| On the Effect of a Transverse Acoustic Field on a Flush Shear Coaxial Injector |
13-Jul-2009 |
15 pages |
| Authors:
Douglas Talley; Juan I Rodriguez; Ivett A Leyva; Jeffrey J Graham; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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 | An experimental study on the effects of an externally-imposed transverse acoustic field in a flush shear coaxial jet is presented. In this case the inner jet recess is zero and both the inner and outer jet exit planes coincide. Since recess is a design variable used when designing new injectors, this study complements previous studies from this group where the injector geometries included a recess. The shear coaxial injector used ... |
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| Human Bioresponse to Low-Frequency Underwater Sound |
02-Feb-2009 |
240 pages |
| Authors:
Mark F Hamilton; Sarah L Gourlie; Paul A Waters; TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
|
| A technical summary of work completed under contract N00014-06-1-0299, entitled Human Bioresponse to Low-Frequency Underwater Sound, is given. Preliminary research such as the development of two micromechanical models of lung tissue and the calculation of elastic constants based upon such models is described. Progress made in the development of a lumped-element model of the human body and its internal organs is discussed. Master's theses completed under this contract are attached. ... |
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| Generic Design Procedures for the Repair of Acoustically Damaged Panels |
Dec-2008 |
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| Authors:
R J Callinan; C H Wang; S Sanderson; S C Galea; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AIR VEHICLES DIV
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 | Acoustic fatigue is the result of high frequency lateral vibration of an aircraft panel due to time varying pressure waves caused by engine and/or aerodynamic effects. For example, acoustically induced cracks have been recorded in the lower external surface of the nacelle skin of the F/A-18 aircraft and aft fuselage. In the case of the inlet nacelle overall sound pressure levels of the order of 172 dB have been recorded. ... |
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| Effect of the New Insulation Liner on Noise Levels in the CH124B (Sea King) Aircraft |
Nov-2008 |
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| Authors:
Bernadette Quemerais; DEFENCE RESEARCH AND DEVELOPMENT TORONTO (CANADA)
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| Crew members of the CH124B (Sea King) helicopter are exposed to elevated noise levels. To minimize noise levels as well as to insulate electrical wiring, the Sea King is equipped with a liner, which reduces noise. Recently the Sea King helicopters have been equipped with a new type of liner. Defence Research and Development Canada (DRDC) Toronto was asked to verify the noise levels in the Sea King during flight ... |
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| Ignition Characteristics of Single-Walled Carbon Nanotubes (SWCNTs) Utilizing a Camera Flash for Distributed Ignition of Liquid Sprays (Preprint) |
Oct-2008 |
8 pages |
| Authors:
S A Danczyk; B Chehroudi; C Morgan; Alan Badakhshan; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
|
| We have studied ignition characteristics of SWCNTs with an ordinary camera flash. Our ultimate goal is to use SWCNTs as a means for ignition of liquid rocket fuel sprays. Based on the initial results, we believe this approach enables volumetric and distributed ignition of fuel sprays. Our preliminary investigation was concentrated on the effects of two different incident light source pulse widths on minimum ignition energy (MIE) from 350-1500 nm, ... |
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| Effects of Noise and Tonal Stimuli on Hearing in Pinnipeds |
Jan-2008 |
6 pages |
| Authors:
Colleen Reichmuth; CALIFORNIA UNIV SANTA CRUZ INST OF MARINE SCIENCES
|
| The practical objective for FY08 was to complete behavioral testing with three subjects against an equal energy matrix of tonal noise exposures (with similar characteristics to mid-frequency sonar) based on pre-determined combinations of stimulus duration and received sound pressure level. The specific aims were (1) to compare the characteristics of the threshold shifts induced by exposure to tonal sounds to the auditory effects induced by broadband noise exposure so that ... |
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| Beaked Whale Anatomy, Field Studies and Habitat Modeling |
NOV 2007 |
43 pages |
| Authors:
