AD-R154 063 OPERATIONAL NOISE DATA FOR THE LACV-38 AIR CUSHION 1/1VEHICLE(U) CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY)CHAMPRIGN IL P SCHOMER MAR 85 CERL-TR-N-85/84

UNCLASSIFIED IRO-R4105 F/G 28/1 NL

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US Army Corpsof Engineers TECHNICAL REPORT N-85/04Construction Engineering March 1985

*AD-A 154 063

| .7,

OPERATIONAL NOISE DATA FOR THE LACV-30

AIR CUSHION VEHICLE

byPaul D. Schomer

Operational data for the LACV-30 air cushiont

vehicle were gathered and developed into soundexposure level vs. distance curves. These data areavailable for the Army Environmental HygieneAgency (AEHA) to use in developing noise zonemaps for LACV-30 operations in support of theArmy Installation Compatible Use Program (ICUZ).ICUZ defines land uses compatible with variousnoise levels and establishes a policy for achieving suchUses.

Although the Army classifies the LACV-30 as anamphibious vehicle, an examination of its noise

- : ) characteristics and operations showed it most closely*resembles a helicopter. Thus the methodology for

gathering rotary wing aircraft data was used. Measure-g..J ments of LACV-30's passby runs over water at- various distances and speeds were similar in concept

LA_ to flyover and flyby measurements for helicopters,and the land maneuver measurements correspondedmost nearly to a helicopter's hover measurements. MAY2 2 S85

B :.Approved for public release: distribution unlimited.

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The contents of this report are not to be used for advertising, publication, orpromotional purposes. Citation of trade names does not constitute anofficial indorsement or approval of the use of such commercial products.The findings of this report are not to be construed as an official Departmentof the Army position, unless so designated by other authorized documents.

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OPERATIONAL NOISE DATA FOR THE LACV-30 FINAL

AIR CUSHION VEHICLE _ _-__ _

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P. Schomer iAO-A4 105 .

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I. KEY WORDS (Continue on reverse elde if necessmy and Identify by block number)

1ACV-30 air cushion vehicle

air cushion vehicleSound cxposure levelnoise(sound)

!1L ABSTRACT (Ctm anrvese eftb N teeee amd Identify by block nmthbef)

Operational data tor the LACV-30 air cushion vehicle were gathered and developed .into sound exposure level vs. distance curves. These data are available for the Army En-vironmental Hygiene Agency (AEHA) to use in developing noise zone maps for LACV-30operations in support of the Army Installation Compatible Use Program (ICUZ). ICUZdefines land use compatible with various noise levels and establishes a policy for achievingsuch uses.

Although the Army classifies the LACV-30 as an amphibious vehicle, an examination --. > L

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4. BLOCK 20 (Continued)

* -,of its noise characteristics and operations showed it most closely resembles a helicopter.Thus the methodology for gathering rotary wing aircraft data was used. Measurements of

* LACV-30's passby runs over water at various distances and speeds were similar in conceptto tlyover and flyby measurements for helicopters, and the land maneuver measurements ~corresponded most nearly to a helicopter's hover measurements. u/

-zl.

FOREWORD

This study was conducted for Fort Belvoir, VA. Research and Development Center(STRB-E-4;RD), under IAO-A4105, dated January )984.

The work was performed by the Environmencttal Division (EN) of the U.S. ArmyConstruction Engineering Research ULaboratory (USA-Cf, RL). Dr. R. K. Jain is Chief of'

* LJSA-CERL-EN.

COL Paul J. Theuer is Commander and Director of USA-CERL, and Dr. L. R. Shafferis Technical Director.

3,

CONTENTS

pap.

DD FORM 1473 2FOR EWORD 3LIST OF TABLES AND FIGURES 5

1 INTRODUCTION............................................ 7Background

Mod of TEU echniolog Transfer

2 TES OPERTIONSAND DATA COLLECTION METHODS .............. 7

DATA REDUCTION AND RESULTS ............................... 8

PassbyData

4NOISE SOURCES AND POTENTIAL NOISE MITIGATION METHODS ...... 16

5 CONCLUSION............................................. 19

APPEN DIX: SEL vs. Distance Tables for Microphones 1, 2, and3 Averaged Over Various Typos of Operations 20

DISTRIBUTION

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TABLES

Number Page

I Overwater Passby Operations 11

2 Overland Maneuvers 13

3 LACV-30 Operational Noise Level vs. Distance Data 19 IAl Key to Appendix Tables 20

A2 SEL vs. Distance Averaged Over 1/4 nrni at Cruise Speed,Jan 5,6, Traveling East and West 20

