstract 

Sound pressure measurements were recorded for a prototype of a spacecraft cabin ventilation fan in a 

test in the NASA Glenn Acoustical Testing Laboratory. The axial fan is approximately 0.089 m (3.50 in.) 

in diameter and 0.223 m (9.00 in.) long and has nine rotor blades and eleven stator vanes. At design point 

of 12,000 rpm, the fan was predicted to produce a flow rate of 0.709 m3

/s (150 cfm) and a total pressure 

rise of 925 Pa (3.72 in. of water) at 12,000 rpm. While the fan was designed to be part of a ducted 

atmospheric revitalization system, no attempt was made to throttle the flow or simulate the installed 

configuration during this test. The fan was operated at six speeds from 6,000 to 13,500 rpm. A 13-

microphone traversing array was used to collect sound pressure measurements along two horizontal 

planes parallel to the flow direction, two vertical planes upstream of the fan inlet and two vertical planes 

downstream of the fan exhaust. Measurements indicate that sound at blade passing frequency harmonics 

contribute significantly to the overall audible noise produced by the fan at free delivery conditions. 

Introduction 

Quiet and efficient fans are needed if spacecraft for future long-duration human exploration missions 

are to be safe and productive. The Man-Systems Integration Standards report (Ref. 1) describes on-orbit 

noise sources and noise limits for the Space Shuttle Orbiter and continues to be used as a reference for new 

missions. Environmental control equipment and avionics equipment were identified as significant 

continuous sources of noise. Octave band spectra are presented for eight components (including three fans: a 

cabin fan, an avionics fan, and an intermodule unit (IMU) fan) on the Space Shuttle’s flight deck and mid 

deck. The cabin fan was proven to be the dominant source of noise among the measured components, 

exceeding recommended limits for both tone and broadband noise. The recommended limit for all 

broadband noise sources is Noise Criteria (NC) 50 and the recommended limit for all tones is the NC 40 

curve, which is 10 dB less than the broadband limit for the octave band containing the tone (Refs. 1 and 2). 

A new spacecraft cabin ventilation fan is currently being studied in an effort to identify sources of 

broadband and tone noise, and determine ways to improve aerodynamic and acoustic performance of the 

fan. Design point pressure rise and flow rate conditions were identified, and a working prototype of the 

fan has been produced by NASA. Reported here are the details of the aerodynamic, mechanical, and 

electrical design of the fan prototype. The prototype was operated for the first time in NASA Glenn’s 

Acoustical Testing Laboratory. No attempt was made to simulate the ducting or other ventilation system 

components during this test. Narrowband sound pressure level measurements for six fan speed settings 

indicate that tones at blade passing frequencies contribute significantly to the overall noise produced by 
NASA/TM—2012-217692 2

the fan operating at free delivery conditions. Further testing is required to determine design point 

aerodynamic and acoustic performance. 

Description of Prototype Design and Fabrication 

 Aerodynamic and Acoustic design 

Details of the aerodynamic design and results of an aerodynamic analysis have been reported in 

Reference 4. The overall design goals were to minimize weight, volume, power, and audible noise while 

maximizing aerodynamic efficiency of an axial fan nominally suited for a spacecraft ventilation system. 

The design point goals were established and are presented in Table 1, as well as the design and predicted 

values for the prototype. Efforts were made to minimize rotor rotational speed and select a blade/vane 

count that would minimize broadband and tone noise. 

A computational fluid dynamics (CFD) code was used iteratively to refine the input to a compressor 

design code used to develop the blade path, rotor blade shape, and stator vane shape shown in Figure 1. 

The acoustic theory of Tyler and Sofrin3

 indicated that by choosing either 11 or 22 stator vanes the first 

three blade passing harmonics tones would be cut-off if the fan were installed in an infinitely long duct. 

Mechanical Design and Fabrication 

The NASA Glenn Research Center’s Mechanical and Rotating Systems Branch was given the 

aerodynamic design of the fan described above and developed an electromechanical conceptual design. Details 

of the conceptual design study have been presented in Reference 5 and a cross section is shown in Figure 2. 

