| Underwater Acoustic Generator Phase 2 Sea Trial, March 1992 |
AUG 93 |
|
| Authors:
R. Alksne; MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA)
|
 | In support of a joint ALO-SA, DSTO, and Industry program to develop a discrete low frequency towed underwater acoustic generator (UAG), a series of sea trials were conducted. These trials were conducted in the Gulf of St. Vincent and the sea west Of Kangaroo Island to check the environmental and acoustic performance of a concept UAG. This report describes the UAG Phase 2 evaluation trial held in March 1992. Details ... |
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| Applications of Bispectral Analysis |
AUG 93 |
50 pages |
| Authors:
A. M. Richardson; W. S. Hodgkiss; SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA MARINE PHYSICAL LAB
|
 | Estimates of the power spectral density have been found to be very useful in a variety of signal processing applications over the last several decades. Higher order spectral contain information not present in the power spectrum and recently, estimates of higher order spectral have been shown to be useful in certain signal processing problems. In particular, estimates of the bispectrum and bicoherence have been found useful in detecting non-Gaussianity and ... |
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| Active Control of Acoustic Pressure Fields Using Smart Material Technologies |
JUN 93 |
|
| Authors:
H. T. Banks; R. C. Smith; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
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| An overview describing the use of piezoceramic patches in reducing noise in a structural acoustics setting is presented. The passive and active contributions due to patches which are bonded to an Euler-Bernoulli beam or thin shell are briefly discussed and the results are incorporated into a 2-D structural acoustics model. In this model, an exterior noise source causes structural vibrations which in turn lead to interior noise as a result ... |
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| Updated Computer Programs for Predicting Single Event Aircraft Noise Data for Specific Engine Power and Meteorological Condition |
07 APR 93 |
113 pages |
| Authors:
Henry T. Mohlman; DAYTON UNIV OH RESEARCH INST
|
| This report documents OMEGA 10.8 program and OMEGA 11.3 program. These programs were developed to prepare flight and ground run-up noise data for input to NOISEMAP, the Air Force community noise exposure prediction program. All subroutines are documented at a level useful to a programmer working with the code or a reader interested in a general overview of a specific subroutine. The OMEGA 10 program inputs reference flyover datasets from ... |
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| Three-Dimensional Finite Element Model of a High Power, Low Frequency Ring-Shell Flextensional Sonar Transducer |
DEC 92 |
88 pages |
| Authors:
Rogerio N. Pinto; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| A three-dimensional finite element model of a high power, low frequency ring-shell flextensional transducer (Sparton of Canada, Ltd. Model 34A0610 was developed for use with the ATILA code. This transducer model is to be coupled with an analytical acoustic field description in order to model a dense sonar array of US Navy interest. The three-dimensional model was derived from a two-dimensional model provided by the Naval Undersea Warfare Center. Two ... |
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| Acoustical Scattering From Atmospheric Turbulence |
DEC 1992 |
14 pages |
| Authors:
Harry J. Auvermann; George H. Goedecke; ARMY RESEARCH LAB ADELPHI MD
|
| The objective of the ASL research effort in acoustic propagation is to provide the Army with a multi-stream model for investigating acoustic detection systems. The first step in developing this model is to account for turbulent scattering. Five elements are necessary to accomplish this step: (1) model the turbulent region as a collection of vortices with a distribution of characteristic sizes/velocities; (2) characterize each vortex ... |
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| Acoustic Wavefront Distortion and Compensation |
OCT 92 |
4 pages |
| Authors:
Robert C. Waag; ROCHESTER UNIV NY DEPT OF ELECTRICAL ENGINEERING
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| Ocean propagation models were reviewed and a ray tracing model was selected for use this research. An ray tracing program, TRIMAIN, was obtained and adapted to calculated time delay differences due to sound speed variation with depth in the ocean. An imaging algorithm was also obtained and adapted to include time delay distortion and employ data covering a finite aperture with sparse sampling. Specially modified source code was documented and ... |
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| Additional Effort in Modeling of the Non-Auditory Effects of Blast |
26 AUG 92 |
32 pages |
| Authors:
James H. Stuhmiller; JAYCOR SAN DIEGO CA
