Ricardo A. Burdisso and Wing F. Ng

Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Fan Noise Control Using

Herschel-Quincke Resonators

NASA/CR—2003-212097

January 2003
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Ricardo A. Burdisso and Wing F. Ng

Virginia Polytechnic Institute and State University, Blacksburg, Virginia

Fan Noise Control Using

Herschel-Quincke Resonators

NASA/CR—2003-212097

January 2003

National Aeronautics and

Space Administration

Glenn Research Center

Prepared under Grant NAG3–2694
Available from

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

National Technical Information Service

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This report is a formal draft or working

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ideas from a technical peer group.

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findings, subject to revision as

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The Propulsion and Power Program at

NASA Glenn Research Center sponsored this work.

Available electronically at http://gltrs.grc.nasa.gov
TABLE OF CONTENTS 

1.

2.

2.1.

2.2.

a.

b.

2.3.

2.4.

2.5.

2.6.

2.7.

3.

4.

NASA/CR—2003-212097 iii

PROGRAM GOALS_________________________________________________ 1

TASK PERFORMED DURING FY02 __________________________________ 2

Define ANCF rig configurations ________________________________________ 3

Design Inlet HQ-Liner-system _________________________________________ 3

Liner Design and Performance __________________________________________________ 4

Fabrication spool-piece for inlet HQ-liner system ________________________ 9

HQ-system Design and Performance _____________________________________________ 6

Test inlet HQ-Liner-system ___________________________________________ 11

Data reduction and analysis __________________________________________ 12

Develop model for aft HQ-Liner-system ________________________________ 12

Design Aft HQ-Liner-system __________________________________________ 14

ACCOMPLISHEMENTS DURING FY02 ______________________________ 14

REFERENCES ___________________________________________________ 15

1. PROGRAM GOALS 

The research effort proposed for this NASA NRA [1] is mainly experimental. In 

addition, Virginia Tech is working in partnership with Goodrich Aerospace, 

Aerostructures Group for the analytical development needed to support the experimental 

endeavor, i.e. model development, design, and system studies. 

In this project, HQ-liner technology experiments will be performed at the NASA 

Glenn Active Noise Control Fan (ANCF) facility. Figure 1 shows a schematic of both 

inlet and aft HQ-liner systems installed in the ANCF rig as well as a picture of the Glenn 

facility. As shown, the main goal is to simultaneously test in both the inlet and bypass 

duct sections. The by-pass duct will have HQ-systems in both the inner and outer duct 

walls. The main advantages of performing tests at the ANCF facility are that the effect of 

the inlet HQ-system on the by-pass HQ-system and vice versa, can be accurately 

determined from the in-duct modal data. Another significant advantage is that it offers the 

opportunity to assess (on a common basis) the proposed noise reduction concept on the 

ANCF rig which in the past has been used for assessing other active and passive noise 

reduction strategies. 

Figure 1: (a) Schematic of complete proposed experiments on the (b) NASA Glenn 

ANCF rig. 

The main goals of the project are as follows: 

• To extend the application of the HQ-waveguide approach to the control of aft fan 

noise: In the last few years, the HQ-waveguide resonator technology has been 

successfully applied to inlet fan noise reduction from turbofan engines [2,-5]. These 

efforts involved testing in small turbofan engines as well as state-of-the-art engine 

inlet simulation facility simulating large bypass turbofan engines. Thus, this project 

will extend this technology to the control of aft radiated fan noise.

• To develop the model for the aft HQ system in conjunction with liners: Models of 

the HQ technology applied to the inlet duct have been previously developed by 

Inlet Mic. Rake 

ICD Fan 

Aft Mic. Rake

Vane

Inlet HQ-system Aft HQ-liner system 

Liner

(b) (a) 

NASA/CR—2003-212097 1
Virginia Tech under NASA and Goodrich support. Thus, a model for the HQ applied 

to the aft duct will be developed. The difference between the inlet duct and the aft 

duct is that in the aft section, the HQ can also be applied to the inner wall, i.e. the 

center body.

• To investigate the simultaneous implementation of the HQ-system to the inlet and 

aft ducts: The experiments on this project will allow to determine the performance of 

simultaneously implementing HQ-liner systems in both the inlet and aft ducts to 

control fan noise. 