The conceptual design was advanced to a working prototype suitable for acoustic and aerodynamic 

ground tests. A cross-sectional view of the final prototype design is shown in Figure 4. Finite element 

analyses (FEA) using MSC Patran/Nastran were performed to refine the mechanical design, to determine 

candidate materials, and to ultimately verify that the final mechanical design and material choice would 

meet safety requirements. 

A stereolithography manufacturing technique was chosen because it fit the structural requirements, 

budget, and time constraints of the project. Two prototypes were fabricated by The Technology House, 

LTD. of Solon, Ohio. The material selected was the Huntsman RenShape SL5530 photopolymer. Selected 

material properties are shown in Table 2. The two fan prototypes differed only in the thickness of crosssection layers of liquid resin that are cured by a solid-state laser. Prototype A has layer thickness of 0.127 

mm (0.005 in.) and Prototype B has 0.051 mm (0.002 in.) layers for a smoother surface finish and 

increased dimensional accuracy. 

MSC Nastran was used to perform the rotor finite element stress analysis. Fan rotational speed was 

set to its design point value of 12,000 rpm and blade loads were neglected. Plots of the rotor stresses are 

shown in Figure 5. Maximum stress of 3.09×106

 Pa (448 psi) was located at the rotor bore where the rotor 

mates to the rotor shaft. The margin of safety for the current design is 4.05. 

Results of the rotor modal analysis are shown in the Campbell diagram of Figure 6. The modal 

analysis is used to identify the resonance frequencies of the rotor that could be excited during operation. 

The critical speeds of the fan rotor are indicated in Table 3. In order to prevent damage to the fan, 

prolonged operation at these critical speeds should be avoided. 

The fan would be damaged if the rotor blade tips rubbed against the shroud during operation. Finite 

element analysis was used to predict maximum blade/hub displacements at design speed. The predicted 

rotor blade/hub displacement was 0.0254 mm (0.001 in.) at 12,000 rpm-significantly less that the 

0.254 mm (0.010 in.) rotor tip gap. 

Finally, in order to minimize the weight of the final prototype design to make it geometrically resemble 

a fan for a spaceflight ventilation system, material was removed from the duct wall in a grid-like pattern as 

shown in Figure 3. Minimum duct wall thickness of the final design was chosen to be 0.318 cm (0.125 in.) 

in order to maintain fan-housing stiffness and contain fragments of the rotor should it fail during operation. 
NASA/TM—2012-217692 3

Flange thicknesses were reduced, and excess material between flange boltholes was removed. Additionally, 

a flow straightener was installed in the fan inlet from metal honeycomb that was 2.54 cm (1.00 in.) thick 

with 0.476 cm (0.188 in.) square cells and a foil thickness of 0.076 mm (0.003 in.). 

Electrical Design 

The design team chose a brushless DC motor, Maxon EC-4 pole 305015, for several reasons. This 

motor was chosen since it met the torque and speed requirements of the fan, and its availability and cost fit 

within project constraints. The motor diameter was 30.0 mm (1.18 in.) and the motor length was 99.0 mm 

(3.90 in.)—small enough to fit well within the fan centerbody. The wiring exited the motor through the aft 

end face. This was important since the motor wiring was to be routed through one of three hollow support 

struts placed as far downstream of the fan rotor as practically possible in an effort to minimize rotor/strut 

interaction noise without exceeding the maximum desired overall axial length of the fan. 

The fan motor speed controller consisted of a brushless servo amplifier and ancillary support 

circuitry. The servo amplifier drives the motor rotation by providing current pulses to the fan motor. The 

frequency of the current pulses establishes the fan motor speed. The servo amplifier has an external 

analog input for setting the speed. A digital potentiometer configured as a voltage divider is attached to 

the analog input. The fan motor with the fan attached was run at various potentiometer settings and the 

fan speed was measured with an optical tachometer. A look-up table was created with this data for setting 

the fan speed for testing. For safety purposes, an emergency stop relay circuit was used to enable and 

disable the servo amplifier to control fan rotation. 