A3 SEL vs. Distance Averaged Over 1/2 nmi at Cruise Speed,Jan 5, 6, Traveling East and West 20

A4 SEL vs. Distance Averaged Over 1/8 nmi at Cruise Speed,Jan 5, 6, Traveling East and West 20 1%

AS SEL vs. Distance, Set 1, Averaged Over 1/4 nmi at Cruise Speed,Jan 5, 6, Traveling East and West 21

A6 SEL vs. Distance, Set 2, Averaged Over 1/4 nmi at Cruise Speed,Jan 6, Traveling East and West 21

A7 SEL vs. Distance, Set 1, at Cruise Speed, for All Distances,Jan 5, Traveling East and West 21

A8 SEL vs. Distance, Set 2, at Cruise Speed, for All Distances,Jan 6, Traveling East and West 21

A9 SEL vs. Distance, Cruise Speed, Traveling East, for All Distances,Jan 5, 6 22

A1O SEL vs. Distance, Cruise Speed, Traveling West, for All Distances,Jan 5, 6 22 I.

Al I SEL vs. Distance, Cruise Speed, Jan 5, 6, Traveling East and West,for All Distances 22

A l 2 SEL vs. Distance for 1/8 and 1/4 nmi at Cruise Speed,Traveling East and West, Jan 5,6 22

A1 3 SEL vs. Distance, Set 1, 1/4 nmi at High Speed, Traveling Eastand West, Jan 5 23

A14 SEL vs. Distance, Set 2, 1/4 nmi at High Speed, Traveling Eastand West, Jan 6 23

AI5 SEL vs. Distance, Over 1/4 nmi at High Speed, Traveling East and West,Jan 5, 6 23

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Tables (Cont'd)

Number Page

A b SEL vs. Distance, Set 1, 1/4 nmi at Below Hump Speed, TravelingEast and West, Jan 5 23 -.

A17 SEL vs. Distance, Set 2, 1/4 nmi at Below Hump Speed, TravelingEast and West, Jan 6 24

Al 8 SEL vs. Distance, 1/4 nmi at Below Hump Speed, Traveling Eastand West, Jan 5,6 24

FIGURES

Number Page

I General site layout for LACV-30 noise measurements. 9

2 Passby paths and microphone locations. 10

3 Test site layout for land maneuver measurements of the LACV-30. 12

4 Land maneuver patterns for the LACV-30. 13

5 Measurement equipment at a site. 14

6 SEL vs. distance for cruise speed. 15

7 SEL vs. distance, for cruise, high, and below hump speeds. 17

8 The l/3-octave spectra of a maneuvering craft at a distance of 275 m. 18

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OPERATIONAL NOISE DATA Previous USA-CERL research has addressed, toFOR THE LACV-30 some degree, these sets of data for rotary-wing aircraftAIR CUSHION VEHICLE and for blast noise prediction, but no previous work

addressed the noise emissions of the LACV-30 aircushion vehicle, a significant source of noise at some

installations.4 (USA-CERL was asked by Fort Belvoir,INTRODUCTION VA, Research and Development Center to measure the

noise emissions of the LACV-30 in accordance with

Background AR 200-1.)

In recent years, residential development has occurred Objectivenear military installations areas subject to high noise The objective of this study was to develop soundlevels. To ensure that this development does not affect exposure level (SEL) vs. distance curves for the LACV-the operating capabilities of those installations, the 30 for use in developing noise zone maps. As a side jU.S. Army has instituted the Installation Compatible benefit to this study, some potential reasons for the

Use Zone Program (ICUZ).' Like the Departmrent of vehicle's high noise emissions were also determined,Defcnse's (DOD) Constnction Criteria Manual and Air and they are presented with suggestions for mitigation.Installation Compatible Use Zone program (AICUZ), .