John A. Hildebrand; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE PHYSICAL LAB
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| This report describes the results of two tasks related to the study of beaked whales. The first study was a field study of beaked whales in the Gulf of California from December 2004 to December 2006. The goal of the study was to determine the range of sound produced by beaked whales and to investigate beaked whale behavior and habitat. A minimum of 17 cetacean species (12 toothed and 5 ... |
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| Reverberation Time, Feasibility for Weapons Fire Range Estimation |
OCT 2006 |
20 pages |
| Authors:
Brad Libbey; ARMY NIGHT VISION LAB FORT BELVOIR VA
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| Localization of an acoustic blast source in urban battle spaces is frequently complicated by multiple arrivals resulting from reflections within the acoustic environment. Temporal windowing can be used to isolate the direct arrival in situations where a direct path between source and receiver exist. However, if the source is located around a corner from a receiver the first arrival would lead to an erroneous source location estimate. These complications have ... |
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| Sound Attenuation from Earmuffs and Earplugs in Combination: Maximum Benefits vs. Missed Information |
Sep-2006 |
7 pages |
| Authors:
Patricia Odell; Sharon M Abel; DEFENCE RESEARCH AND DEVELOPMENT TORONTO (ONTARIO) JUDGEMENT AND DECISION-MAKING GROUP
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| High noise levels from aircraft, small and large caliber weapons, land vehicles, ships, or submarines are characteristic of military operational environments. Continuous levels in the interior of fixed or rotary wing aircraft or in the vicinity of jet engines range from 100 - 130 dBA (15,18). Peak sound pressure levels from impulse noise produced by a howitzer may be as high as 180 dB SPL (28). Small caliber weapons such ... |
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| Investigation of Passive Control Devices for Potential Application to a Launch Vehicle Structure to Reduce the Interior Noise Levels During Launch |
25 MAY 2006 |
87 pages |
| Authors:
Carl Q. Howard; Colin Hansen; ADELAIDE UNIV (AUSTRALIA) DEPT OF MECHANICAL ENGINEERING
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| This series of reports document a multi-year research project into the reduction of acoustic vibrations in space launch vehicles using passive mass damping devices. The purpose of this report is to collate all the knowledge that has been gained during all four stages, into a single concise document. |
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| Continued Investigation of Immune Competence in Navy Marine Mammals: Implications for Health Viability and Mission Readiness |
JAN 2006 |
5 pages |
| Authors:
Tracy Romano; MYSTIC AQUARIUM AND INST FOR EXPLORATION CT
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| Deployed Navy dolphins are exposed to infectious agents and pollutants in environments that may compromise their health and system mission. Challenges dolphins experience during deployments include: transport to different time zones, changes in water temperature, contaminated water, varying acoustic levels, and exposure to wild marine mammal populations. These challenges (confinement/restraint, thermal stress, pollutants, and auditory stress) have been shown to cause immunosuppression in other manuals. Our laboratory has developed and ... |
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| Evaluation of Matched-Field Processing Techniques Using Simulated Acoustic Vector Sensor Data |
DEC 2005 |
91 pages |
| Authors:
Yu-Chih Hsu; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| There has recently been growing interest in the use of acoustic particle velocity measurements for sonar system applications such as source localization. It is expected that acoustic particle velocity sensors or "vector" sensors have the potential to improve the performance of scalar acoustic pressure sensors. Although extensive research has been performed to study the enhancements for plane-wave beamforming, little has been done in the more general area of matched-field processing. ... |
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| Evaluation of Acoustic Propagation Paths into the Human Head |
25 JUL 2005 |
23 pages |
| Authors:
William D. O'Brien Jr.; Yuhui Liu; ILLINOIS UNIV AT URBANA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| The overall goal of this research was to develop an acoustic wave propagation model using well-understood and documented computational techniques that track and quantify an air-borne incident acoustic wave propagated around, into and in the human head. The model purpose served two purposes: (1) determine alternate acoustic propagation paths to the cochlear shell that exist besides the normal air-borne acoustic propagation path (eardrum-ossical path) through the auditory canal and (2) ... |
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| Reflection of Microwave Pulses From Acoustic Waves: Summary of Experimental and Computational Studies |
31 MAY 2005 |
30 pages |
| Authors:
G. M. Kepler; R. A. Albanese; H. T. Banks; V. A. Bokil; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| In [1, 4], the authors proposed and analyzed an interrogation (inverse problem) methodology based on use of an acoustic wave as a reflecting virtual interface for propagating impulses. It is by now well accepted (e.g., see [2, 7, 11, 14]) that acoustic pressure waves will interact with electromagnetic signals in ways that often mimic interfacial partial reflection/partial transmission for the electromagnetic waves. The response of atomic electrons to an applied ... |
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| Investigating Double Hearing Protection using Human Subjects |
APR 2005 |
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| Authors:
Christopher Tubb; Susan Mercy; Soo James; QINETIQ FARNBOROUGH (UNITED KINGDOM) HUMAN FACTORS IN ACOUSTICS AND VIBRATION
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| With the growing need to protect the hearing of military personnel, the use of double protection, earplugs and earmuffs used in combination, has become more and more prevalent. Furthermore Active Noise Reduction (ANR) headsets and earplugs appear to offer a means of increasing the attenuation of these double protection systems. However, it has been shown that the attenuation afforded by double protection is not a simple additive process; the combined ... |
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| Equations for Finite-Difference, Time-Domain Simulation of Sound Propagation in Moving Inhomogeneous Media and Numerical Implementation |
FEB 2005 |
16 pages |
| Authors:
Vladimir E. Ostashev; D. K. Wilson; Lanbo Liu; David F. Aldridge; Neil P. Symons; NEW MEXICO STATE UNIV LAS CRUCES DEPT OF PHYSICS
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| Finite-difference, time-domain (FDTD) calculations are typically performed with partial differential equations that are first order in time. Equation sets appropriate for FDTD calculations in a moving inhomogeneous medium with an emphasis on the atmosphere! are derived and discussed in this paper. Two candidate equation sets, both derived from linearized equations of fluid dynamics, are proposed. The first, which contains three coupled equations for the sound pressure, vector acoustic velocity, and ... |
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| A Computational and Statistical Framework for Multidimensional Domain Acoustooptic Material Interrogation |
18 JAN 2005 |
47 pages |
| Authors:
H. T. Banks; V. A. Bokil; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| We consider an electromagnetic interrogation technique in two and three dimensions for identifying the dielectric parameters (including the permittivity, the conductivity and the relaxation time) of a Debye medium. In this technique a travelling acoustic pressure wave in the Debye medium is used as a virtual reflector for an interrogating microwave electromagnetic pulse that is generated in free space. The reflections of the microwave pulse from the air-Debye interface and ... |
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| Parameter Identification for Dispersive Dielectrics Using Pulsed Microwave Interrogating Signals and Acoustic Wave Induced Reflections in Two and Three Dimensions |
JUL 2004 |
121 pages |
| Authors:
H. T. Banks; V. A. Bokil; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| In this report we consider an electromagnetic interrogation technique for identifying the dielectric parameters of a Debye medium in two and three dimensions. These parameters include the dielectric permittivity, the conductivity and the relaxation time of the Debye medium. In this technique a travelling acoustic pressure wave that is generated in the Debye medium is used as a virtual reflector for an interrogating microwave electromagnetic pulse that is generated in ... |
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| Environmental Mitigation Ranges around Australia |
FEB 2004 |
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| Authors:
Paul Clarke; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION EDINBURGH (AUSTRALIA) MARITIME OPERATIONS DIV
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| URS Australia is currently writing "Environmental Management Plan for Australian Maritime Exercise Areas" for the ADF. To help URS, the MOD within DSTO has modeled the expected received sound pressure levels for a number of different environments and sonar frequencies around Australia. The maximum ranges the sound pressure levels dropped below 182 and 160 dB were then calculated for a number of different sonars operating at levels indicative of or ... |
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| iMAST Quarterly, Number 1, 2004 |
Jan-2004 |
9 pages |
| Authors:
APPLIED RESEARCH LABORATORY STATE COLLEGE PA
|
| This quarterly briefly addresses engine fretting evaluation. The feature article is titled Light Armored Vehicle Noise Control. Exploiting the acoustics expertise resident at ARL Penn State, engineers were asked by the Marine Corps to address noise issues related to the Light Armored Vehicle. The integration of advanced materials, manufacturing processes, health monitoring, and acoustic tailoring promotes reductions in gross weight, vibration, interior noise, and life-cycle cost, as well as increases ... |
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| Leading Edge Noise from Thick Foils in Turbulent Flows |
SEP 2003 |
45 pages |
| Authors:
Jonathan Gershfeld; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
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| The prediction of dipole sound from the diffraction of turbulence by the leading edge of a thick foil is made with the Kirchhoff integral for rigid surface scattering of the stagnation enthalpy. The incident field is determined from a volume integral and the rigid plane Green function using an equivalent form of Howe's (1975) acoustic analogy that is derived in terms of the mean free stream velocity and the fluctuating ... |
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| A Comparison of the Underwater Acoustic Performance of Single Crystal vs. Piezoelectric Ceramic based Cymbal Projectors |
Sep-2003 |
9 pages |
| Authors:
James F Tressler; Thomas R Howarth; Dehua Huang; NAVAL RESEARCH LAB WASHINGTON DC
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| The underwater acoustic performance of three same-design cymbal based electro-acoustic projectors are compared. Two of these projectors contain PMN-PT single crystal piezoelectric as the active material while the third utilizes conventional PZT-5H piezoelectric ceramic. The units containing the single crystal material show an improvement in the acoustic source level anywhere from 3 to 15 dB over the frequency band 1-25 kHz. The higher source level is a consequence of the ... |
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| Highly Directive Underwater Acoustic Receiver |
22 JUL 2003 |
15 pages |
| Authors:
Benjamin A. Cray; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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| An underwater acoustic receiver sensor is disclosed that measure up to seven (7) quantities of acoustic field at a collocated point. The quantities measured by the acoustic receiver sensor are acoustic pressure, three orthogonal components of acoustic particle acceleration and three spatial gradients of the acceleration vector. These quantities are appropriately combined and provides for improved directivity of the acoustic receiver sensor. |
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| Acoustic Absorption Measurements for Characterization of Gas Mixing |
14 MAY 2003 |
10 pages |
| Authors:
Aurelien Cottet; Lei Wu; Andrew Meyers; David Scarborough; Tim Lieuwen; GEORGIA INST OF TECH ATLANTA
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| This paper demonstrates the use of acoustic absorption measurements to characterize the level of molecular mixing between gaseous mixtures. This objective is motivated by the observation that many existing methods only quantify macro-scale entrainment. Over a large range of frequencies, acoustic damping is dominated by vibrational relaxation processes. Our approach takes advantage of the fact that the relaxation frequency for a particular gas is often a strong function of the ... |
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| Improved Performance of Lean-Burn Combustion |
APR 2003 |
34 pages |
| Authors:
R. P. Lindstedt; J. H. Whitelaw; IMPERIAL COLL CONSULTANTS LTD LONDON (UNITED KINGDOM)
