8/12/2019 Penn State Leverton 1 CD 2013
1/93
Penn State August 2013Leverton Associates International
August 2008
Dr John W LevertonLeverton Associates
International
August 2013
8/12/2019 Penn State Leverton 1 CD 2013
2/93
8/12/2019 Penn State Leverton 1 CD 2013
3/93
Penn State August 2013Leverton Associates International
SOUND MEASUREMENTS
METRICS FOR MEASUREMENTAND ANALYSIS OF AIRCRAFT
NOISE
8/12/2019 Penn State Leverton 1 CD 2013
4/93
Penn State August 2013Leverton Associates International
HearingResponse
8/12/2019 Penn State Leverton 1 CD 2013
5/93
Penn State August 2013Leverton Associates International
LoudnessPhons
8/12/2019 Penn State Leverton 1 CD 2013
6/93
Penn State August 2013Leverton Associates International
Equal Loudness Curves ISO 226
8/12/2019 Penn State Leverton 1 CD 2013
7/93Penn State August 2013Leverton Associates International
Relationship between loudness in Sonesand loudness level in Phons.
LOUDNESS
8/12/2019 Penn State Leverton 1 CD 2013
8/93Penn State August 2013Leverton Associates International
NOISINESSUnit of NOYS used as basisfor EPNdB
8/12/2019 Penn State Leverton 1 CD 2013
9/93Penn State August 2013Leverton Associates International
WEIGHTING CURVES
8/12/2019 Penn State Leverton 1 CD 2013
10/93Penn State August 2013Leverton Associates International
WEIGHTINGCURVES
8/12/2019 Penn State Leverton 1 CD 2013
11/93Penn State August 2013Leverton Associates International
SOUND PRESURE LEVEL (SPL)FREQUENCY & PERIOD
SPL ( Sound Pr essure Level ) = 10 log P 2 = 20 log PPref 2 P ref
8/12/2019 Penn State Leverton 1 CD 2013
12/93Penn State August 2013Leverton Associates International
sPL = 10 log (P 2/P ref 2) Sound I ntensi ty or Energy
= 10 log (P/P ref )2
= 20 log (P/P ref )
If Two Equal Sources . Sources SPL = 10 log (P/P ref )2 + 10 log (P/P ref )2
= + 3 dB
If Pressure Doubled
SPL = 20 log (2 x P/P ref )
= + 6 dB
SOUND PRESSURE LEVEL (SPL)
8/12/2019 Penn State Leverton 1 CD 2013
13/93Penn State August 2013Leverton Associates International
Summation ofTwo Sources
8/12/2019 Penn State Leverton 1 CD 2013
14/93Penn State August 2013Leverton Associates International
Noise Reduction with Distance
6 dB per
doubling orhalving ofdistance
SPL = 20 log (d/d ref)
Doubling of Distance = + 6 dB
8/12/2019 Penn State Leverton 1 CD 2013
15/93Penn State August 2013Leverton Associates International
Wavelengths
Wavelengths in Air undernormal conditions
8/12/2019 Penn State Leverton 1 CD 2013
16/93Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
17/93Penn State August 2013Leverton Associates International
L A MAXL A
Sound Exposure Level - SEL (L AE )
Often r eferenced:
Single Event Level
Sound Event Level
.... there is also a Single Event Noise Exposure Limit (SENEL) used in California State .