• To validate the HQ-liner models: The analytical model developed for predicting the 

attenuation of the HQ-system is based on the assumption of knowledge of the fan 

complex modal amplitudes, i.e. magnitude and phase. Though numerical tools are 

available to predict these disturbance amplitudes for the tonal components, the 

accurate measurement of the inlet modal amplitudes in the ANCF rig makes these 

experiments ideal for the validation of the modeling approach. 

To accomplish these goals, three set of experiments will be performed at the ANCF rig. 

The first experiment consists of testing a HQ-liner system tested in the inlet of the ANCF 

rig as shown in Figure 2. These experiments will assess the effect of the inlet HQ-tube 

system on the resulting sound field in the by-pass duct. This will be accomplished by 

comparing modal measurements with and without an inlet HQ-system. Note that in these 

experiments there is no aft HQ-system implemented. This first set of experiments is 

planned to take place during November-December 2002 (FY02). 

Figure 2: Experimental setup using an inlet HQ-liner system to be tested 

Nov.-Dec. 02 (FY02). 

2. TASK PERFORMED DURING FY02 

In this section, the tasks performed during FY02 on this project are described in 

detail. 

Inlet Mic. Rake Aft Mic. Rake

Inlet HQ-systems 

Liner

NASA/CR—2003-212097 2
2.1. Define ANCF rig configurations

The first step in this project was to define the configuration to be tested at the ANCF rig. 

This task was performed in cooperation with NASA Glenn personnel to identify the most 

relevant fan modal structure to be tested. The ANCF fan configuration selected is 

described in Table I. This fan configuration has been previously used for active noise 

control experiments. 

Table I: Test configuration for ANCF test. 

Parameter Value 

Number of Blades 16 

Number of Vanes 28 

Design speed 1800 RPM 

Range of testing speeds 1400 – 1900 RPM 

Since the 2 blade-passage-frequency (2BPF) tone is the main noise fan component sought 

to be minimized, the sound power of the modes generated at the 2BPF at presented in 

Table II for both the inlet and aft ducts. 

Table II: Modal sound power at 2BPF tone due to Rotor-Vane Interaction – 1800 rpm. 

Inlet Duct Bypass Duct

Modes Power

dB 

Modes Power

dB 

(4,0) 106.1 (4,0) 110.2 

(4,1) 107.0 (4,1) 101.2 

Total 109.6 Total 110.7

Note that the rotor-vane interaction is cut-off at BPF tone. It is also important to remark 

that at ~ 1500 RPM the (4,1) mode is cut-on in both inlet and exhaust ducts. This will 

allow investigating the performance of the HQ-system for modes that are just after cut-on 

that radiates towards the side lines. Previous work on the JT15D engine has shown very 

good attenuation of these modes. 

2.2. Design Inlet HQ-Liner-system: 

Two inlet HQ-systems were designed for the ANCF rig configurations selected in the 

previous task. The first design assumed the HQ-resonators were mounted on a hard 

walled inlet while the second considered the HQ system to be integrated with a liner. The 

design of the HQ-system was performed by Virginia Tech personnel using a Goodrich 

“proprietary” analytical model (developed under a current Goodrich sponsored project 

NASA/CR—2003-212097 3
[6]). For this design task, the fan tonal modal amplitudes previously measured on the 

ANCF rig were used. 

The criterion to design the HQ-liner systems was based on the concept that the HQsystem should complement the liner’s attenuation. Since liners are mostly used as 

broadband attenuators, it was decided that the liner should be designed to reduce both 

broadband and the 3BPF, 4BPF and 5BPF tonal noise components. The HQ system was 

then designed to attenuate the 2BPF tone and potentially provide additional broadband 

reduction, in particular around and below the 2BPF tone. Figure 3 illustrates this HQliner design approach. 

Figure 3: Approach for the design of the HQ-liner systems. The liner was designed for 

attenuation of the broadband component and 3BPF, 4BPF, and 5BPF tone. HQ resonators 

designed to reduce 2BPF tone and broadband. 

a. Liner Design and Performance 

The liner was designed by Goodrich personnel. The liner selected was a “linear” liner of 

0.85” core depth. The normalized acoustic admittance of the liner implemented on the 

inlet of the ANCF rig is shown in Figure 4. Note the relatively high resistance of this 

liner (~ 1.7 ρc). 