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| The focus of the research described here is on establishing and controlling the causes of combustion instabilities in fuel lean combustion systems. The frequencies of the dominant instability modes are typically < 500 Hz and a comprehensive closure at second moment level, which accounts for the effects of persistent non-gradient transport in a consistent manner, has been applied to compute the combusting flow characteristics in the plane duct configuration of ... |
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| Reconsideration of the Effects of Impulse Noise (Reexamen des Effects du Bruit Impulsionnel) (CD-ROM) |
Apr-2003 |
|
| Authors:
NATO RESEARCH AND TECHNOLOGY ORGANIZATION NEUILLY-SUR-SEINE (FRANCE)
|
| ELECTRONIC FILE CHARACTERISTICS: 126 files; HyperText Markup Language (.HTML), Adobe Acrobat (.PDF), and .GIF image. PHYSICAL DESCRIPTION: 1 computer laser optical disc (CD-ROM); 4 3/4 in.; 90.6 MB. SYSTEMS DETAIL NOTE: IBM-clone PC-compatible; Adobe Acrobat Reader included on disc. ABSTRACT: This report contains the main outcome of the work constituted by NATO Research Study Group RSG.29 Reconsideration of the effects of impulse noise. The main objective of the work of ... |
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| Intensity Probe 02-20 Using Miniature Hollow Spheres |
JAN 2003 |
17 pages |
| Authors:
David J. Van Tol; Gerald C. Lauchle; Thomas B. Gabrielson; PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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| A probe is designed to measure the acoustic intensity at the primary frequencies (20-30 kHz) of a parametric array. It is designed to operate at depths up to 61 m with a pressure sensitivity of less than -235dB re 1V/mPa while not disturbing the acoustic field of interest. Higher sensitivity would result in saturation when exposed to the expected sound pressure levels. The sensitivity and depth requirements were met, while ... |
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| An Acoustic Procedure for Measuring Blade-Frequency Forces Generated by Model Ship Propellers |
DEC 2002 |
13 pages |
| Authors:
M. Strasberg; NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD
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| An acoustic procedure is described for measuring the blade-frequency fluctuating forces developed by a powerful model propeller operating behind a model of a ship's hull or a wake generator in the anechoic test section of a wind tunnel. The sound pressure radiated by the propeller in a given direction is measured and its magnitude inserted into a simple theoretical relation to determine the alternating force developed by the propeller in ... |
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| Analysis of a Fluid-Loaded Thick Plate |
01 OCT 2002 |
42 pages |
| Authors:
Andrew J. Hull; NAVAL UNDERSEA WARFARE CENTER NEWPORT DIV RI
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| The physics of a thick plate with fluid loading on both sides provides the theoretical basis for insertion loss and echo reduction tests, both of which are typically used to determine how efficiently a material transmits or reflects energy. Such testing is conducted by insonifying a submerged, slab- shaped sample and then measuring the transmitted and reflected sound pressure. Based on the sound pressure level of the incident field, the ... |
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| A Model of the Acoustic Intensity Field Generated by a Multi-Engine Turbo-Prop Aircraft |
SEP 2002 |
57 pages |
| Authors:
Brian S. Davis; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN EFFECTIVENESS DIRECTORATE
|
| High levels of noise within the fuselage of a turbo-prop aircraft cannot be mitigated by traditional acoustic coating techniques, since the primary frequencies are generally less than 500 Hz. Tests of an advanced device, designed to control the relative phase between the engines, identified 10-20 dB reductions in the acoustic noise levels within the fuselage. An analytical framework was developed to model the observed effects independent of airframe design. The ... |
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| Calibration, Measurement, and Voltage Output of Velocity Hydrophones |
15 JUL 2002 |
16 pages |
| Authors:
Tien-Chay Chen; NAVAL UNDERSEA WARFARE CENTER NEWPORT DIV RI
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| This report discusses how to calibrate velocity hydrophones using a standard pressure hydrophone and investigates the relative contributions by the pressure and particle velocity to the measured sensitivity of such hydrophones. Sections 2 and 3 deal with the issues associated with velocity hydrophone calibration using a standard pressure hydrophone and the required correction factor for sensitivity calibration in a spherical wavefront. Section 4 summarizes the particle velocity's voltage contribution to ... |