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| Work summarized in this report deals with four research areas. The first is the collection, organization, and analysis of animal pathology data which forms the basis for our current understanding of blast related hazard. The second is the refinement and validation of our predictive models of blast injury for the free-field that is the basis for our theoretical understanding of the phenomena and our means to set safety standards. The ... |
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| Spectral Characteristics of Velocity and Wall Pressure in a Ducted Flow with Dual Side and One Axial Inlets, |
23 JUL 1992 |
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| Authors:
T. -M. Liou; Y. -Y. Wu; NATIONAL TSING HUA UNIV HSINCHU (TAIWAN)
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| The velocity and wall pressure spectral characteristics of the impingement of multiple inlet jets is a ducted flow was investigated experimentally using LDV and microphone, respectively. The baseline momentum ratio of the axial- to side-inlet jet (MR) was chosen to be 0.27. In this case, a resonant feedback frequency of 365 Hz, which prevailed in the entire combustor, and the second and the third harmonics, which appeared near the impingement ... |
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| Dynamic Analysis of Quartz Glass Excited Acoustically |
JUN 1992 |
16 pages |
| Authors:
Jatin C. Parekh; Warren C. Gibson; CSA ENGINEERING INC PALO ALTO CA
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| This report describes the work performed to predict dynamic response and stress limits for quartz tubes for the NASP prototype facility. The specific objective was to evaluate the responses of several flat plate, curved plate, and tube configurations when subjected to a given level of overall sound pressure level. The RMS stress values were obtained at several locations and the maximum value for each case is reported ... |
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| Acoustic Radiation Due to Wave-Breaking |
JUN 92 |
29 pages |
| Authors:
R. M. Kennedy; S. A. Glegg; NAVAL UNDERSEA WARFARE CENTER NEW LONDON CT NEW LONDON DETACHMENT
|
| While wave-breaking is continually occurring at the sea surface, it's transient and sporadic nature makes it difficult to measure. Experimental results are presented which show how acoustic methods can be used as a remote sensor of this fundamental process. Sea surface-generated acoustic radiation (40 to 4000 Hz) is directly related to a quantitative measure of the boundary dynamics; i.e., the Toba variable. The frequency spectrum of the radiation remains remarkably ... |
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| Modeling the Ear's Response to Intense Impulses and the Development of Improved Damage Risk Criteria |
MAY 92 |
8 pages |
| Authors:
G. R. Price; HUMAN ENGINEERING LAB ABERDEEN PROVING GROUND MD
|
| Research indicates that traditional measures fail to rate hazard from intense impulses accurately. This failure may be due to increased complexities in the ear's response at such high sound pressure levels. Therefore, to gain insight into the problem, we have been developing a mathematical model of the ear that reproduces the response of the ear from free field pressures to basilar membrane displacements and calculates hazard there (modeled as mechanical ... |
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| Prediction of Jet Mixing Noise for High Subsonic Flight Speeds, |
APR 1992 |
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| Authors:
Ulf Michel; Jan Boettcher; DEUTSCHE FORSCHUNGSANSTALT FUER LUFT- UND RAUMFAHRT E V BRUNSWICK (GERMANY F R)
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| A method for the prediction of single stream jet mixing noise in flight is presented that can be used for flight Mach numbers up to 0.9. The method is similar to the empirical SAE method. However, two important results of the theoretical scaling law of Michalke and Michel are incorporated: (1) the total noise of heated jets is separated into quadrupole and dipole noise components because they are influenced differently ... |
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| Comparison of Flyover Noise Data From Aircraft at High Subsonic Speeds with Prediction, |
APR 1992 |
|
| Authors:
J. Boettcher; U. Michel; DEUTSCHE FORSCHUNGSANSTALT FUER LUFT- UND RAUMFAHRT E V BRUNSWICK (GERMANY F R)
|
| Flyover noise measurements are evaluated for four different military jet aircraft types flying at low altitudes. Flight Mach numbers ranged from 0.5 to 0.9. The analysis shows that noise immission is caused by jet mixing and broadband shock associated noise. Based on the experimental results existing noise prediction schemes are extended toward higher subsonic flight Mach numbers. The novel prediction schemes describe the observed acoustic signatures quite accurately. This holds ... |