0 1000 2000 3000 4000

Frequency [Hz]

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105

Sound P

o

wer Level [d

B-ref. 10-12 Watts]

BPF

2 BPF

3 BPF 4 BPF

5 BPF

Attenuated by HQ

Attenuated by Liner

NASA/CR—2003-212097 4
-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 2000 4000 6000 8000 10000

Frequency [Hz]

Normaliz

ed Ad

mitta

n

ce

Real

Imag

Figure 4: Normalized liner admittance assumed implemented on inlet. 

ANCF rig at 1800 rpm – Inlet flow speed M=0.11. 

Because the same liner will be used in the by-pass duct, the liner property was also 

computed (again by Goodrich personnel) assuming it is installed in the aft section. 

Figure 5 shows the normalized admittance. Note that the resistance of the liner installed 

in the bypass duct is lower (~1.4 ρc) that in the inlet. 

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 2000 4000 6000 8000 10000

Frequency [Hz]

N

ormalized Ad

mitta

n

ce

Real

Imag

Figure 5: Normalized liner admittance assumed implemented on bypass. 

ANCF rig at 1800 rpm – Aft duct flow speed M=0.15. 

The liner is currently been fabricated by Goodrich with an expected completion at the end 

of October 2002. 

NASA/CR—2003-212097 5
(m=0,1,...24) and 25 radial (μ=0,1,...24) mode orders for both positive and negative 

propagating modes were computed at small frequency steps. This information is required 

for the design of the HQ-waveguide system. 

The expected sound power attenuation of the liner installed in the inlet was determined 

assuming a liner length of 16”. The predictions were performed separately for the 

broadband and tonal components. For the broadband component, the equal energy 

approach was implemented. For the BPF, 2BPF, and 3BPF tones, the actual hard wall 

modal amplitudes (measured using the rotating rake system by personnel at NASA 

Glenn) were used in the predictions. The results are presented in Figure 6 which shows 

the sound power spectrum for the hard wall (HW) and lined duct cases. Sound power 

spectrum for hard wall was estimated from far-field microphone spectra (measured by 

personnel at NASA Glenn). The results show that the liner is very effective for 

frequencies > 1200 Hz, i.e. frequencies above the 2BPF tone. The inlet liner broadband 

attenuation is about 3-5 dB at frequencies > 1200 Hz. The liner attenuated the 2BPF tone 

by ~ 6 dB. 

Figure 6: Sound power level spectrum for the inlet duct – Hard wall and liner. 

b. HQ-system Design and Performance 

The HQ-system for the inlet was next investigated. The design of the HQ system was first 

carried out assuming a hard-wall inlet duct. The HQ-system was designed for maximum 

attenuation of the 2BPF tone at 1800 rpm, i.e. 2BPF frequency = 960 Hz. The measured 

hard wall duct modal amplitudes (using the rotating rake) were used in the design, i.e. 

(4,0) and (4,1) modes. The main parameters of the HQ-systems are described in Table III. 

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0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Frequency [Hz]

Sound Power Level [dB- ref. 10-12 watts]

Inlet Power - HW

Inlet Power - Liner

BPF

2 BPF

3 BPF

4 BPF

Using the liner properties shown in Figures 4 and 5, the inlet and bypass duct 

eigenproblems were solved. The acoustic mode properties for the first 25 circumferential 

NASA/CR—2003-212097 6
Table III: Main HQ-system parameters for Hard wall and lined inlet. 

Parameter Hard Wall Inlet Lined Inlet 

Number of arrays 2 2 

Number of HQ-tubes in each 

array 

24 24 

Configuration Staggered Staggered 

HQ-tube length, L 12” 12” 

HQ-tube interface distance, l 7.62” (0.193 m) 5.9” (0.15 m) 

HQ-tube area (each) 7.56 in2 7.56 in2

Surface liner area ratio -- 0.3 

Cross sectional area ratio 0.1 0.1 

In this table, two area ratio parameters are defined: 

(a) Cross sectional area ratio = (HQ-tube cross section area)*number of tubes in array

Inlet cross sectional area

(b) Surface liner area ratio = (HQ-tube cross section area)*2*total number of tubes

Liner surface area

From experience, the first parameter is normally selected to be as high as possible within 

practical limitation. Previous experiments at Virginia Tech and other facilities, this area 

ratio has been ~ 0.1. The second parameter indicates how much of the available liner 

surface treatment is “taken” by the HQ-system. The two arrays of HQ tubes are “taken” 

about 30% of the liner surface. Figure 7 shows the HQ-design for hard wall condition. 