Description of Experiment 

Facility 

The NASA Glenn Acoustical Testing Laboratory (ATL) (Ref. 6), illustrated in Figure 7 is a fully 

anechoic chamber with interior dimensions of 7.0- by 5.2- by 5.2-m (23- by 17- by 17-ft). The walls, 

ceiling, and floor of the chamber are completely covered with fiberglass wedges that are 0.86 m (34 in.) 

deep. The wedges are designed to absorb 99 percent of all sound above 100 Hz. Dense rubber material in 

the walls and ceiling reflects and absorbs ambient sound coming from outside the chamber. A separate 

control room, located adjacent to the chamber, houses all of the electronic equipment as well as the test 

operators. Steel grating is mounted over the floor wedges to allow personnel to walk throughout the 

chamber but still allow sound to pass through to the wedges below. Half of these grates were removed for 

this test in order to mitigate sound reflections as much as possible. 

 Four stationary condenser microphones were located in each corner of the test chamber at 3.04 m 

(10.0 ft) from the fan, as shown in Figure 7. Figure 8 shows a photograph of the microphone array used to 

acquire the acoustic data presented in this report. The array consists of 13 condenser microphones spaced 

7.6 cm (3.0 in.) apart. As shown in the figure, the microphones pointed downward and were arranged 

horizontally in a line so that they were all the same distance from the floor. An overhead three-axis 

traverse was used to remotely position the microphone array relative to the test article. Each axis of the 

traverse is powered separately by its own electric motor and provides positioning accuracy of ± 0.03 mm 

(± 0.001 in.). A series of concentric tubing to allow the array is manually adjusted to position the array at 

the desired location along the vertical z-axis. The maximum travel distances provided by the x, y, and z 

axes were 4.85 m (15.9 ft), 3.41 m (11.2 ft), and 4.27 m (14.0 ft), respectively. 

Instrumentation 

The signals from the thirteen Brüel & Kjær Falcon 4939 0.64 cm (0.25 in.) condenser microphones and 

the four stationary microphones were input to a Larson-Davis model PRM902 1.3 cm (0.50 in.) preamplifier, 

using a Brüel & Kjær UA0035 adapter. A Brüel & Kjaer Nexus 2690 conditioning amplifier powered all 
NASA/TM—2012-217692 4

microphones. A Precision Filters, Inc. high pass filter, set to 200 Hz, filtered the microphone signals. The 

amplified and filtered signal was then recorded by a DataMax DTX-9R data acquisition computer. 

The temperature, atmospheric pressure, and humidity inside the chamber were monitored by a Vaisala 

PTU 303 transmitter. One chromel-alumel type K thermocouple was attached to the fan motor housing 

and monitored using an Altek 422 meter. An Endevco 2221 D accelerometer was mounted to one of the 

unused fan exhaust flange boltholes and measured the vibrations in the axial direction. Accelerometer 

measurements were displayed in the control room with an Endevco 6634B charge amplifier/digital 

display. Finally, a Keyence FU-35FA/FS-M1H fiber optic sensor monitored the speed of the rotor. The 

signal from the sensor was converted to revolutions per minute (rpm) using a Newport INF7 digital 

display. The data acquisition computer also recorded the speed signal. 

Procedure 

There were several objectives of this experiment. The first objective was to run the fan prototype to 

determine if it operated mechanically and electrically as expected. The second objective was to collect 

sound pressure measurements using the traversing microphone array for six fan speed settings. 

Figure 9 is a diagram that shows the location of the microphone survey planes for this experiment. 

The spacecraft vent fan prototype was mounted in the center of the anechoic chamber 140.3 cm 

(55.25 in.) above the floor grating. An x-y-z coordinate system was used to describe the location of the 

microphone array relative to the fan. The origin of the coordinate system was located along the axis and 

in the inlet plane of the fan. The microphone located at the center of the array served as the reference. The 

distance between the center microphone and the origin in each of the three coordinate directions was used 

to describe the location of the array relative to the fan. The microphone measurement positions are 

described in Table 4. 

The test procedure was as follows: a) set fan test speed, b) record fan speed, ambient pressure, 

temperature, humidity, fan casing vibration level, and motor housing temperature, and c) move the 

microphone array to desired measurement positions and record sound pressures for 10 sec at each 

measurement position using a 200 kHz sampling rate. The tested fan speed settings and corresponding 

blade passing frequencies are listed in Table 5. 