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| Importance of Spectrum for Rating Hazard: Theoretical Basis |
MAR 92 |
16 pages |
| Authors:
G. R. Price; HUMAN ENGINEERING LAB ABERDEEN PROVING GROUND MD
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| The theoretical basis for the use of spectrum in rating hazard is well established for sound intensities most often encountered in the workplace. The frequency-selective transmission characteristics of the conductive mechanisms of the external and middle ears, coupled with the generally broad and gently sloped spectra of noise in the workplace, promote energy transmission in the midrange so that some measure of energy there should do well at ranking hazard. ... |
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| Hazardous Exposure to Impulse Noise |
1992 |
|
| Authors:
W. D. Ward; John H. Fletcher; David M. Green; Roger P. Hamernik; Daniel Johnson; NATIONAL RESEARCH COUNCIL WASHINGTON DC COMMITTEE ON HEARING BIOACOUSTICS AND BIOMECHANICS
|
| Limits for exposure to hazardous agents are set by defining some specific acceptable effect (the response) and then determining what exposure conditions (the dose) produce that effect. In 1968, the Committee on Hearing, Bioacoustics, and Biomechanics (CHABA) proposed a limit for exposure to impulse noise (gunfire) in which the response was a specific amount of temporary threshold shift (TTS) and dose was specified in terms ... |
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| Fundamental Noise Limits in Miniature Acoustic and Vibration Sensors |
31 DEC 91 |
100 pages |
| Authors:
Thomas B. Gabrielson; NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA MISSION AVIONICS TECHNOLOGY DEPT
|
| Conventional noise analysis for acoustic and vibration sensors has focused either on the ambient noise floor imposed by the environment or the electrical noise floor imposed by the preamplifier. Microminiature sensors are, however, particularly sensitive to thermal (molecular) agitation because of their small moving parts. This mechanical-thermal noise can easily dominate the noise performance of these sensors. The purposes of this report are to review the fundamental noise sources in ... |
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| Construction and Testing of a Mass Simulator for the ONR-301 EHIC experiment |
11 DEC 91 |
9 pages |
| Authors:
CHICAGO UNIV IL LAB FOR ASTROPHYSICS AND SPACE RESEARCH
|
| An Energetic Heavy Ion Composition Instrument (EHIC) was built to be flown aboard either the TIROS 'I' or 'J' spacecraft. A Mass-Volume-Electric Simulator (Mass Simulator) is required in the event that the instrument is not operational at launch or to provide ballast for whichever spacecraft the EHIC will not be installed upon at launch. This 'smart dummy' was built and tested in 1990-91 and is awaiting delivery to GE for ... |
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| Measurement and Evaluation of Blast Overpressure During F-15A Crew Station Vulnerability Assessment Test |
DEC 91 |
71 pages |
| Authors:
Harald K. Hille; ARMSTRONG LAB WRIGHT-PATTERSON AFB OH
|
| From March 1991 to May 1991 blast overpressures were measured from 21 different projectiles striking a section of the F-15 fuselage to assess potential crew hazards. The velocity of the fired projectiles ranged from 1500 ft/sec to 5000 ft/sec and the lowest overpressure which was recorded was 7 PSF or 145 dB and the highest level recorded was 1875 PSF or 194 dB sound pressure level (re 20 u Pa). ... |
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| Approximation Methods for Control of Acoustics/Structure Models with Piezoceramic Actuators |
DEC 91 |
31 pages |
| Authors:
H. T. Banks; W. Fang; R. J. Silcox; R. C. Smith; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
|
| The active control of acoustic pressure in a two dimensional cavity with a flexible boundary (a beam) is considered. Specifically, this control is implemented via piezoceramic patches on the beam which produce pure bending moments. The incorporation of the feedback control in this manner leads to a system with an unbounded input term. Approximation methods in the context of a Linear Quadratic Regulator state space formulation are discussed and numerical ... |
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| Bottom Contour Influence on Ray Tracing |
OCT 91 |
38 pages |
| Authors:
Shaari M. Unger; PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
|
| The objective of this paper is to qualitatively determine the effect changes in bottom contour will have on sound propagation using ray trace techniques. This study describes some bathymetric properties of the Nanoose Bay range. It outlines the Hamiltonian Acoustic Ray Tracing Program for the Ocean (HARPO), a ray theory based model, and discuss the relationship between ray tracing and transmission loss. HARPO ray traces are used to portray the ... |
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| Theory and Application of Scattering from an Object in an Ocean Waveguide |