Note that the HQ-waveguide will be mounted on the back of the liner. Thus, the core of 

the liner forms part of the HQ-waveguide. The hard wall condition will be simulated by 

taping the “wet” side of the liner. 

 

Figure 7: HQ-waveguide mounted on the back of the liner. 

The predicted attenuation for the HQ-system is presented next. Figures 8a and 8b shows 

the sound power attenuation due to the HQ-system for the 2BPF tone at 960 Hz (fan at 

1800 rpm) as a function of the tube length L and interface distance  for hard and soft 

wall conditions, respectively. In both figures, the optimum HQ parameters are indicated. 

It can be observed that the HQ system when used in conjunction with the liner performs 

L HQ Area

0.85”

HQ-Waveguide

 Line

Side View Top View



NASA/CR—2003-212097 7
much better than when used on a hard wall inlet, i.e. 6.14 dB for the HQ-liner as 

compared to 3.37 for the HQ-hard wall case. This will be further investigated to 

determine the physical mechanism for the improvement in performance. The figures also 

show that, within reasonable range, the HQ performance does not seem to be very 

sensitive to the tube parameters for either case. 

To investigate the overall performance of the inlet HQ-liner system, figure 9 shows the 

sound power spectra for the hard wall (HW) case and for the HQ-liner system. 

Comparing the result in Figure 9 (HQ-liner) to Figure 6 (Liner), the HQ system resulted 

in an additional 2BPF tone reduction of 6 dB as well as an increase of the broadband 

attenuation (~ 1.0 to 1.5 dB) at frequencies > 700 Hz. If confirmed experimentally, the 

results will validate the potential of the HQ-liner system to be used in conjunction with 

liner to reduce fan noise. 

Figure 8: Sound power attenuation of the 2BPF tone as a function of the tube length L 

and interface distance: (a) hard wall and (b) soft wall. 

Fan at 1800 rpm for a 2BPF tone at 960 Hz 

NOTE: the color bar codes are for different ranges. 

(a) (b) 

NASA/CR—2003-212097 8
Figure 9: Inlet sound power spectra for hard wall and HQ-liner system. 

Fan at 1800 rpm. 

2.3. Fabrication of spool-piece for inlet HQ-liner system: 

A spool section for the inlet of the ANCF rig was fabricated to implement the HQ-liner 

system. The spool piece structure was made in two halves to also allow its 

implementation on the bypass duct of the ANCF rig. The integration of the liner and the 

supporting structure is illustrated in Figure 10. The liner (also made in two halves) will be 

bonded to the two aluminum supporting rings and the beams connecting the rings. Figure 

11 shows a picture of the liner supporting structure (without liner installed). This 

structure was fabricated by Virginia Tech and delivered to Goodrich for installation of 

the liner. The liner will be then bonded to the supporting structure. The inner diameter of 

the spool-piece as well as for the liner is 48”. 

Figure 10: Schematic of spool piece to implement HQ-liner system. 

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0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200

Frequency [Hz]

S

oun Po

wer Level [dB- ref. 10-12 

watts]

Inlet Power - Hw

Inlet Power - Liner- HQ

BPF

2 BPF

3 BPF 4 BPF

NASA/CR—2003-212097 9
 

Figure 11: Picture of aluminum supporting spool piece where liner will be mounted. 

The HQ-resonators will be mounted on the back of the liner. To allow for flexibility in 

the HQ configurations, the back plate of the liner will be a perforated plate with a high 

POA (50%) to minimize the acoustic effects, i.e. low resistance and reactance. An 

schematic of the HQ-resonator mounted on the back of the liner is shown in Figure 12. 

This figure is to scale and thus it provides a good indication of the relative size of the 

liner and HQ-waveguides. It is important to note that “relative large” size of the HQ 

devices is because of the low frequency for the 2BPF tone. In a practical implementation, 

the BPF tone of a large turbofan engine will be at higher frequency and the HQ resonator 

will be smaller (relative to the liner core depth). 

Figure 12: (a) Diagram of HQ-resonator mounted on back of liner and (b) system layout. 