Discussion of Results 

The fan performed mechanically and electrically as expected. The motor was not actively cooled; 

rather, the three hollow support struts downstream of the fan vanes vented the enclosed area around the 

fan. Motor housing temperatures did not exceed 337 K (147 °F), well below the recommended limit for 

continuous operation of 350 K (170°F). No mechanical difficulties were experienced during the 40 hr of 

operation. Vibration levels in the axial direction did not exceed 1.5 mm/s (0.06 in./sec). 

Measurements from the microphone at the center of the rake are presented in Figures 10 and 11. 

Figure 10 compares the narrowband spectra from a single microphone located downstream and above the 

fan, stopped at one point in the Survey Number 4 (x = 39.00 in., y = 0.00 in., z = 40.75 in.). This point 

was chosen since blade passing frequency harmonics were maximized at this location for the design point 

speed of 12,000 rpm. Figure 11 compares contour plots of frequency as a function of axial location for all 

tested fan speeds. 

Both Figure 10 and 11 indicate that the highest sound pressure levels measured were those at blade 

passing frequency harmonics, and are thus associated with the aerodynamic design of the fan. The reader 

is reminded that the fan was designed to operate in a ducted system, and that inlet and exhaust ducting 

was not included in this initial test of the fan. So while the fan was operated at design speed, it was not 

operating at design pressure rise and flow rate conditions during this experiment. It is hypothesized that 

by mimicking the ventilation system by installing ducting upstream and downstream of the fan, tone noise 

at the first three harmonics of the blade passing frequency can be significantly reduced by taking 

advantage of the cut-off phenomenon. Additionally, tones expect to propagate are hypothesized to 
NASA/TM—2012-217692 5

decrease as the wakes from the rotor blades narrow when the fan operates at design conditions. Additional 

aerodynamic and acoustic tests are required to test these hypotheses. 

The plots in Figure 11 exhibit the acoustic radiation patterns similar to those of aircraft engine fans 

with sound pressure level minima occurring halfway between the inlet and the exhaust, a trend that is 

independent of the fan speed. There appear to be faint “ripples” in the sound pressure level contours if 

one closely examines Figure 11, most visible in Figure 11b and Figure 11c for frequencies above 10 kHz, 

but present at all speeds and all frequencies. The nature of these ripples is not known but is currently 

thought to be associated with the electromechanical performance of the microphone traverse system, 

though further tests are needed to confirm this. 

The tones measured from 20 to 35 kHz are attributed to the motor. Limits on the amplitude of 

ultrasonic tones are given in Reference 1. The measurements indicate that for the conditions tested the fan 

does not exceed the recommended limits for ultrasonic noise (105 to 115 dB for the measured frequency 

range). And while humans would not be affected by the ultrasonic tones produced by the fan motor, the 

ultrasonic tones are well within the audible range for many animals and could influence any onboard 

animal experiments (Refs. 7 and 8). The motor is also considered to be a source of audible broadband 

noise. Audible broadband noise from the motor was observed (but not measured) when the motor was 

operated alone prior to assembly of the fan. 

Conclusions and Recommendations 

A prototype of a ventilation fan notionally suited for a spacecraft cabin ventilation system has been 

fabricated. An initial test of the mechanical, electrical, and acoustic performance of the fan has been 

conducted in the NASA Glenn Acoustical Testing Laboratory. Results indicated that the fan prototype 

performed mechanically and electrically as expected. The fan was tested without ducting upstream or 

downstream, as would be present in typical spacecraft ventilation systems. The fan was operated at six 

speed settings ranging from 6,000 to 13,500 rpm. Acoustic measurements were recorded using a thirteenmicrophone traversing array. A limited examination of the acoustic data from a single microphone 

indicated that tones at blade passing frequency and its harmonics were dominant and is associated with 

the aerodynamic design of the fan. The motor was observed to be a source of broadband noise, and 

considered to be the source of ultrasonic tones. 