the IC('Z program defines land uses compatible with Approachvarious noise levels attd establishes a policy for achieving Since the LACV-30 is a unique vehicle in the Army,such uses.) The ICUZ program stresses Army-unique the first step was to determine what methodology tonoise sources such as blasts (e.g., from artillery, use. The Army has chosen to classify the LACV-30 as aarmor, demolition) and rotary-wing aircraft. marine vehicle because its use is the amphibious off-

loading of materials from ship to shore. However, itsNoite zo,,e maps for the ICUZ program are devel- operation, construction, and noise source character-

oped by the Army Environmental Hygiene Agency istics most closely resemble those of a helicopter or(ALIlA) using the U.S. Army Construction Engineer- fixc. wing aircraft; thus the basic methodology used totog Research Laboratory's (USA-CERL) Integrated characterize rotary wing aircraft noise was chosen. TheNoise Contour System (INCS). This system can pro- passby noise emission measurements were made likeduce Joi lt noise /one maps for blast noise and fixed- the flyby measurements of a helicopter. Overlandand rotary-wing aircraft operations. Blast noise zone maneuvering noise emissions were characterized like anaps are produced using the USA-CERL-developed helicopter's hover operation.BNOISE-3.2 computerized prediction procedure, heli- ,'.copter noise zone tnaps are developed using a USA- Mode of Technology Transfer

CLRL-tnodified Air Force NOISE MAP Computer Data developed for LACV-30 SEL vs. distance or

Pr2diction Program.' Each of these computerized speed will be entered in the INCS input data base andprediction methods relies on three separate data sets: will be immediately available for use by AEHA and

I ) source emissions data, (2) data detailing sound other DOD installations.propagation from source to receiver, and (3) datadefining the human and community response to the ,."

received noise. 1 TEST OPERATIONS AND_DATA COLLECTION METHODS

'Installatim Comtpatible Avoise use Zones (Department of'the Arm. Office ,of the Adjutant General, 20 May 1981). LACV-30 Operations

'Cmstrtuion Criteria Manual. DOD 4270.1-M (Depart- The LACV-30 hovers and flies through the air a fewment oft De .nse. 1972): Air Installations Compatible Use " "s

lones. DOD Instruction 4165-57 (Department of Defense, centimeters off the surface of water or land. Two types

1973)

Lino,ln L. Little, Violetta I. Pawlowska, and David L. *B. Homans, L. Little, and P. Schomer, Rotar. Wing Air-

I flind, Blast Aoise Prediction Volume If: BNOISE 3.2 Com- craft Operational Noise Data. Technical Report N-38/ADApurer Program Description and Program Listing, Technical 051999 (USA-CERL, 1978); P. D. Schomer, Aaron Averbuch,Report ,-98 AtA099335 (.S. Army ('onstruction Engin- and Richard Raspet. Operational Noise Data for UH-60A and

eering Research Laboratory I USA-CERL 1, 1981); R. D. Horon- CH-47C Army Helicopters. Technical Report N-131/AlI87%

Jeff, R. R. Kandukuri, and N. H. Reddingius, Community (USA-CERL, 1982).,Vois,' k Sposuro" Resulting From Aircraft Operation. Computer 'AR 200-1, Environmental Protection and EnhancementProgram Description. Air Iorce Report AMRL TR-73-109/ (Hleadquarters, Department of the Army IHQDAI, 15 JuneADAt04821 (1974). 1982), p 7-5.

7

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of opelattons were pertoiuted fr this study: overwater equivalent level (LEQ) at a known distance was devel-passbys and overland maneuvering. The overwater pass- oped from the maneuvering craft, and because of thebys consisted mainly of straight line operation 1/4 measurement procedures, the equivalent spectrum wasnautical mile (nmi)* from shore at various speeds. available from the tape recordings. Table 2 lists theSeveral measturements were also taken at 1/8 and 1/2 overland maneuvers.

Measurement InstrumentationFigures 1 and 2 illustrate the microphone setup for The same measurement instrumentation was used at

the overwater passbys. Tile measurements were per- all locations (positions I through 5 at tile overwaterformed during early January 1984 at Fort Story, VA. site and positions 1 through 5 at the overland maneu-Three primary microphones were located on a rocky vering site). Each station consisted of a B&K 4921bluff about 3 in above the sea level, and about 30 in 1/2-inch quartz coated outdoor microphone system. ,.from one another. Tile LACV-30 followed one of the The microphone signal went to the USA-CERL-three paths illustrated in Figures I and 2. These paths developed true-integrating environmental noisewere respectively 1/8, 1/4, or 1/2 nmi from the monitor and sound exposure level meter and to apriuary measurement location and were otherwise Nagra DJ tape recorder.parallel to a line tangent to the shoreline at the primarymeasurement location. Secondary measurements were Figure 5 illustrates the typical station setup. Themade inland at locations 4 and 5 in Figure 2. only difference between sites was that the overwater

passby remote sites (stations 4 and 5) used 12-V

The overwater test consisted primarily of a set of storage batteries for power while all the other stationspasshys at tile 1/4-nmi distance, with supplemental were powered from the mobile acoustics van, con-

data at 1/8 and 1/2 nmi. In all passbys, the craft fol- nected to a 110-V generator or 110-V commerciallowed tile paths indicated in Figure I, making turns power.