The liner will be fabricated and bonded to the supporting structure. Delivery to Virginia 

Tech is expected by the end of October 2002. 

HQ-Tube

Wiremesh

Insert to 

adjust length

Liner

Plastic 

sheet

Liner back 

plate

HQ-Tube

Wiremesh

Insert to 

adjust length

Liner

Plastic 

sheet

Liner back 

plate 16”

2 Arrays of 24 

HQ-waveguides (b) (a) 

NASA/CR—2003-212097 10
2.4. Test inlet HQ-Liner-system 

The HQ-liner system designed and been built in the previous tasks will be installed and 

tested on NASA Glenn ANCF facility. Two HQ-systems will be tested corresponding to 

the optimum design for hard and soft wall conditions, respectively. The fan will be 

operated in two conditions: (a) steady state and (b) decel. In steady-state condition, the 

fan will be operated at a fixed speed in the range [1700-1900] rpm. In a decel condition, 

the fan will be set to maximum speed (~ 1900 rpm) and it will be slowly decelerated. The 

rate of deceleration will be ~3000 rpm/30 sec. 

The instrumentation to be used in these experiments is described in Table IV. It consists 

of the following systems: (a) NASA’s inlet and aft duct rotating rakes to measure modal 

amplitudes, (b) NASA’s 30-microphone inlet wall mounted array (“spool array”), (c) 

NASA’s far-field microphone array, and (d) Boeing’s 80-microphone ICD array system. 

In addition, narrow band noise spectra of selected HQ-waveguides will be recorded by 

Virginia Tech, i.e. microphones flush mounted to the tube. It is important to note that the 

ICD array technology, recently developed by Boeing to measure inlet modes, is an 

addition to the originally planned instrumentation. 

The proposed experiments are going to be performed in two phases. In the first phase 

(referred as “A”), the HQ-liner system will be implemented in the inlet of the ANCF rig. 

The rig configuration for this phase is illustrated in Figure 13 including the 

instrumentation described in Table IV. Since the spool pieces of the ANCF rig can be 

used both in the inlet and aft ducts, the HQ-liner section will be installed in the aft duct to 

perform preliminary experiments. Though not originally planned, this second 

experimental phase (referred as “B”) will be carried out if time is available in this entry. 

Table IV: Instrumentation for HQ-liner tests. 

Instrumentation Observation Responsibility 

Inlet Mic. Rake  Only for steady state condition 

 Measure Inlet Modes at BPF, 2BPF, and 

3BPF 

 Upstream direction only 

NASA Glenn 

Aft Mic. Rake  Only for steady state condition 

 Measure Aft Modes at BPF, 2BPF, and 

3BPF 

 Downstream direction only 

NASA Glenn 

Inlet Wall Mounted 

Array 

“Spool Array” 

 For steady state and decel conditions 

 Measure Inlet Modes – Tones and broadband 

 Both directions 

NASA Glenn 

Virginia Tech 

Far-Field Array  For steady state and decel conditions 

 Far-field radiation 

NASA Glenn 

Virginia Tech 

ICD Array  For steady state and decel conditions 

 Measure Inlet Modes – Tones and broadband 

 Upstream direction only 

Boeing 

NASA/CR—2003-212097 11
Figure 13: ANCF configuration for Phase “A” tests – Inlet HQ-liner configurations. 

The basic test cases to investigate are: 

a. Inlet HQ-system without liner (hard wall inlet). 

b. Inlet HQ-system with liner (soft wall inlet). 

c. Hard wall (baseline) and soft wall without the HQ-system. 

The hard wall condition will be obtained by using tape to cover the liner section. 

2.5. Data reduction and analysis: 

NASA will be responsible for acquiring the data while the post processing will rest on the 

different team members. The rotating rake data post processing will carried out by NASA 

while Virginia Tech will be responsible for the analysis of the far-field and in-duct 

arrays. Finally, Boeing will process the ICD data. Upon completion of the analysis, the 

reduced data and reports will be distributed among NASA, Goodrich, and Boeing 

personnel. 

2.6. Develop model for aft HQ-Liner-system: 

An analytical model to predict the performance of the aft HQ-Liner system applied to the 

aft duct was developed. The modeling approach was based on the same technique as used 

in the inlet duct HQ-liner system developed under a Goodrich sponsored program. Here a 

general description of the effort involved in this model development and sample results 

are presented. The complete and detailed theoretical description of the model will be 

prepared later. 