Several recommendations are suggested at this time: 

a) Efforts should be made to either identify a motor speed encoder suitable for the operational speed 

range of the motor that will fit on the aft end of the motor shaft or to relocate the optical sensor to the aft 

end of the fan. For this test, a hole was drilled into the inlet duct to hold the optical speed sensor. The 

rotor hub was painted black, and white tape was attached to the rotor hub. While this arrangement did 

produce a reliable speed measurement, the modifications to the duct could be a source of noise and the 

tape affixed to the rotor could be a source of imbalance resulting in structure-borne noise. 

b) Efforts could be made to identify different motor control designs to try to minimize the audible 

noise produced by the motor. 

c) Efforts could be made to identify different ways to attach the rotor hub to the motor shaft. In this 

prototype, the rotor was glued to the motor shaft. This type of attachment makes it difficult to disassemble 

if different stator concepts are to be investigated. 

d) A speed feedback loop in the motor controller may be useful in maintaining the fan at constant 

speed settings, something that may be desirable in future aerodynamic and acoustic tests that involve 

backpressuring the fan. 

e) Additional analyses and structural tests are needed to determine if the operational speed range of 

the fan can be safely extended. 

f) The aerodynamic performance of the fan should be experimentally measured for a range of fan 

speeds and flow rates. 

g) Acoustic measurements with the fan backpressured to design point conditions are needed. 
NASA/TM—2012-217692 6

h) Once more is known about the fan’s aerodynamic and acoustic performance at design point 

conditions, investigations to further improve the fan could be conducted. 

References 

1. Christensen, J. M., McBarron, J. W., McConville, J. T., Pogue, W. R., Williges, R. C., Woodson, W. 

E., "Man-Systems Integration Standards--Vol. I," NASA-STD-3000 Vol. 1, (1995). 

2. Ver, Istvan L., Beranek, Leo L., Noise and Vibration Control Engineering, Principles and 

Applications, Second Edition, John Wiley & Sons, Inc., (2006). 

3. Tyler, J. M. and Sofrin, T. G., "Axial Flow Compressor Noise Studies," SAE Transactions, 70, 309-

332, (1962). 

4. Tweedt, D. L., "Aerodynamic Design and Computational Analysis of a Spaceflight Vehicle Cabin 

Ventilation Fan," NASA TM-2010-216329, (2009). 

5. Koch, L. D., "Tone noise predictions for a spacecraft cabin ventilation fan ingesting distorted inflow 

and the challenges of validation," Proceedings of NoiseCon 2011, (2011). 

6. Cooper, B. A., "Design and Construction of a Convertible Hemi-Anechoic Acoustical Laboratory for 

Testing Space Flight Hardware at the NASA Glenn Research Center," Proceedings of NoiseCon 

2000, (2000). 

7. Heffner, Henry E., Heffner, Rickye S., "Hearing," in Comparative Psychology: A Handbook, ed. 

Gary Greenberg and Maury M. Haraway, Garland Publishing, Inc., New York, (1998). 

8. Fay, R. R., Hearing in Vertebrates: A Psychophysics Databook, Hill-Fay Associates, Winnetka, IL, 

(1988). 

TABLE 1.—SPACECRAFT CABIN FAN DESIGN POINT GOALS AND DESIGN/PREDICTED VALUES 

 Goals Predicted/Model Value 

Flow rate 0.709 m3/s (150.3 cfm) 0.709 m3/s (150.3 cfm) 

Total pressure rise 906 Pa (3.64 in. of water) 925 Pa (3.716 in. of water) 

Pressure 101 kPa (14.7 psia) 101 kPa (14.7 psia) 

Temperature 21.1 °C (70 °F) 21.1 °C (70 °F) 

Maximum diameter 0.102 m (4.0 in.) 0.089 m (3.5 in.) flowpath diameter 

Maximum axial length 0.223 m (9.0 in.) 0.223 m (9.0 in.) 

Rotor tip clearance gap 0.23 mm (0.009 in.) 0.23 mm (0.009 in.) 