within 1/2 rnii of the edge of the training area. Thecraft was heavily loaded with a 16-ton container during Meteorological data were gathered using the USA-

the test. Operating speeds at 1/4 nmi included typical CERL tethered helium balloon system, a commerciallycruise speed (roughly 40 lb torque), maximum speed made meteorological sensor which measures wind(roughly 48 to 50 lb torque), and low, or just below speed, wind direction, temperature, and humidity at"hump" speed (roughly 33 to 36 lb torque). Below various altitudes. The altitudes for this set of measure-hump is when the craft is plowing through rather than mnents ranged from about 3 to 45 m above the ground.

"flying" over the water.

During the passby tests only one craft was opera-tional, so the same craft was used on two consecutive DATA REDUCTION AND RESULTSdays with two different crews. On the first day, theI/4-nui measurements were augmented with one setof typical cruise speed measurements at 1/2 nmi. On The acoustical data were reduced similar to the waytile second day. the l/4-nni measurements were SEL vs. distance curves are calculated for flybys ofaugmented by typical cruise speed measurements at rotary-wing aircraft and similar to how the LEQ vs.1,!8 nrni. Table I lists the overwater passby operations distance is calculated for a hovering rotary-wingperforined. aircraft.

Maneuvering measurements were taken as the Passby Dataopecrator steered the craft through some fairly tight Tile passby data were reduced by microphoneturns in circles and figure eights in sand dines. Figure location and operation to standard day (I 5oC and 70173 illustrates the overland measurement setup and the relative humidity) SEL vs. distance curves. The basic

locations of the five microphones. The craft executed data consisted of the field measured A-weighted SELthe two maneuvers illustrated in Figure 4, around the at a site for a passby. and the tape-recorded data. Thetwo duties shown in Figure 3. In essence. A-weighted tape-recorded data were used to develop the time at

which the 32-second true Root-Mean-Square (RMS)maximum A-weighted value occurred and from this ,.

to determine the 1/3-octave spectrum during that*Onc nauticalm ilc 1828 in. 32-second period. The 32-second time period (in

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Table A 17 Table A 18

SEL vs. D~istance, Set 2. 1/4 ilmi at Below Hump SEL vs. Distance, 1/4 nmi at Below Hump Speed,Speed, Traveling East and West, Jan 6 Traveling East and West, Jan 5, 6

lor)Al 11iuiibl :iveragcdl 1) Total number averaged: 21A~erijgc ilistinci' 457-10 in Average distance: 457.20 in

\vl ccItuive humidity: 74.60 percent Average relative humnidity: 85.06 percent\icinlpeiatLIIe: 14.50 Ci Average temperature: 13.19 0C

AVCrA w [11,iv. SOund level: 90.40 dB Average max. sound level: 93.68 dB,\%eiige ASI- L: I 1 .39 dIB Average ASEL: 114.07 dB

Distance Average ASEL Distance Average ASEL%(Mn) (d B) (in) (dB).

Mi122.0 50 124.8IO)118.9 100 121.6

NO( 115.6 200 118.311 f0.9 500 113.5

'Io 10)I6.7 1000 109.2Iul 10.5 2000 103.9

01191.9 5000 94.282.3 10000 84.9

24

Table A 13 Table A 15

SEL vs. Distance, Set 1, 1/4 nmi at High Speed, SEL vs. Distance, Over 1/4 nmi at High Speed,

Traveling East and West, Jan 5 Traveling East and West, Jan 5, 6

Total number averaged: 12 Total number averaged: 24Aveiage distance: 45 7.10111 Average distance: 457.20 mAverage relative humidity: 93.70 percent Average relative humidity: 85.50 percentAveiage temperature: 11.,60 0C Average temperature: I 2.700CAverage mnax. sound level: 94.40 dB Average max. sound level: 90.95 dBA~c~a~ve ASEL: 1 11.23 dB Average ASEL. ,07.55 dB

Distance Average ASEL Distance Average ASEL(in) (d8) (in) (dB)

5o 122.1 s0 118.31(10 118.9 100 115.12Loo 115 5 200 111.8

M'110.6 500 107.01 (10( 106.1 1000 102.72000 100.8 2000 97.5

oo92.1 5000 89.0100 00 85.4 10000 82.0

Table A 14 Table A 16

SEL vs. Distance, Set 2, 1/4 nmi at High Speed, SEL vs. Distance, Set 1, 1/4 nmi at Below HumpTraveling East and West, Jan 6 Speed, Traveling East and West, Jan 5