The model is based on considering the aft duct as part of an infinitely long annular duct 

with both inner and outer walls lined in a uniform flow as illustrated in Figure 14. The 

ICD

Spool with 3 circumferential arrays

of microphone - “Spool Array”

HQ-Liner Spool - “HQ-Liner Array”

Inlet Rake Hard wall Spool

Hard wall Spools

Aft Rake

ICD

Spool with 3 circumferential arrays

of microphone - “Spool Array”

HQ-Liner Spool - “HQ-Liner Array”

Inlet Rake Hard wall Spool

Hard wall Spools

Aft Rake

NASA/CR—2003-212097 12
first step on this development was to solve the eigenvalue problem at small frequency 

steps. The technique used to find the duct’s eigenproperties is by tracking the roots of the 

characteristic equations as a function of frequency starting from a hard wall condition at 

low frequency. Unlike the previous cylindrical inlet models, HQ-resonators are modeled 

in both the inner and outer surfaces of the annular duct. 

Figure 14: Annular duct with HQ-resonators mounted on both surfaces to model HQliner applied to aft duct of turbofan engines – Note liners not shown in figure. 

The aft duct model is currently been used to perform preliminary prediction of the 

performance of the HQ-liner system (same system designed for the inlet) assumed to be 

installed in the aft of the ANCF rig, i.e. hard wall for inner duct surface. Figure 15 shows 

the sound power spectrum for the hard wall (HW) and lined duct cases, i.e. no HQsystem. The results show the liner is effective at frequencies > 800 Hz. 

p p

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100 300 500 700 900 1100 1300 1500 1700 1900 2100

Frequency [Hz]

Sound Power Level [dB- ref. 10-12 watts]

Bypass Power - Liner

Bypass Power - Hw

3-BPF

BPF

2-BPF

Figure 15: Sound power level spectrum for the aft duct – Hard wall and lined outer wall. 

Inner Wall 

Outer Wall 

Flow 

NASA/CR—2003-212097 13
The sound power spectra for the hard wall and HQ-liner (again designed for the inlet) 

cases are shown in Figure 16. Comparison of the results in Figures 15 and 16 shows that 

the HQ-system is very effective at reducing the BPF tone and provide additional 

broadband attenuation at low frequencies. However, it also shows that the HQ-system is 

not effective at controlling the 2BPF tone. This last result is not unexpected since the HQ 

system was designed for the inlet. 

p p

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100 300 500 700 900 1100 1300 1500 1700 1900 2100

Frequency [Hz]

Sound Power Level [dB- ref. 10-12 watts]

Bypass Power - Liner - HQ

Bypass Power - Hw

3-BPF

BPF

2-BPF

Figure 16: Sound power level spectrum for the aft duct – Hard wall and HQ-liner system 

on outer wall. Note: HQ-liner system designed for inlet. 

2.7. Design Aft HQ-Liner-system: 

An aft HQ-liner-system will be designed for the ANCF rig configurations selected in task 

2.1. While the liner will be the same used in the inlet experiments, a new set of HQwaveguides will be designed. For this design task, fan modal amplitudes measured on the 

ANCF rig will again be required from NASA Glenn.

3. ACCOMPLISHEMENTS DURING FY02 

The key accomplishments during FY02 are: 

a) Designed a HQ-Liner system for the inlet of the ANCF rig: Using a model 

developed under a Goodrich sponsored project, an HQ-liner system was designed for 

testing on the NASA Glenn ANCF rig. A state-of-the-art linear liner used in the 

nacelles of turbofan engines was designed by Goodrich. An optimum HQ system was 

then designed by Virginia Tech for the optimum attenuation of the 2BPF tone. 

NASA/CR—2003-212097 14
b) Fabricated of HQ-liner Spool Section for ANCF rig: To implement the HQ-liner 

system, a new spool piece for the ANCF rig was designed. The liner will be bonded 

to the supporting spool piece. The spool piece was fabricated and delivered to 

Goodrich for mounting of the liner. Goodrich is now in the process of fabricating the 

liner. Virginia Tech is fabricating the HQ-resonators. The HQ-liner spool piece will 

be completed by beginning of November. 

c) Developed a model for HQ-liner system applied to the Aft duct: A model for the 

HQ-liner system applied to the aft duct section has been developed. This model will 

then be used to design an HQ-liner system for testing on the next ANCF test entry (to 

be determine). 