Rotor speed Unconstrained 12,000 rpm 

Number of blades Unconstrained 9 

Number of vanes Unconstrained 11 

TABLE 2.—SELECTED PROPERTIES OF SL5530 MATERIAL 

Mechanical Properties 

Tensile Strength (ASTM D 638) 4.69×107

 – 6.14×107 Pa (6,800 to 8,900 psi) 

Elongation at Break 1.3 – 2.9% 

Flexural Modulus (ASTM D 790) 3.50×109

 – 3.63×109 Pa (507 to 527 ksi) 

Flexural Strength (ASTM D 790) 9.58×107

 – 1.08×108 Pa (13,900 to 15,700 psi) 

Thermal Properties 

Heat Deflection Temp (at 66 psi) 443 to 523 K (338 to 482 °F) 

Heat Deflection Temp (at 264 psi) 383 to 393 K (230 to 248 °F) 

Description 

Color Appearance Clear Amber 

Hardness 90 D 

Application High Heat 
NASA/TM—2012-217692 7

TABLE 3.—PREDICTED CRITICAL SPEEDS OF THE ROTOR 

4E 11E 22E 

11,350 rpm (Mode 1) 4,050 rpm (Mode 1) 2,025 rpm (Mode 1) 

5,650 rpm (Mode 2) 2,800 rpm (Mode 2) 

11,200 rpm (Mode 3) 3,600 rpm (Mode 3) 

11,450 rpm (Mode 4) 

 12,050 rpm (Mode 5) 

 TABLE 4.—DESCRIPTION OF MICROPHONE SURVEYS 

X locations, 

in. 

Y locations, 

in. 

Z locations, 

in. 

Survey 

Number 

Survey Plane 

Orientation 

Number of 

steps 

Start Step size Start Step size Start Step size 

0 Point 1 –84.00 0.00 0.00 0.00 56.45 0.00 

1 Horizontal 57 –84.00 3.00 0.00 0.00 56.45 0.00 

2 Horizontal 29 –84.00 6.00 –33.00 0.00 56.45 0.00 

3 Horizontal 29 –84.00 6.00 33.00 0.00 40.75 0.00 

4 Horizontal 57 –84.00 3.00 0.00 0.00 40.75 0.00 

5 Horizontal 29 84.00 –6.00 –33.00 0.00 40.75 0.00 

6 Horizontal 29 84.00 –6.00 33.00 0.00 56.45 0.00 

7 Vertical, inlet 28 –72.00 0.00 0.00 0.00 56.45 –3.00 

8 Vertical, inlet 14 –72.00 0.00 –33.00 0.00 56.45 –6.00 

9 Vertical, inlet 14 –72.00 0.00 33.00 0.00 56.45 –6.00 

10 Vertical, exit 14 72.00 0.00 0.00 0.00 56.45 –3.00 

11 Vertical, exit 7 72.00 0.00 –33.00 0.00 56.45 –6.00 

12 Vertical, exit 7 72.00 0.00 33.00 0.00 56.45 –6.00 

13 Vertical, inlet 28 –36.00 0.00 0.00 0.00 56.45 –3.00 

14 Vertical, inlet 14 –36.00 0.00 –33.00 0.00 56.45 –6.00 

15 Vertical, inlet 14 –36.00 0.00 33.00 0.00 56.45 –6.00 

16 Vertical, exit 14 36.00 0.00 0.00 0.00 56.45 –3.00 

17 Vertical, exit 7 36.00 0.00 –33.00 0.00 56.45 –6.00 

18 Vertical, exit 7 36.00 0.00 33.00 0.00 56.45 –6.00 

 

TABLE 5.—TEST CONDITIONS 

Speed (rpm) 6000 7000 8500 11000 12000 13500 

Speed (Hz) 100 117 142 183 200 225 

Blade passing frequency (Hz) 900 1,050 1,275 1,650 1,800 2,025 

Wavelength of BPF tone (m) 0.38 0.32 0.27 0.21 0.19 0.17 

Max audible BPF harmonic 22 19 15 12 11 9 
NASA/TM—2012-217692 8

 

Figure 1.—Aerodynamic Design of Spacecraft Cabin 

Ventilation Fan Prototype Figure 2.—Conceptual Electromechanical Design of Spacecraft 