[otal number averaged: 12 Total number averaged: 12Average distance: 457.20 rn Average distance: 457.20 mnAverage relative humidity: 77.30 percent Average relative humidity: 92.90 percent..\erage temperature: 13.80 0C Average temperature: I 2.20 0CAvera~re max. sound level: 87.51 dB Average max. sound level: 96.14 dBAverage ASEL: 103.88 dB Average ASEL: 116.08 dB

Distance Average ASEL Distance Average ASEL(ml) (dB) (in) (dB)

5(1 114.5 50 126.8111(1 111.4 100 123.6200 108. 200 120.35001 103.3 500 115.5

1 000) 99.2 1000 111.120100 94.2 2000 105.750001 85.8 5000 96.0

10000 78.5 10000 86.7

23

%

Table A9 Table AI l

SEL vs. Distance, Cruise Speed, Traveling East, for All SEL vs. Distance, Cruise Speed, Jan 5, 6, TravelingDistances, Jan 5, 6 East and West, for All Distances

Total number averaged: 21 Total number averaged: 45Average distance: 556.47 in Average distance: 535.22Average relative humidity: 85.66 percent Average relative humidity: 85.10 percentAverage temperature: 12.95 0 C Average temperature: 13.01 0CAverage inax. sound level: 93.61 dB Average max. sound level: 92.47 dBAverage ASEL: 109.88 dB Average ASEL: 110.13 dB

Distance Average ASEL Distance Average ASEL(M) (dB) (M) (dB)

50 122.7 50 122.9100 118.7 100 118.8200 115.0 200 114.9500 110.0 500 110.01000 105.6 1000 105.72000 100.1 2000 100.45000 90.6 5000 91.410000 82.0 10000 83.5

Table AlO Table A12

SEL vs. Dista-ce, Cruise Speed, Traveling West, for All SEL vs. Distance for 1/8 and 1/4 nmi at Cruise Speed,Distances, Jan 5, 6 Traveling East and West, Jan 5, 6

Total number averaged: 24 Total number averaged: 33Average distance: 516.63 in Average distance: 397.34 mAverage relative humidity: 84.62 percent Average relative humidity: 81.98 percentAverage temperature: 13.06°C Average temperature: 13.52°CAverage max. sound level: 91.48 dB Average max. sound level: 92.46 dBAverage ASEL: 110.36 dB Average ASEL: 109.78 dB

Distance Average ASEL Distance Average ASEL(in) (dB) (M) (dB)

50 123.1 50 119.6100 118.8 100 116.4200 114.8 200 113.150) 110.0 500 108.3

1000 105.7 1000 104.02000 100.6 2000 98.85000 92.0 5000 89.8

10000 84.8 10000 82.1

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Table A5 Table A7

SEL vs. Distance, Set I, Averaged Over 1/4 nmi at SEL vs. Distance, Set i, at Cruise Speed, for AllCruise Speed, Jan 5, 6, Traveling East and West Distances, Jan 5, Traveling East and West

Total number averaged: 12 Total number averaged: 24Average distance: 457.20 in Average distance: 685.80 mAverage relative humidity: 92.87 percent Average relative humidity: 93.28 percentAverage temperature: 12.330 C Average temperature: 11.970 CAverage max. sound level: 94.95 dB Average max. sound level: 93.72 dBAverage ASEL: 111 .48 dB Average ASEL: 111.30 dB

Distance Average ASEL Distance Average ASEL(M) (dB) (m) (dB)

50 122.4 50 127.2100 119.2 100 122.2200 115.8 200 117.8500 110.8 500 112.81000 106.4 1000 108.32000 101.1 2000 103.05000 92.0 5000 93.8

10000 84.3 10000 85.9

Table A6 Table A8

SEL vs. Distance, Set 2, Averaged Over 1/4 nmi at SEL vs. Distance, Set 2, at Cruise Speed, for AllCruise Speed, Jan 6, Traveling East and West Distances, Jan 6, Traveling East and West

Total number averaged: 12 Total number averaged: 21Average distance: 457.20 m Average distance: 363.13 mAverage relative humidity: 74.60 percent Average relative humidity: 75.76 percentAverage temperature: 14.50'C Average temperature: 14.200 CAverage max. sound level: 89.27 dB Average max. sound level: 91.04 dBAverage ASEL: 108.14 dB Average ASEL: 108.80 dB

Distance Average ASEL Distance Average ASEL(iM) (dB) (M) (dB)

50 118.8 50 118.0100 115.6 100 114.920o 112.4 200 111.6500 107.6 500 106.8

1000 103.5 1000 102.62000 98.4 2000 97.45000 89.5 5000 88.6

10000 81.5 10000 80.8 .