8/12/2019 Penn State Leverton 1 CD 2013
18/93Penn State August 2013Leverton Associates International
L A MAXL A
Sound Exposure Level - SEL (L AE )
8/12/2019 Penn State Leverton 1 CD 2013
19/93Penn State August 2013Leverton Associates International
Sound Exposure Level - SEL (L AE )
8/12/2019 Penn State Leverton 1 CD 2013
20/93Penn State August 2013Leverton Associates International
1/3 Octave Bands / Octave Bands
8/12/2019 Penn State Leverton 1 CD 2013
21/93Penn State August 2013Leverton Associates International
PNdB ~PNL
See Handout forNoise Certification
PNL/EPNdBCalculation
Noise
CertificationEPNdB
8/12/2019 Penn State Leverton 1 CD 2013
22/93Penn State August 2013Leverton Associates International
EPNdBdB(A)max/dBA M
SEL/L AE
Max Level
10dB
10dB
Measured Noise Levels
8/12/2019 Penn State Leverton 1 CD 2013
23/93
Penn State August 2013Leverton Associates International
Community Noise Levels
Rotorcraft Flyover
8/12/2019 Penn State Leverton 1 CD 2013
24/93
Penn State August 2013Leverton Associates International
Ground Reflection of Sound
8/12/2019 Penn State Leverton 1 CD 2013
25/93
Penn State August 2013Leverton Associates International
Sound Reflection due to Wind
8/12/2019 Penn State Leverton 1 CD 2013
26/93
Penn State August 2013Leverton Associates International
Sound Reflection due to Temperature
8/12/2019 Penn State Leverton 1 CD 2013
27/93
Penn State August 2013Leverton Associates International
TypicalNoise / Sound Levels
8/12/2019 Penn State Leverton 1 CD 2013
28/93
Penn State August 2013Leverton Associates International
TypicalNoise / Sound
Levels
8/12/2019 Penn State Leverton 1 CD 2013
29/93
Penn State August 2013Leverton Associates International
Flyover Noise / Typical Ambient Noise
8/12/2019 Penn State Leverton 1 CD 2013
30/93
Penn State August 2013Leverton Associates International
Amplitude vs. Time and Frequency
8/12/2019 Penn State Leverton 1 CD 2013
31/93
Penn State August 2013Leverton Associates International
VARIATION OF NOISEWITH
TEMPERATUREAND
RELATIVE HUMIDITY
8/12/2019 Penn State Leverton 1 CD 2013
32/93
Penn State August 2013Leverton Associates International
Variation of 1/3 Octave Spectrum with Distance
8/12/2019 Penn State Leverton 1 CD 2013
33/93
Penn State August 2013Leverton Associates International
Variation of 1/3 Octave Spectrum with Distance
8/12/2019 Penn State Leverton 1 CD 2013
34/93
Penn State August 2013Leverton Associates International
ACOUSTIC CHARACTERISTICS
OF ROTORCRAFT
8/12/2019 Penn State Leverton 1 CD 2013
35/93
Penn State August 2013Leverton Associates International
dB
8/12/2019 Penn State Leverton 1 CD 2013
36/93
Penn State August 2013Leverton Associates International
Helicopter Noise Sources
Approach
BVI/Blade Slap
can be higherand dominate
8/12/2019 Penn State Leverton 1 CD 2013
37/93
Penn State August 2013Leverton Associates International
Flyover
+
Takeoff
Helicopter Noise Sources
8/12/2019 Penn State Leverton 1 CD 2013
38/93
Penn State August 2013Leverton Associates International
Helicopter Noise Sources
Flyover BVI/Blade Slap* not indicate
BVI/Blade Slap = Main Rotor/Main Rotor Tip Vortex Interaction
8/12/2019 Penn State Leverton 1 CD 2013
39/93
Penn State August 2013Leverton Associates International
MAIN ROTOR TIP VORTEX TRAJECTORIESDURING HOVER AND FORWARD FLIGHT - LYNX
8/12/2019 Penn State Leverton 1 CD 2013
40/93
Penn State August 2013Leverton Associates International
Narrowband, Frequency or Spectrum Analysis
8/12/2019 Penn State Leverton 1 CD 2013
41/93
Penn State August 2013Leverton Associates International
Narrowband,Frequency
or SpectrumAnalysis
8/12/2019 Penn State Leverton 1 CD 2013
42/93
Penn State August 2013Leverton Associates International
Narrowband,
Frequencyor SpectrumAnalysis
BVI/Blade Slap
8/12/2019 Penn State Leverton 1 CD 2013
43/93
Penn State August 2013Leverton Associates International
Pressure TimeHistory
BVI/Blade Slap
8/12/2019 Penn State Leverton 1 CD 2013
44/93
Penn State August 2013Leverton Associates International
Hovering Wessex Impact of Wind
8/12/2019 Penn State Leverton 1 CD 2013
45/93
Penn State August 2013Leverton Associates International
Time History BVI/Blade Slap
8/12/2019 Penn State Leverton 1 CD 2013
46/93