Cabin Ventilation Fan Prototype 

Figure 4.—Final Design of Spacecraft Cabin Ventilation 

Fan Prototype 

Figure 3.—Final Design of Spacecraft Cabin Ventilation 

Fan Prototype showing surface pocketing for weight 

reduction 
NASA/TM—2012-217692 9

Figure 5.—Rotor stress analysis results for final design of spacecraft cabin ventilation fan prototype 

Figure 6.—Campbell diagram for final design of spacecraft cabin ventilation fan prototype 
NASA/TM—2012-217692 10

CD-12-83321

Figure 7.—The spacecraft cabin ventilation fan prototype in the NASA Glenn Acoustical Testing Laboratory
NASA/TM—2012-217692 11

Figure 8.—Photograph of spacecraft cabin ventilation fan prototype and 

traversing microphone array in the NASA Glenn Acoustical Testing 

Laboratory 

Figure 9.—Microphone survey planes are shown in solid black lines. 
NASA/TM—2012-217692 12

Figure 10.—Narrowband sound pressure levels are plotted as a function of narrowband center frequencies for all tested 

fan speeds. Measurements are from a single microphone located at the center of the traversing array. Test day 

conditions, instrument corrected values are plotted. 
NASA/TM—2012-217692 13

Figure 11.—Narrowband sound pressure level contours are plotted as for all tested fan speeds. Measurements are from a 

single microphone moved axially from upstream of the fan downstream. The y and z position of the microphone was constant 

for this survey (y=0.00 in, z= 40.75 in). Test day conditions, instrument corrected values are plotted.
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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 

1. REPORT DATE (DD-MM-YYYY)

01-09-2012 

2. REPORT TYPE

Technical Memorandum 

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Acoustic Measurements of an Uninstalled Spacecraft Cabin Ventilation Fan Prototype 

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S)

Koch, L., Danielle; Brown, Clifford, A.; Shook, Tony, D.; Winkel, James; Kolacz, John, S.; 

Podboy, Devin, M.; Loew, Raymond, A.; Mirecki, Julius, H. 

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

WBS 067463.01.01.03 

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

John H. Glenn Research Center at Lewis Field 

Cleveland, Ohio 44135-3191 

8. PERFORMING ORGANIZATION

 REPORT NUMBER

E-18375 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration 

Washington, DC 20546-0001 

10. SPONSORING/MONITOR'S

 ACRONYM(S)

NASA 

11. SPONSORING/MONITORING

 REPORT NUMBER

NASA/TM-2012-217692 

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified-Unlimited 

Subject Categories: 02 and 71 

Available electronically at http://www.sti.nasa.gov 

This publication is available from the NASA Center for AeroSpace Information, 443-757-5802

13. SUPPLEMENTARY NOTES

14. ABSTRACT

Sound pressure measurements were recorded for a prototype of a spacecraft cabin ventilation fan in a test in the NASA Glenn Acoustical 

Testing Laboratory. The axial fan is approximately 0.089 m (3.50 in.) in diameter and 0.223 m (9.00 in.) long and has nine rotor blades and 

eleven stator vanes. At design point of 12,000 rpm, the fan was predicted to produce a flow rate of 0.709 m3/s (150 cfm) and a total pressure 

rise of 925 Pa (3.72 in. of water) at 12,000 rpm. While the fan was designed to be part of a ducted atmospheric revitalization system, no 

attempt was made to throttle the flow or simulate the installed configuration during this test. The fan was operated at six speeds from 6,000 

to 13,500 rpm. A 13-microphone traversing array was used to collect sound pressure measurements along two horizontal planes parallel to 

the flow direction, two vertical planes upstream of the fan inlet and two vertical planes downstream of the fan exhaust. Measurements 

indicate that sound at blade passing frequency harmonics contribute significantly to the overall audible noise produced by the fan at free 

delivery conditions. 

15. SUBJECT TERMS

Fans; Noise 

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

 ABSTRACT

UU 

18. NUMBER

 OF 

 PAGES

20 

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email:help@sti.nasa.gov) 

a. REPORT

U 

b. ABSTRACT

U 

c. THIS 

PAGE

U 

19b. TELEPHONE NUMBER (include area code)

443-757-5802 

Standard Form 298 (Rev. 8-98)

Prescribed by ANSI Std. Z39-18