21

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APPENDIX:

SEL VS. DISTANCE TABLES FOR MICROPHONES 1, 2, AND 3AVERAGED OVER VARIOUS TYPES OF OPERATIONS

/.

Table A l Table A3

Key to Appendix Tables SEL vs. Distance Averaged Over 1/2 nmi at Cruise

Table Date Speed Distance Direction Speed, Jan 5, 6, Traveling East and West

A2 Both R 1/4 Both Total number averaged: 12A3 Both (5 Jan)* R 1/2 Both Average distance: 914.40 mA4 Both t6 Jan)* R 1/8 Both Average relative humidity: 93.70 percentA5 5 Jan R 1/4 Both Average temperature: I 1.600CA6 6 Jan R 1/4 BothA7 5 Jan R All Both Average max. sound level: 92.50 dBA8 6 Jan R All Both Average ASEL: 111.12 dBA9 Both R All I-A10 Both R All W Distance Average ASELAll Both R All Both (M) (dB)A12 Both R 1/8 and 1/4 BothA13 5 Jan H 1/4 Both 50 132.0A14 6 Jan H 1/4 Both 100 125.2AIS Both H 1/4 Both 200 119.7A16 5 Jan L 1/4 Both 500 114.7Al 7 6 Jan L 1/4 Both 1000 110.3A18 Both L 1/4 Both 2000 104.9

5000 95.6I Wo .087.5

Table A2 Table A4

SEL vs. Distance Averaged Over 1/4 nmi at Cruise SEL vs. Distance Averaged Over 1/8 nmi at CruiseSpeed, Jan 5, 6, Traveling East and West Speed, Jan 5, 6, Traveling East and West

Total number averaged: 24 Total number averaged: 9Average distance: 457.20 in Average distance: 237.70 mAverage relative humidity: 83.73 percent Average relative humidity: 7730 percentAverage temperature: 13.420 C Average temperature: 13.80 0 CAverage max. sound level: 92.11 dB Average max. sound level: 93.41 dBAverage ASEL: 109.81 dB Average ASEL: 109.68 dB

Distance Average ASEL Distance Average ASEL(m) (dB) (in) (dB)

50 120.6 50 117.0100 117.4 100 113.8200 114.1 200 110.5500 109.2 500 105.7

1000 104.9 1000 101.42000 99.7 2000 96.25t)00 90.8 5000 87.310000 82.9 10000 79.8

20

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Table 3 2. The relation between operator technique and

LACV-30 Operational Noise Level vs. Distance Data noise should be constantly stressed. An "overly en- -thusiastic" type of operation creates more noise and

Cruise Speed, Maneuver is less efficient" this type of operation should beHligh Speed.* Below Flump Equivalent discouraged. Similar problems (along with comparable

Distance SEL Speed* SEL Level reductions in efficiency) are common with helicopters(m) (dB) (dB) (d) and construction equipment. The solution is stress on

SO 122.9 124.8 93.5 the importance of efficient, neighborly operation of100 118.8 121.6 87.3 the craft.200 114.9 118.3 80.8500 110.0 113.5 71.8 3. Since weather conditions play the major role in10oo0 105.7 109.2 64.3 sound propagation and the resulting loudness in the2(000 100.4 103.9 56.1

5000 91.4 94.2 44.7 community, weather and sound monitoring may beI00o00 83.5 84.9 36.2 used to adjust operations. For example, time-of-day

requirements can be pegged to measured conditions*In gencral, iust the cruise speed data should be sufficient for and time of year.all operations. In certain instances. one may need to separate-1., use the below hump speed data.

passbx measurements, levels varied by as much as 10dB from one day to the next because of sound propa-gation conditions. CONCLUSION

Potential noise mitigation methods include thefllowing: The report gives the sound exposure level vs. dis-

tance curves for the LACV-30 for various speeds and1. The prop noise can be reduced (probably 10 to operations over water and over land. These data

20 dB) by a redesigned prop and possible inclusion of supplement earlier rotary wing aircraft data developeda shroud. Since machinery noise is generally a sign by USA-CERL and used in the USA-CERL modifiedof inefficiency, a quieter prop would likely be more version of the Air Force NOISEMAP Predictionftle! effiCient. Program.