Penn State August 2013Leverton Associates International
Flyover Time History
8/12/2019 Penn State Leverton 1 CD 2013
47/93
Penn State August 2013Leverton Associates International
Generalized dB(A) Flyover Time History
8/12/2019 Penn State Leverton 1 CD 2013
48/93
Penn State August 2013Leverton Associates International
Helicopter with no HSI, no BVI, no TRIand low Tail Rotor (TR) Noise
HSI High Speed Impulsive Noise / Thickness Noise
Generalized dB(A) Flyover Time History
8/12/2019 Penn State Leverton 1 CD 2013
49/93
Penn State August 2013Leverton Associates International
Helicopter with High Levels of HSI, BVI,Tail Rotor (TR) and/or TRI Noise
TRI or Tail Rotor (TR) Noise
Helicopter with no HSI, no BVI, no TRIand low Tail Rotor (TR) Noise
HSI High Speed Impulsive Noise / Thickness NoiseBVI Blade Vortex Interaction (Blade Slap)
TRI - Tail Rotor (Main Rotor Wake) Interaction
Flyover Noise
8/12/2019 Penn State Leverton 1 CD 2013
50/93
Penn State August 2013Leverton Associates International
Helicopter with High Levels of HSI, BVI,Tail Rotor (TR) and/or TRI Noise
TRI or Tail Rotor (TR) Noise
Helicopter with no HSI, no BVI, no TRI
and low Tail Rotor (TR) Noise
Flyover Noise High HSI/Thickness Noise or BVI/Blade Slap
8/12/2019 Penn State Leverton 1 CD 2013
51/93
Penn State August 2013Leverton Associates International
Helicopter with High Levels of HSI, BVI,Tail Rotor (TR) and/or TRI Noise
TRI or Tail Rotor (TR) Noise
Helicopter with no HSI, no BVI, no TRIand low Tail Rotor (TR) Noise
Flyover Noise High Tail Rotor Noise
8/12/2019 Penn State Leverton 1 CD 2013
52/93
Penn State August 2013Leverton Associates International
Helicopter with High Levels of HSI, BVI,Tail Rotor (TR) and/or TRI Noise
TRI or Tail Rotor (TR) Noise
Helicopter with no HSI, no BVI, no TRIand low Tail Rotor (TR) Noise
Flyover Noise Public Acceptance
8/12/2019 Penn State Leverton 1 CD 2013
53/93
Penn State August 2013Leverton Associates International
ROTOR NOISE GENERATION
8/12/2019 Penn State Leverton 1 CD 2013
54/93
Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
55/93
Penn State August 2013Leverton Associates International
ROTATIONAL NOISE
8/12/2019 Penn State Leverton 1 CD 2013
56/93
Penn State August 2013Leverton Associates International
FUNDAMENTAL (1st Harmonic)
8/12/2019 Penn State Leverton 1 CD 2013
57/93
Penn State August 2013Leverton Associates International
Rotational NoiseHarmonic Level (SPL)
vs. Thrust
* 160 RPM - 461 ft/sec 205 RPM - 593 ft/sec
230 RPM 670 ft/sec
260 RPM 758 ft/sec
T 2 = (Thrust) 2
T 2 = (Thrust) 2
T 0 = Independent of Thrust
160 RPM461 ft/sec
260 RPM758 ft/sec
FUNDAMENTAL (1st Harmonic)
5th Harmonic
10th Harmonic
20th Harmonic
30th Harmonic
2 BLADED S-55 ROTOR
Rotational Noise
8/12/2019 Penn State Leverton 1 CD 2013
58/93
Penn State August 2013Leverton Associates InternationalBlade Tip Mach Number
Rotational NoiseHarmonic Level (SPL) vs. Rotor Tip Speed
8/12/2019 Penn State Leverton 1 CD 2013
59/93
Penn State August 2013Leverton Associates International
Rotational NoiseHarmonic Level (SPL) vs. Rotor
Tip Speed
o 0 lbs
700 lbs
+ 1850 lbs
x 3050 lbs
2 BLADED S-55 ROTOR
V12
V6
758
0 lbs
3050 lbs
8/12/2019 Penn State Leverton 1 CD 2013
60/93
Penn State August 2013Leverton Associates International
Main Rotor Rotational Noise Harmonic ;Fall- off
8/12/2019 Penn State Leverton 1 CD 2013
61/93
Penn State August 2013Leverton Associates International
Rotational Noise
Directivity
8/12/2019 Penn State Leverton 1 CD 2013
62/93
Penn State August 2013Leverton Associates International
LOW FREQUENCYBROADBAND NOISE
8/12/2019 Penn State Leverton 1 CD 2013
63/93
Penn State August 2013Leverton Associates International
Broadband Noise Spectra
8/12/2019 Penn State Leverton 1 CD 2013
64/93
Penn State August 2013Leverton Associates International
Low Frequency Broadband Noise Analysis Model
8/12/2019 Penn State Leverton 1 CD 2013
65/93
Penn State August 2013Leverton Associates International
Low Frequency
Broadband Noise
Flat SPL vs. Thrust
8/12/2019 Penn State Leverton 1 CD 2013
66/93
Penn State August 2013Leverton Associates International
Low FrequencyBroadband Noise
Flat SPL vs. Tip Speed
8/12/2019 Penn State Leverton 1 CD 2013
67/93
Penn State August 2013Leverton Associates International