OCT 91 |
244 pages |
| Authors:
Guy V. Norton; NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS
|
| A method was developed to describe acoustical scattering from an object in a waveguide by using normal mode theory to describe the incident field. Each mode is decomposed at the object into a pair of upgoing and downgoing plane waves. A transition matrix was used (developed via the extended boundary condition method of Waterman) to determine the resulting near-field scattered field. The far-field scattered field was determined by invoking Huygens' ... |
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| Inverse Tomography by Matched Field Processing. |
24 SEP 1991 |
|
| Authors:
Alexandra I. Tolstoy; Orest I. Diachok; L. N. Frazer; DEPARTMENT OF THE NAVY WASHINGTON DC
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| To determine the speed of propagation of a signal in a medium, wave amplitude is measured over time at one or more detectors disposed within the medium so as to detect and identify signals transmitted at one or more sources disposed within said region. Frequency domain matched field processing power is calculated by matching measured with perturbation normal mode model fields, and beta coefficients which determine sound speed profiles are ... |
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| Predictions and Observations of Seafloor Infrasonic Noise Generated by Sea Surface Orbital Motion |
SEP 91 |
|
| Authors:
Timothy E. Lindstrom; MASSACHUSETTS INST OF TECH CAMBRIDGE
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| A model is developed for the prediction of the seismo-acoustic noise spectrum in the microseism peak region 0.1 to 0.7 Hz. The model uses a theory developed by Cato (1991) for an infinite depth ocean in which the surface orbital motion caused by gravity waves may produce acoustic waves at twice the gravity wave frequency. Using directional wave spectra as inputs, acoustic source levels are computed and incorporated into a ... |
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| The Effect of Impulse Presentation Order on Hearing Trauma in the Chinchilla |
SEP 91 |
70 pages |
| Authors:
James H. Patterson Jr.; Dennis L. Curd; Ilia L. Gautier; Roger P. Hamernik; William A. Ahroon; ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
|
| Existing criteria for exposure to impulse noise do not provide any explicit means for evaluating exposures for which the peak SPL (Sound Pressure Level) of the impulses varies in any given exposure day. Approaches to evaluating such exposures have included the application of a 'proportional dose' method such as used with continuous noise or use of an average level. Implicit in these approaches is the assumption that the order in ... |
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| Aeroacoustics of Flight Vehicles: Theory and Practice. Volume 2. Noise Sources |
AUG 91 |
446 pages |
| Authors:
Harvey H. Hubbard; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER
|
| The field of aeroacoustics has matured dramatically in the past two decades. Researchers have gained significant theoretical and experimental understanding of the noise generated by aircraft power plants and their components. In addition, airframe noise and interior noise have been investigated extensively. The physical understanding obtained from these efforts has resulted in the development of hardware capable of reducing community noise and of meeting strict noise certification requirements. Reductions in ... |
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| Development of a Pressure Transducer Calibration System (Dynamic Pressure Response Caliber). Phase 2 |
AUG 91 |
53 pages |
| Authors:
Joseph R. Maly; David A. Kienholz; CSA ENGINEERING INC PALO ALTO CA
|
| Current dynamic pressure calibrators are restricted in ultimate peak pressure, bandwidth, and accuracy; in fact, static calibrations are commonly performed for dynamic transducers. A dynamic transducer calibration system has been developed for the bandwidth of 2 to 2,500 Hz. Controlled pressure can be provided, in sine or random format, for a standard transducer and a test transducer. For the frequency bands of 2 to 150 Hz and 1,600 to 2,400 ... |
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| Practical Wind Speed and Rain Rate Prediction from Underwater Noise |
AUG 91 |
32 pages |
| Authors:
M. H. Pickett; R. L. Pickett; NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS
|
| Equations for estimating wind speed and rain rate from underwater noise are derived in this paper. Data from both this study and other published studies were used. Data for this study were collected during Oct and Nov 1988 off south Florida in 50 m of water. Noise levels at 12 frequencies from 0.5 to 30 kHz were recorded, edited and grouped. Regression was used to derive site- specific prediction equations ... |