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Inland Measurements other microphones were 275 In from the center. TheMeasurements were also made at locations 4 and 5 resulting I/3-octave spectra were also corrected for an

inland. Location 4 was about 300 in inland and at additional 85 in of atmospheric absorption (tempera-roughly the same elevation as microphones 1, 2, and 3 ture and relative humidity did not change much duringwhile location 5 was 800 m inland atop a 15 m hill. the I day these data were gathered). These 1/3-octaveComparing the measured SEL at the inland micro- spectra were similar from operation to operation andphones with the corresponding composite prediction were averaged (on an energy basis) over all the opera.curves based on data gathered with the shoreline tions performed to form an overall measured equiva-microphones showed the general trend (as expected) of lent 1/3-octave spectrum at a distance of 275 m fromexcess attenuation due to propagation over ground, in the center of a maneuvering area for a maneuveringaddition to normal geometric spreading. This excess craft. This 1/3-octave spectrum (Figure 7) was con-attenuation varied between 0 and 16 dB. About 8 or verted to an A-weighted LEQ vs. distance using the

•.. 9 dB was a typical value at station 4. For station 5, methods of ANSI SI.26-1978 to vary the 1/3-octaveon a hill top. the iesults were quite mixed. In one levels in terms of atmospheric attenuation (correctinginstance for below hump speed operation, the hill- to 15°C and 70 percent relative humidity) withtop measurements actually exceeded the value pre- distance and a factor of 20 log D/Dm to vary the over-dicted by the shoreline microphones by about 3 1/2 all level with distance.dB. Since this location was on a 15-in hill, refractionout of a shadow zone may have contributed to high Table 3 contains the overall results. The secondlevels, with ground reflection less of a factor, column is the A-weighted SEL vs. distance (where

distance is point of closest approach) for a craftFor predictions of overland passby noise levels, it traveling at cruise speed or high speed on the water. the

is recommended that 8 dB be subtracted from the third column contains the below hump speed SELoverwater SEL vs. distance prediction when the land data, and the fourth column contains the equivalentsite is substantially inland and the elevation is near A-weighted level vs. distance (from the geometricsea level. When the land site has elevated terrain or the center of the maneuver area) for a craft maneuveringreceiver is at a high location, then diffraction is more on land. These data have been entered into the dataimportant than excess ground attenuation and nothing base of the INCS and are available for the developmentshould be subtracted from the overwater SEL vs. of noise zone maps by AEHA and others.distance curves.

Difrerent Speeds A NOISE SOURCES AND POTENTIAL: Comparisons were also made as a function of speed. MITIGATION METHODS

In addition to the normal cruise speed, data weregathered for high and below hump speed. Figure 7compares these three composite data sets. The below Several reasons for high noise emissions fiom thehump speed creates a slightly higher SEL than does,,.LACV-30 were identified dLIIg the coutse ot datathe cruise speed. The high speed SELs are slightly gathering and are included here as useful intornatlonlower than the cruise speed SELs. In general, over-water LACV-30 operations can probably be adequate- The measured passby levels of approxumatel. 1 10ly represented by the cruise speed composite curve, dB (A-weighted SEL) at 1/4 and 1/2 nmi indicate thisbut In critical instances one may wish to use the below is a very noisy craft. The spectra (Figure 8) show thathump composite for this mode of operation. the primary noise source is at 100 Iz, which is the

blade passage frequency of the props.Overland Maneuver Data

v The overland maneuver data were analyzed by Operator technique is also a factor in the noisefinding the equivalent 1/3-octave spectrum levels for generated by the LACV-30. at least over land. Duringthe entire maneuver. Because microphone 5 was on a the maneuver tests, the second operator moved the

" " hill and closer to the center of the array than micro- craft more quickly but with less control than did thephones I through 4. 3.1 dB were subtracted from first, taking longer to perform the maneuvet indmicrophone 5's spectrum to make it equivalent (in creating higher noise peaks.terms of distance) to the other four spectra. The3.1 -dB figure was calculated as 20 log 275/192 since Weather conditions play a major role m the noisethe hill position was 192 in from the center while the which propagates from the LACV-30. l)urmng the

16

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1*

.

USA-CERL True Integrating Nagra DJEnvironmental Noise Monitor Tape Recorderand Sound Exposure LevelMeter

Figure S. Measurement equipment at a site.