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| Noise Attenuation in HALO Vertical Wind Tunnel Training |
JUL 2002 |
27 pages |
| Authors:
Dale A. Ostler; Paul A. Cain; Elmaree Gordon; Eric W. Fallon; ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
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| The Vertical Wind Tunnel (VWT) at Ft. Bragg, NC is one of the Army's training grounds for High Altitude Low Opening (HALO) parachute jumpers. Due to the nature of the operation (i.e., jet engine and high wind stream) personnel using the VWT are exposed to steady-state noise levels in excess of 120 dBA SPL (sound pressure level). These levels exceed the safe noise exposure limits stipulated in DA PAN 40-501 ... |
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| Impulse Noise Levels of the UH-60A/L Black Hawk Helicopter Cockpit Air Bag System - Enhanced Lateral Air Bags |
JUL 2002 |
31 pages |
| Authors:
William A. Ahroon; Elmaree Gordon; Frederick T. Brozoski; ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
|
| A Cockpit Air Bag System (CABS) is being developed for the UH-60A/L Black Hawk helicopter. Earlier aeromedical evaluations of CABS revealed a potential injury risk associated with the lateral air bag component. An enhanced lateral air bag was developed and a series of 12 deployment tests was conducted. Impulse noise levels ranged from 144.8 dB peak sound pressure level (SPL) to 162.4 dB peak SPL with B-durations up to 172.6 ... |
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| Recreation Diver Responses to 600-2500 Hz Waterborne Sound |
13 JUN 2002 |
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| Authors:
D. M. Fothergill; D. S chwaller; S. E. Forsythe; E. A. Cudahy; NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
|
| Increasing use of high-powered sonar for detection of submarine has put the recreational diver at an increased risk of sound injury. In particular the development of new sonar systems for use in littoral waters raises the possibility that high levels of underwater sound may encroach on popular recreational dive sites. Currently, there is no guidance to indicate acceptable sound exposure levels for sonar systems that operate in the 500 2500 ... |
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| Recreational Diver Responses to 600-2500 Hz Waterborne Sound |
13 JUN 2002 |
61 pages |
| Authors:
David M. Fothergill; Derek Schwaller; S. E. Forsythe; Edward A. Cudahy; NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
|
| Previous work (UHM, 27( Suppl): 18, 2000) investigated aversion to 600-2500 Hz waterborne sound (WBS) in US Navy divers. This study extends previous work by investigating the effects of 600-2420 Hz WBS on psychophysical and reaction time responses of recreational divers who have never previously experienced high levels of WBS. Nineteen male and two female military recreational divers volunteered. Subjects wore full 3-mm wet suits (without hood or gloves). Sound ... |
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| A High Intensity Infrasonic Acoustic Test System |
NOV 2001 |
64 pages |
| Authors:
H. E. Boesch Jr.; Christian G. Reiff; Bruce T. Benwell; ARMY RESEARCH LAB ADELPHI MD
|
| We describe the design, mathematical modeling, construction, and test of an acoustic test system intended to support the performance of high-intensity acoustic effects experiments on large targets at low-sonic to infrasonic frequencies. An early experimental version of the system, HILF1, used a compressed-air source and airflow modulator from the ARL Mobile Acoustic Source (MOAS) and a single-volume Helmholtz resonator test chamber to achieve sound pressure levels (SPL) above 140 dB ... |
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| Large Eddy Simulation of a Supersonic Cavity Flow with an Unstructured Grid Flow Solver |
AUG 2001 |
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| Authors:
Brian R. Smith; LOCKHEED MARTIN AERONAUTICS CO FORT WORTH TX
|
| Large Eddy Simulation methods were implemented in a hexahedral based unstructured grid flow solver and tested for the analysis of transonic flow over an open cavity. This approach was developed for efficient application of Computational Fluid Dynamics methods to the highly unsteady flows in a geometrically complex weapons bay. A compressible sub grid scale model was implemented. The compressible flow solver uses an upwind flux difference splitting scheme. A Mach ... |
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| Direct Numerical Simulations of High Speed Flow Over Cavity |