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| The Evaluation of a Propeller Unsteady Force Computer Program to Predict Propeller Induced Unsteady Hull Pressures |
JUL 91 |
66 pages |
| Authors:
W. G. Berberich; R. C. Marboe; PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
|
| A potential flow computer program is used to predict the unsteady pressure field on a hullform caused by a rotating propeller. It was chosen over two other approaches and three programs. The program, PUF-3A, uses lifting surface theory and contains variables that are run in different combinations to ascertain their effects. The results are plots of sound pressure level, SPL, versus distance across the hullform and are compared to water ... |
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| Response of Propellant Combustion to Unsteady Turbulent Flows |
JUN 91 |
66 pages |
| Authors:
Robert A. Beddini; Ted A. Roberts; ILLINOIS UNIV AT URBANA
|
| Turbularization of an acoustic boundary-layer (Stokes layer) on impermeable and permeable surfaces is analytically considered. The theoretical approach utilizes a second-order closure model of turbulence. For simple acoustic boundary-layers on impermeable surfaces, both the approximate solution and the numerical results for the critical acoustic Mach number required for turbulent transition are qualitatively confirmed by experiment. The calculations for acoustic boundary-layers with transpiration (injection) indicate a substantial reduction of the acoustic ... |
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| Minutes: Accredited Standards Committee on Acoustics, S1 U.S. Tag for ISO/TC43 Acoustics and IEC/TC29 Electroacoustics |
02 MAY 91 |
112 pages |
| Authors:
ACOUSTICAL SOCIETY OF AMERICA NEW YORK
|
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| U.S. TAG for ISO/TC43 Acoustics and IEC/TC29 Electroacoustics (Minutes for the Accredited Standards Committee on Acoustics, S1) |
02 MAY 91 |
110 pages |
| Authors:
ACOUSTICAL SOCIETY OF AMERICA NEW YORK
|
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| Acoustic Noise Recording and DRT/Dam Source Tape Generation |
MAR 91 |
|
| Authors:
Charles Teacher; John D. Tardelli; Paul D. Gatewood; ARCON CORP WALTHAM MA
|
| This study was aimed at the determination of procedures and techniques by which binaural sound fields created by Air Force vehicles could be accurately recorded in insitu and reproduced in a Rome Laboratory/RL sound chamber in order to enable accurate simulations for the generation of intelligibility and quality source material for the testing of narrowband digital voice communication systems. The sound fields were digitally recorded through a set of spectrally ... |
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| Investigation of Edge Effects in Thermoacoustic Couple Measurements |
DEC 1990 |
48 pages |
| Authors:
Wei-Hsin Liu; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Previous measurements of thermoacoustic heat transport across stacks of short plates, called thermoacoustic couples or TACs, revealed serious discrepancies between theory and experiment. The discrepancies are worst at higher drive ratios (the ratio of the peak acoustic pressure amplitude at a pressure antinode to the mean pressure of the gas), where prominent irregularities in the data series appear. In the previous work, the measurements were made with thermopiles having junctions ... |
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| Comparison of Sound Pressure in a Wedge-Shaped Ocean as Predicted by an Image Method and a PE Model |
DEC 90 |
45 pages |
| Authors:
Jong R. Kim; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| We compare and contrast results of three different models of acoustic propagation in an ocean with a sloping bottom, predicting the pressure field in a wedge-shaped ocean with a pressure release surface and an acoustically fast bottom. On image and two PE (Parabolic Equation) models were selected. The computer model for the image method was written in Basic for use on a PC and in Fortran for use on the ... |
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| Electrolysis Bubble Noise in Small-Scale Tests of a Seawater MHD thruster |
SEP 90 |
50 pages |
| Authors:
Kenneth E. Tempelmeyer; DAVID TAYLOR RESEARCH CENTER BETHESDA MD
|
| Sound pressure levels were measured during the electro lysis process of seawater in a magnetohydrodynamic-type channel, but without an applied magnetic field. The test configuration was a small-scale version of a seawater magnetohydrodynamic (MHD) thruster and the test conditions were similar to those which might occur in an undersea MHD-powered vessel. The electrolysis of sea water at current densities up to 0.3 A/cm2 produced broad-band noise at frequencies above 2 ... |
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| Measurement of the Complex Reflectivity of Submerged Thin Plates at Oblique Incidence Angles Using the Two-Sensor Intensity Technique |
AUG 90 |
122 pages |
| Authors:
D. W. DeVilbiss; A. D. Stuart; PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