Low FrequencyBroadband Noise
and
Total (Overall)
Rotor NoiseNoise Directivi ty
2 Bladed (S55) Rotor250 ft radius
8/12/2019 Penn State Leverton 1 CD 2013
68/93
Penn State August 2013Leverton Associates International
ROTOR ACOUSTICSTHEORETICAL ASPECTS
Acoustics Theory
8/12/2019 Penn State Leverton 1 CD 2013
69/93
Penn State August 2013Leverton Associates International
Lighthill (1952)
redefined by Ffowcs-Williams and Hawkings (1969)
Acoustics Theory
Acoustics Theory
8/12/2019 Penn State Leverton 1 CD 2013
70/93
Penn State August 2013Leverton Associates International
Lighthill (1952)
redefined by Ffowcs-Williams and Hawkings (1969)
Acoustics Theory
Aerodynamic Sound = Monopole + Dipole + Quadrupole Sources
Monopole blade volume or thickness noise
Dipole blade ( fluctuating ) force or lift noise
Quadrupole - high speed effect s: transonic compressibility
flow, shock and viscous flow
Acoustics Theory
8/12/2019 Penn State Leverton 1 CD 2013
71/93
Penn State August 2013Leverton Associates International
Lighthill (1952)
redefined by Ffowcs-Williams and Hawkings (1969)
Acoustics Theory
Dipole Source
where: r = distance from observer to sourceco = speed of sound
Fi = fluctuating force(t-r/c o) = retarded time
Acoustics Theory
8/12/2019 Penn State Leverton 1 CD 2013
72/93
Penn State August 2013Leverton Associates International
Lighthill (1952)
redefined by Ffowcs-Williams and Hawkings (1969)
Acoustics Theory
Dipole Source far field
where: Ls = loading per unit spanxn = coordinate normal to the span.
8/12/2019 Penn State Leverton 1 CD 2013
73/93
Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
74/93
Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
75/93
8/12/2019 Penn State Leverton 1 CD 2013
76/93
Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
77/93
Penn State August 2013Leverton Associates International
BladeLoading
Blade Loading
8/12/2019 Penn State Leverton 1 CD 2013
78/93
Penn State August 2013Leverton Associates International
R i l N i P di i
8/12/2019 Penn State Leverton 1 CD 2013
79/93
Penn State August 2013Leverton Associates International
Rotational Noise Prediction
8/12/2019 Penn State Leverton 1 CD 2013
80/93
Penn State August 2013Leverton Associates International
BladeLoading(Force)
NoisePredictions
8/12/2019 Penn State Leverton 1 CD 2013
81/93
Penn State August 2013Leverton Associates International
Directivity Moving Dipole
Rotor Wake Calculation
8/12/2019 Penn State Leverton 1 CD 2013
82/93
Penn State August 2013Leverton Associates International
Rotor Wake Calculation
8/12/2019 Penn State Leverton 1 CD 2013
83/93
Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
84/93
Penn State August 2013Leverton Associates International
MAIN ROTOR TIP VORTEX TRAJECTORIESDURING HOVER AND FORWARD FLIGHT - LYNX
8/12/2019 Penn State Leverton 1 CD 2013
85/93
Penn State August 2013Leverton Associates International
Wake Modeling
Fluctuating Load and Acoustic Pressure Calculations
8/12/2019 Penn State Leverton 1 CD 2013
86/93
Penn State August 2013Leverton Associates International
Fluctuating Load and Acoustic Pressure Calculations
[Westland H elicopters Ltd]
BVI/Blade Slap Calculations
8/12/2019 Penn State Leverton 1 CD 2013
87/93
Penn State August 2013Leverton Associates International
Peak Pressure Directivity6 descent/ 70 knots
Forward Speedvs.
Descent Angle
Thickness Noise
8/12/2019 Penn State Leverton 1 CD 2013
88/93
Penn State August 2013Leverton Associates International
Thickness Noise
Thickness Noise
8/12/2019 Penn State Leverton 1 CD 2013
89/93
Penn State August 2013Leverton Associates International
8/12/2019 Penn State Leverton 1 CD 2013
90/93
Penn State August 2013Leverton Associates International
Thickness Noise
Prediction
8/12/2019 Penn State Leverton 1 CD 2013
91/93
Penn State August 2013Leverton Associates International
ThicknessNoise
Predictions
HSI/Thickness Noise - Directivity
8/12/2019 Penn State Leverton 1 CD 2013
92/93
Penn State August 2013Leverton Associates International
S / c ess o se ect v ty
Peak Acoustic Pressure
143 knot level flight
0
10
20
30
40
50
60
70
80
90
100
centreline
Vertical Directivity
P di ti A
8/12/2019 Penn State Leverton 1 CD 2013
93/93
Prediction Accuracy