- contrast t) 2 seconds for aircraft) was used because of passbys. The data were gathered on two consecutive- the LACV-30's slow speed and long passby time days. Sound propagation from ship to shore was much" compared to aircraft speed.* Each measured SEL and stronger on the first day than the second, resulting in

1/3 octave spectrum was then developed into an SEL higher sound levels recorded on the first day. On thevs. distance curve using three factors. These factors first day, readings were also taken 1/2 nmi from shorewere the l/3-octave band absorption values in ANSI and on the second day 1/8 nmi from shore.SI .26-1978,6 the factor for the spherical spreading ofsound (20 log D/Dm where D is the distance in ques- Except for the measurements made at 1/2 nmi thetion and Dm is the measurement distance), and the first day, the general results were fairly consistent fromfactor 10 log (Dm/D) to account for the duration one distance and day to the next. On the first day,change in SEL with distance. however, sound propagation conditions were such that

Shoreline Measurements the measurements made at 1/2 nmi were virtuallyThe various site and distance data were arrayed for identical to the results at 1/4 nmi; there was no change

a given operation, such as normal power cruise. As with distance.indicated above, primary use was made of data gather.ed by the three shoreline microphones and the 1/4 nmi The appendix tabulates various SEL vs. distance

combinations calculated. Figure 6 illustrates thecomposite SEL vs. distance for 1/4 and 1/8 nmi,

*The data were also analyzed using a 1/2-second time calculated using microphones 1,2, and 3, during cruiseperiod. Using this very short time only resulted in changes of a speed on the first and second day. Figure 6 also shows rfew tenths of a decibel in the SEL vs. distance curves (Appen-dix). just the l/2-nmi data and a composite of all the cruise

'American National Standard Institute (ANSI) Standard speed data. The l/2-nmi data raise the composite

S1.26-1978, "Method for the Calculation of Absorption of average by 2 to 3 dB over what it would otherwise be.Sound by the Atmosphere." These data were included since they were valid.

14

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Start and End at Center I* 1 Figur Between Dunes

• ~"Figure 8" ;'Y

Loop"

Figure 4. Land maneuver patterns for the LACV-30

N

Table 2

Overland Maneuvers

Run No.* Set No. Maneuver**

33 3 "Fig. 8"34 3 "Fig. 8"35 3 2-loop36 3 2-loop37 4 2-loop38 4 2-loop39 4 "Fig. 8'"

*A typical land maneuver took 15-20 minutes**See Figures 3 and 4 for definition of land maneuvers

13

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Table I

Overwater Passby Operations

a. Set I, MP Station. 5 Jan 84

DistanceRun No. Direction (nmi) Speed*

I W 1/4 R2 E 1/4 R".:

3 W /4 1/4 R

5 E 1/4 L t76 W 1/4 L7 E 1/4 L

.8 W 1/4 L .- 1

9 E 1/4 H j10 W 1/4 H11 L 1/4 H12 W 1/4 H

13 E 1/2 R14 W 1/2 R15 E 1/2 R16 W 1/2 R

b. Set 2, MP Station, 6 Jan 84

17 E 1/4 R18 W 1/4 R19 E 1/4 R

20 W 1/4 R

21 E 1/4 L22 W 1/4 L23 E 1/4 L24 W 1/4 L

25 E 1/4 H26 Aborted -

27 E 1/4 H28 W 1/4 H

29 E 1/4 H30 W 1/8 R31 E 1/8 R32 W 1/8 R

•R cruise speed

L = below hump speedH = high speed

I].?

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11 "'-

CERIL I)IS'i'RBU'ITON

Chtoe rt KuietrsATTNI Tech Honitor INSCOM - Ch, Intt. Div

ATTN& DAIN-ASI-L (2) ATTN& Facilittee Engineer (3)

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WESTCON.

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- . . . . . ... . - . .. - . . . . --. -, %.e '

ENA Team Distribution I"

Chief of Engineers 6th US Army 94129 Federal Highway Administration 22201ATTN: OAEN-ECC-E ATTN: AFKC-EN Region 15ATTN: OAEN-ECE-8ATTN: DAEN-ECE-I (2) 7th Army Combined Arms Teng. Cntr. 09407 NASA 23365 (2)ATTN: OAEN-ZCF-B ATTN: AETTh-HRD-EHDATTN: DAEN-ECZ-A National Bureau of Standards 20234ATTN: OAEN-ZCE-O (2) Armament & Dev. Command 21005

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V -* *-.%* *- * *."* *.. . . . . ..".

FILMED

* 7-85

DTIC