AUG 2001 |
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| Authors:
A. Hamed; D. Basu; A. Mohamed; K. Das; CINCINNATI UNIV OH DEPT OF AEROSPACE ENGINEERING AND ENGINEERING MECHANICS
|
| Direct numerical simulations are used to investigate the effect of Mach number on the unsteady flow of an open cavity. The implicit solution is obtained for the compressible Navier-Stokes Equations using compact sixth-order spatial differencing coupled with tenth-order implicit filters. Results for transonic and subsonic flow over a two dimensional cavity are presented for the sound pressure level and pressure fluctuation frequencies. |
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| Acoustically Enhanced Paint Application |
30 JUL 2001 |
15 pages |
| Authors:
Anthony A. Ruffa; DEPARTMENT OF THE NAVY WASHINGTON DC
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| The present invention is a method of coating a substrate. First, a layer of liquid polymeric coating having a pigment and a solvent is applied to the substrate. An ultrasonic acoustic source is then provided and operated at a frequency of from about above 40 kHz to provide an acoustic pressure field and an acoustic pressure of above 190 dB and directing the main lobe of the acoustic pressure field ... |
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| A Theoretical and Experimental Investigation of Acoustic Dyadic Sensors |
25 JUL 2001 |
57 pages |
| Authors:
Manuel T. Silvia; SITTEL CORP OJAI CA
|
| This report sets the groundwork for a generalized theory of directional sensors using the Taylor series of the acoustic pressure; it moves from the basic pressure sensor to the vector sensor, on to the dyadic sensor, then on to higher-order sensors depending on the number of terms in the Taylor series. A benefit of higher-order sensors is improvement in the 3-dB beamwidth; 105 degrees for a vector sensor, 65 degrees ... |
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| A Computational Model for Sound Field Absorption by Acoustic Arrays (revision 6) |
24 JUL 2001 |
20 pages |
| Authors:
H. T. Banks; D. G. Cole; K. M. Furati; K. Ito; G. A. Pinter; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
|
| In this paper, the authors discuss the sound absorption property of arrays of micro-acoustic actuators at a control surface. They use the wave equation over the half plane for the velocity potential with a boundary dissipation by a proportional pressure feedback law along the half plane boundary. The feedback gain over the array is described by a distributed shape function. They develop a computational method based on the Fourier transform ... |
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| Large Eddy Simulation for the Analysis of Weapons Bay Flows |
29 JUN 2001 |
62 pages |
| Authors:
Brian R. Smith; Tracy J. Welterlen; Neal D. Domel; LOCKHEED MARTIN AERONAUTICS CO FORT WORTH TX
|
| Computational methods for analysis of weapons bay acoustics and weapons separation were developed. Methods were developed for and implemented in Splitflow a Cartesian based unstructured grid computational fluid dynamics flow solver. Using a Large Eddy Simulation model a variety of flux discretization approaches were investigated. Moving grid and six degree of freedom dynamics capability were implemented in the parallel processing version of Splitflow. Methods for interfacing multiple Splitflow solutions separated ... |
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| Remote Ultrasonic Classification of Fluids Using the Acoustic Resonance Characteristics of the Container |
04 JUN 2001 |
|
| Authors:
Dipen N. Sinha; Gregory Kaduchak; Michael J. Keleher; LOS ALAMOS NATIONAL LAB NM
|
| A novel technique for classifying fluids in sealed, metal containers at large stand-off distances has been developed. It utilizes a recently constructed air-coupled acoustic array to excite the resonance vibrations of fluid-filled vessels. The sound field from the array is constructed by transmitting a high frequency modulated carrier wave which is parametrically sell-demodulated along its propagation path in air. The array has a narrow beam width and an operating bandwidth ... |
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| Active Control of Supersonic Impinging Jets |
JUN 2001 |
10 pages |
| Authors:
A. Krothapalli; R. Elavarasan; F. Alvi; C. Shih; FLORIDA STATE UNIV TALLAHASSEE DEPT OFMECHANICAL ENGINEERING
|
| Experimental studies of supersonic impinging jet flows suggest that they are greatly influenced by the flow-acoustic interactions through a feedback mechanism. The self-sustained oscillations of the jet column observed in theses flows result in high velocities in the ambient medium induced by the large-scale coherent vortical structures in the jet shear layers. As a consequence, the suck down force on the surface from which the jet is issuing can reach ... |