Though the project started on January 2003, the tasks outlined in the proposal for the first 

year has mostly been completed. The most important remaining task is to perform the 

experiments on the ANCF rig. These experiments are planned to take place during Nov.-

Dec. 2002 timeframe as originally scheduled. Thus, the program schedule is been met. 

4. REFERENCES 

1. “Fan Noise Control Using Herschel-Quincke Resonators,” R. A. Burdisso and 

W.F.Ng, NASA Glenn Research Center NRA-01-GRC-02 Aerospace Propulsion 

And Power Base Research And Technology, 1/1/02-9/30/04.

2. Smith, J. P. and Burdisso, R. A., "The Application of the Herschel-Quincke Tube 

Concept for the Reduction of Tonal and Broadband Noise From Turbofan Engines," 

VPI report VPI-ENGR.98.167, prepared for NASA under grant # NAG-1-1980 and 

proposal # 98-0448-10, 1998. 

3. R. A. Burdisso and J. P. Smith, “Control of Inlet Noise from Turbofan Engines 

Using Herschel-Quincke Waveguides,” AIAA-2000-1994, 6th AIAA/CEAS 

Aeroacoustics Conference, Maui, Hawaii, USA, 12-14 June 2000. 

4. Smith J. P. and Burdisso R. A., “Herschel-Quincke Tube Experiments on the 

Honeywell TFE731-60 Engine,” NASA 4th AST Engine/Nacelle Noise Workshop, 

Hampton, VA, November 16-18, 1999. 

5. R. Hallez and R. A. Burdisso, AIAA-2001-0816, 39th AIAA Aerospace Sciences 

Meeting & Exhibit, Reno, Nevada, USA, 8-11 January 2001. 

6. “Development of a Combined Liner Herschel-Quincke Tube System for Reduction of 

Inlet Noise from Turbofan Engines,” R. A. Burdisso, Goodrich Aerostructures 

Group, Inc. 1/1/00-12/31/02. 

NASA/CR—2003-212097 15
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NAG3–2694

22

Fan Noise Control Using Herschel-Quincke Resonators

Ricardo A. Burdisso and Wing F. Ng

Aeroacoustics; Fan noise; Noise control

Unclassified -Unlimited

Subject Categories: 07 and 71 Distribution: Nonstandard

Virginia Polytechnic Institute and State University

Vibrations and Acoustic Laboratory

Department of Mechanical Engineering

 Blacksburg, Virginia 24061

Project Manager, Andrew Provenza, Structures and Acoustics Division, NASA Glenn Research Center, organization

code 5930, 216–433–6025.

Over the last few years, the novel concept of Herschel-Quincke (HQ) waveguide resonators has been successfully applied to inlet fan

noise reduction from turbofan engines. In this project, the Vibration and Acoustics Laboratories (VAL) of Virginia Polytechnic Institute

and State University is extending this HQ-technology to the simultaneous control of radiated inlet and aft fan noise. To this end, a

series of experiments will be performed at the NASA Glenn Active Noise Control Fan (ANCF) facility, where extensive model

measurement of both the inlet and aft ducts is possible. The experiments proposed include testing of inlet and aft HQ-systems separately. Based on the results from these experiments, a test will be designed to evaluate the benefit of the simultaneous implementation

of inlet and aft HQ-systems. For the above experiments the HQ-systems will be integrated with state-of-the-art acoustic liners which

will provide a realistic evaluation of the potential of the HQ-technology in "production" turbofan engines. Goodrich Aerospace,

Aerostructures Group (Rohr), through both financial and hardware contributions is supporting this program. The financial support is for

the development of an analytical model to predict the noise reduction performance of the aft HQ-system, the design of experiments,

and data analysis. Goodrich is also providing the liners to be used in the ANCF experiments. This report describes the work performed

for the first year effort corresponding to the period from January through September 2002 of FY02. For the sake of brevity, the most

important results and accomplishments are described here. A full detailed report including predicted and experimentally measured

results will be prepared upon completion of the first set of experiments during November through December 2002.