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Author: National Aeronautics and Space Adm Nasa
Publisher:
ISBN: 9781729022221
Category :
Languages : en
Pages : 34
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Book Description
The results of a scale model propagation experiment to investigate grazing propagation above a finite impedance boundary are reported. In the experiment, a 20 x 25 ft ground plane was installed in an anechoic chamber. Propagation tests were performed over the plywood surface of the ground plane and with the ground plane covered with felt, styrofoam, and fiberboard. Tests were performed with discrete tones in the frequency range of 10 to 15 kHz. The acoustic source and microphones varied in height above the test surface from flush to 6 in. Microphones were located in a linear array up to 18 ft from the source. A preliminary experiment using the same ground plane, but only testing the plywood and felt surfaces was performed. The results of this first experiment were encouraging, but data variability and repeatability were poor, particularly, for the felt surface, making comparisons with theoretical predictions difficult. In the main experiment the sound source, microphones, microphone positioning, data acquisition, quality of the anechoic chamber, and environmental control of the anechoic chamber were improved. High-quality, repeatable acoustic data were measured in the main experiment for all four test surfaces. Comparisons with predictions are good, but limited by uncertainties of the impedance values of the test surfaces. Willshire, William L., Jr. Langley Research Center RTOP 505-63-91-02...
Author: National Aeronautics and Space Adm Nasa
Publisher:
ISBN: 9781729022221
Category :
Languages : en
Pages : 34
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Book Description
The results of a scale model propagation experiment to investigate grazing propagation above a finite impedance boundary are reported. In the experiment, a 20 x 25 ft ground plane was installed in an anechoic chamber. Propagation tests were performed over the plywood surface of the ground plane and with the ground plane covered with felt, styrofoam, and fiberboard. Tests were performed with discrete tones in the frequency range of 10 to 15 kHz. The acoustic source and microphones varied in height above the test surface from flush to 6 in. Microphones were located in a linear array up to 18 ft from the source. A preliminary experiment using the same ground plane, but only testing the plywood and felt surfaces was performed. The results of this first experiment were encouraging, but data variability and repeatability were poor, particularly, for the felt surface, making comparisons with theoretical predictions difficult. In the main experiment the sound source, microphones, microphone positioning, data acquisition, quality of the anechoic chamber, and environmental control of the anechoic chamber were improved. High-quality, repeatable acoustic data were measured in the main experiment for all four test surfaces. Comparisons with predictions are good, but limited by uncertainties of the impedance values of the test surfaces. Willshire, William L., Jr. Langley Research Center RTOP 505-63-91-02...
Author: Selma Kurra
Publisher:
ISBN:
Category :
Languages : tr
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 36
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Book Description
Author: Tony L. Parrott
Publisher:
ISBN:
Category : Sound-waves
Languages : en
Pages : 58
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Book Description
Author: Tony L. Parrott
Publisher:
ISBN:
Category :
Languages : en
Pages : 60
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Book Description
Author: A. N. Barkhatov
Publisher: Springer
ISBN: 9781468415834
Category : Technology & Engineering
Languages : en
Pages : 91
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Book Description
The book is concerned with the application of modeling techniques and procedures to the investigation of sound propagation in the sea. The modeling method affords a means for studying the laws governing the sound fields in the sea and in other, similar media under controlled laboratory conditions and can be used in underwater acoustics as a coroHary to field experiments. The method has a number of advantages, principal of which are the relative simplicity and low cost of model tests by com parison with fuH-scale tests under oceanic conditions, the high accuracy of acoustical mea surements, excellent reproducibility of the measurement results, and the capability of rapidly varying the experimental conditions, which, unlike the conditions of field experiments, are under complete control. For the modeling of sound propagation in the sea the latter is treated, depending on the problem to be solved, either as a volume-homogeneous medium or as a medium possessing regular and randomly-distributed inhomogeneities. We direct our primary attention in the book to the modeling of layered-inhomogeneous media, but we also discuss separate problems bearing on the study of sound propagation in the sea. It is demonstrated in examples how modeling is employed to investigate the sound field in the ocean for certain typical vertical distributions of the velocity of sound in the ocean.
Author: Nasa Technical Reports Server (Ntrs)
Publisher: BiblioGov
ISBN: 9781289164836
Category :
Languages : en
Pages : 66
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Book Description
The NASA Technical Reports Server (NTRS) houses half a million publications that are a valuable means of information to researchers, teachers, students, and the general public. These documents are all aerospace related with much scientific and technical information created or funded by NASA. Some types of documents include conference papers, research reports, meeting papers, journal articles and more. This is one of those documents.
Author: Aleksandr Nikolaevich Barkhatov
Publisher: Springer
ISBN:
Category : Science
Languages : en
Pages : 116
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Book Description
The book is concerned with the application of modeling techniques and procedures to the investigation of sound propagation in the sea. The modeling method affords a means for studying the laws governing the sound fields in the sea and in other, similar media under controlled laboratory conditions and can be used in underwater acoustics as a coroHary to field experiments. The method has a number of advantages, principal of which are the relative simplicity and low cost of model tests by com parison with fuH-scale tests under oceanic conditions, the high accuracy of acoustical mea surements, excellent reproducibility of the measurement results, and the capability of rapidly varying the experimental conditions, which, unlike the conditions of field experiments, are under complete control. For the modeling of sound propagation in the sea the latter is treated, depending on the problem to be solved, either as a volume-homogeneous medium or as a medium possessing regular and randomly-distributed inhomogeneities. We direct our primary attention in the book to the modeling of layered-inhomogeneous media, but we also discuss separate problems bearing on the study of sound propagation in the sea. It is demonstrated in examples how modeling is employed to investigate the sound field in the ocean for certain typical vertical distributions of the velocity of sound in the ocean.
Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781723883132
Category : Science
Languages : en
Pages : 64
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Book Description
The Launch Systems Testbed (LST) represents the evolution of vibroacoustics research and development work performed at NASA John F. Kennedy Space Center (KSC) over the last 15 years. The LST is located at the Launch Equipment Test Facility (LETF) in the KSC industrial complex. The LETF is operated by Sierra Lobo, Inc., as a member of University-Affiliated Technology Development Contract (USTDC) to KSC Spaceport and Engineering and Technology Directorate (YA), with ASRC Aerospace Corporation as a the prime contractor. Trajectory Simulation Mechanism (TSM) is a major component of the LST, developed specifically to simulate nonstationary acoustic loads on launch pad structures, vehicles, and payloads. TSM enhances the capabilities within LST for simulating launch environments of future vehicles. The scaled launch environments will be used to predict the full-scale launch environment via an appropriate scaling procedure. Air Force Research Laboratory (AFRL) has tasked NASA KSC to perform a basic technology test program in support of developing a low-cost clean pad (incorporating passive mitigation techniques) for future launch vehicles. The overall goal of the program is to develop innovative launch exhaust management systems, which effectively reduce launch acoustic environment with innovative duct designs, while eliminating traditional sound suppression water systems. Passive techniques, such as nontraditional duct geometries, resonators, and diffusers, etc., will be investigated. The overall goals are to advance innovative concepts for a clean pad while developing ideas to reduce transmitted sound via investigation and modeling of jet exhaust acoustic and flow field characteristics. The series of tests outlined in this report represent baseline tests and are geared towards defining the acoustic load environment on the TSM pad for open and closed duct configurations. This report summarizes the cold jet acoustic testing for Mach 2.5 supersonic nitrogen jet issuing from
Author: Martin Almgren
Publisher:
ISBN:
Category :
Languages : en
Pages :
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