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| Active Control of Combustion Instabilities in Gas Turbine Engines for Low Emissions. Part II: Adaptive Control Algorithm Development, Demonstration and Performance Limitations |
JUN 2001 |
14 pages |
| Authors:
Andrzej Banaszuk; Youping Zhang; Clas A. Jacobson; UNITED TECHNOLOGIES RESEARCH CENTER EAST HARTFORD CT
|
| We present results of experiment with two distinct extremum-seeking adaptive algorithms for control of combustion instability suitable for reduction of acoustic pressure oscillations in gas turbine over large range of operating conditions. The algorithms consists of a frequency tracking Extended Kalman Filter to determine the in-phase component, the quadrature component, and the magnitude of the acoustic mode of interest, and a phase shifting controller with the controller phase tuned using ... |
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| Lightweight Low Frequency Loudspeaker for Active Noise Control |
02 MAR 2001 |
31 pages |
| Authors:
Robert D. Corsaro; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| The invention described herein is a low-mass, light-weight sound generator with particularly good performance at mid and low audio frequencies. It is expected to find principal use in applications where mass is of crucial importance. It is capable of delivering the high acoustic levels, as required for sound generation or active sound control. The present invention uses a generally planar acoustic membrane as a diaphragm, the diaphragm being in tension ... |
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| Analytical Study of the Noise Generated by a Coanda Wall Jet CirculationControl Device |
01 OCT 2000 |
35 pages |
| Authors:
Michael S. Howe; BOSTON UNIV MA COLL OF ENGINEERING
|
| An analysis is made of the production of sound by a hydrofoil with a Coanda wall jet circulation control (CC-) device. Three principal sources of the radiation are identified: very low frequency "curvature noise" generated by the interaction of boundary layer turbulence with the rounded trailing edge of the hydrofoil; higher frequency sound produced at the Coanda jet slot. The latter includes "passive slot noise" caused ... |
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| Nonlinear Random Response of Composite Panels in an Elevated Thermal Environment |
OCT 2000 |
54 pages |
| Authors:
C. Mei; J. M. Dhainaut; B. Duan; S. M. Spottswood; H. F. Wolfe; OLD DOMINION UNIV NORFOLK VA
|
| Sonic fatigue is being considered as one of the major design parameters for the new generation of high-speed flight vehicles. Efficient and accurate analysis methods for predicting nonlinear random response and estimating fatigue life of surface panels are urgently needed. A brief review of the various analysis methods for nonlinear random vibrations of aircraft surface panels is given. An efficient element finite modal formulation is presented for the prediction of ... |
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| Numerical Study of Wave Propagation in a Non-Uniform Flow |
SEP 2000 |
27 pages |
| Authors:
Alex Povitsky; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
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| The propagation of acoustic waves originating from cylindrical and spherical pulses, in a non-uniform mean flow, and in the presence of a reflecting wall is investigated by Hardin and Pope approach using compact approximation of spatial derivatives. The 2-D and 3-D stagnation flows and a flow around a cylinder are taken as prototypes of real world flows with strong gradients of mean pressure and velocity. ... |
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| Non-Auditory Damage Risk Assessment for Impulse Noise |
SEP 2000 |
8 pages |
| Authors:
Daniel L. Johnson; BRUEL BERTRAND JOHNSON ACOUSTICS PROVO UT
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| This paper discusses the non-injury thresholds established for three different complex waveforms. These animal studies were accomplished by EG&G at the Blast overpressure Test Site at Kirtland AFB in New Mexico. Human volunteer studies were also performed. The human studies verified non-injury levels for three different freefield waveforms and one complex waveform. The use of the Bowen model developed nearly 40 years earlier, as well as two later models, will ... |
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Reports by Keyword(s)
SOUND PRESSURE