|
| This study has involved the adaptation of the two-sensor acoustic intensity measurement method to an underwater environment. The intensity technique involves measuring the acoustic pressure at two closely spaced points. The average of the pressures approximates the pressure at the midpoint of the two sensors while the difference between the pressures and the application of the Euler's equation leads to an approximation for the acoustic particle velocity at the midpoint ... |
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| Effects of Turbulence on Stationary and Nonstationary Processes in C- Systems |
23 JUL 90 |
77 pages |
| Authors:
Robert A. Beddini; Ted A. Roberts; ILLINOIS UNIV AT URBANA DEPT OF AERONAUTICAL AND ASTRONAUTICAL ENGINEERING
|
| Turbularization of an acoustic boundary-layer (Strokes layer) on impermeable and permeable surfaces is analytically considered. The theoretical approach utilizes a second-order closure model of turbulence. An approximate, closed form solution and a more comprehensive finite difference solution of the time dependent, parabolic, one dimensional governing equations are obtained. For simple acoustic boundary layers on impermeable surfaces, the approximate solution and the numerical results for the critical acoustic Mach number required ... |
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| A Low-Frequency, Tow-Powered Sound Source |
JUN 90 |
23 pages |
| Authors:
J. E. Blue; A. L. Van Buren; NAVAL RESEARCH LAB ORLANDO FL UNDERWATER SOUND REFERENCE DETACHMENT
|
| This paper discusses resonant cavities and their potential sound pressure output when they are modulated hydrodynamically. Rough calculations show that in the frequency range of 10 to 100 Hz source levels in excess of 200 dB re 1 micro Pa should be achievable. Experimental data from three suboptimum devices showed source levels of 182 dB at 16.6 and 50 Hz and 168 dB at 34.5 Hz. It is expected that ... |
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| Effect of Surface Ship Internal Fluid Containers on External Acoustic Intensity Measurements |
MAY 90 |
|
| Authors:
Amy R. Smith; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
| The nearfield acoustic intensity resulting from vibration transmitted from a main machinery foundation through supporting structure and fluid containing tanks into the hull structure, and then into the surrounding fluid has been studied for a scale model of a frigate ship. The scale model is 1:10 and the scaled frequency range is 640 Hz to 15 kHz. Acoustic pressure is measured on adjacent cylindrical contours close to the surface of ... |
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| Radial Instabilities of a Pulsating Air Bubble in Water |
30 JAN 90 |
296 pages |
| Authors:
Steven D. Horsburgh; Lawrence A. Crum; NATIONAL CENTER FOR PHYSICAL ACOUSTICS UNIVERSITY MS
|
| Recently, several theoretical studies have been originated concerning the spherical stability of a pulsating air bubble in water. In this study, a light scattering technique was utilized to record in real-time the motion of the bubble surface. The main objective was to experimentally determine the shape oscillation threshold of an acoustically driven air bubble in water. These thresholds were defined as the minimum pressure necessary to drive a bubble, at ... |
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| Field Calibration of Two Types of Microphones in Hyperbaric Air |
16 JAN 90 |
17 pages |
| Authors:
Paul F. Smith; Susan Carpenter; John Green; NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
|
| The response of two microphones, one a condenser microphone and the other a diaphragm-activated piezoelectric ceramic microphone, were measured in compressed air at pressures as great as 810 kilopascals (8 atmospheres). The response of each microphone was compared to that of a hydrophone operated in air as a microphone. The results show that the two types of microphone respond similarly to high ambient pressure. Both types are less sensitive to ... |
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| The Validation and Application of a Rotor Acoustic Prediction Computer Program |
90 |
16 pages |
| Authors:
Judith M. Gallman; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCH CENTER
|
| An essential prerequisite to reducing the acoustic detectability of military rotorcraft is a better understanding of main rotor noise which is the major contributor to the overall noise. A simple, yet accurate, Rotor Acoustic Prediction Program (RAPP) has been developed to advance the understanding of main rotor noise. This prediction program uses the Fforwcs Williams and Hawkings (FW-H) equation. The particular form of the FW-H equation used is well suited ... |
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| Numerical Pulse Propagation Studies Using Two Classical Ocean Waveguide Models |
DEC 89 |
90 pages |
| Authors:
Marinos P. Markopoulos; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Numerical pulse propagation studies using two classical ocean waveguide models are performed. The first model is a pressure-release surface with a rigid bottom. The second model is a pressure-release surface with a fluid bottom. The analysis of the two models is based on normal mode theory assuming a constant speed of sound in the ocean. The magnitude and phase of the complex acoustic pressure field as a function of frequency ... |
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| Apparatus to Determine the Complex Mass of a Viscous Fluid Contained in a Rigid Porous Solid from Acoustic Pressure Measurements |
DEC 89 |
52 pages |
| Authors:
Robert A. Mirick; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Two experimental techniques to determine the frequency-dependent complex mass of a viscous fluid contained in a rigid porous solid are investigated. In one technique the moving mass of the fluid is by its effect on the measured input electrical impedance of a moving coil transducer. In the second technique the moving mass is extracted from the measured acoustic pressure required for the fluid to oscillate with a known amplitude through ... |
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| Echolocation Signals of Odontocetes in Open Waters |
DEC 89 |
1 pages |
| Authors:
W. W. Au; NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA
|
| The characteristics of echolocation signals used by the Atlantic bottlenose dolphin. (Tursiops truncatus) and by the beluga or white whale (Delphinapterus leucas) in target detection and discrimination experiments in open waters will be discussed. Echolocation signals measured in open waters have been found to have considerably different properties than those measured in tanks. The primary reason for the differences in echolocation signals may be attributed to the use of very-low-intensity ... |
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| Acoustic Intensity Probe. |
13 NOV 1989 |
|
| Authors:
Kam W. Ng; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An acoustic intensity probe was developed to measure waterborne sound intensity levels using a two-hydrophone technique. The technique utilizes the cross-spectral density of signals from multiple closely spaced hydrophones. Planar (2-dimensional) and 3-dimensional arrays of hydrophones with symmetric and asymmetric configurations were developed to measure the acoustic intensity levels. This acoustic intensity probe combined with the two-hydrophone technique provides specific information revealing the acoustic energy distribution and propagation of noise ... |
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| The Acoustic Startle Response and Disruption of Aiming. 1. Effect of Stimulus Repetition, Intensity, and Intensity Changes |
NOV 89 |
17 pages |
| Authors:
John A. Foss; James R. Ison; James P. Torre Jr.; Samuel Wansack; HUMAN ENGINEERING LAB ABERDEEN PROVING GROUND MD
|
| Three experiments examined the disruption of perceptual motor performance by intense noise bursts. Subjects aimed a rifle at a fixed target for 15-s periods separated by 15 s of rest. This cycle was repeated 30 times in each of two series separated by a 15-min rest, each series containing five noise bursts. The noise bursts disrupted aiming for 1-2 s, an effect that increased with sound pressure level for 110, ... |
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| Effects of Military Training Route Noise on Human Annoyance |
OCT 89 |
72 pages |
| Authors:
C. S. Harris; HARRY G ARMSTRONG AEROSPACE MEDICAL RESEARCH LAB WRIGHT- PATTERSON AFB OH
|
| Forty-nine subjects were tested in four experiments. Each subject experienced all conditions within his particular study. All experiments were designed to compare equal energy low onset rate flyovers with high onset rate flyovers. A measure of annoyance taken after each simulated aircraft flyover was the more sensitive measure of low versus high onset rate. The results indicate that onset rate contributes annoyance that adds to the annoyance produced by the ... |
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| Preliminary Sound-Abatement Tests Using Shock-Attenuating Concrete (SACON) and Other Materials, Big Black Test Facility |
AUG 89 |
25 pages |
| Authors:
William L. Huff; Gary L. Carre; Terry R. Stanton; Joe G. Tom; Robert H. Denson; ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS STRUCTURES LAB
|
| Two structural concepts, a tunnel and an igloo, were constructed at the US Army Engineer Waterways Experiment Station using a shock-attenuating concrete (SACON) to determine the possible sound-abatement properties. Both structures and the SACON displayed sound abatement properties, as registered on hand-held sound level meters, when an M-16-Al rifle was fired in certain positions in and near the two structures. A noticeable reduction in sound was obtained by the use ... |
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Reports by Keyword(s)
SOUND PRESSURE
