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  • Acoustics
  • 2015-2019
  • 1990-1994
  • 1960-1964  (4)
  • 1945-1949
  • 1960  (4)
  • 1
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    The long time response of a layered elastic medium to explosive sound (1960)
    In:  J. Geophys. Res., Oslo, Wiley, vol. 65, no. 1-2, pp. 1577-1613, pp. TC4013, (ISSN: 1340-4202)
    Details
    Publication Date: 1960
    Keywords: Seismology ; Layers ; Acoustics ; JGR
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Transonic Performance Characteristics of Several Jet Noise Suppressors (1960)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: An investigation of the transonic performance characteristics of several noise-suppressor configurations has been conducted in the Langley 16-foot transonic tunnel. The models were tested statically and over a Mach number range from 0.70 to 1.05 at an angle of attack of 0 deg. The primary jet total-pressure ratio was varied from 1.0 (jet off) to about 4.5. The effect of secondary air flow on the performance of two of the configurations was investigated. A hydrogen peroxide turbojet-engine simulator was used to supply the hot-jet exhaust. An 8-lobe afterbody with centerbody, short shroud, and secondary air had the highest thrust-minus-drag coefficients of the six noise-suppressor configurations tested. The 12-tube and 12-lobe afterbodies had the lowest internal losses. The presence of an ejector shroud partially shields the external pressure distribution of the 8-lobe after-body from the influence of the primary jet. A ring-airfoil shroud increased the static thrust of the annular nozzle but generally decreased the thrust minus drag at transonic Mach numbers.
    Keywords: Acoustics
    Type: NASA-TN-D-388 , L-850
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Diffusion of Sound Waves in a Turbulent Atmosphere (1960)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: The directional and frequency diffusion of a plane monochromatic 2 sound wave in statistically homogeneous, isotropic, and stationary turbulence is analyzed theoretically. The treatment is based on the diffusion equation for the energy density of sound waves, using the scattering cross section derived by Kraichnan for the type of turbulence assumed here. A form for the frequency-wave number spectrum of the turbulence is adopted which contains the pertinent parameters of the flow and is adapted to ease of calculation. A new approach to the evaluation of the characteristic period of the flow is suggested. This spectrum is then related to the scattering cross section. Finally, a diffusion equation is derived as a small-angle scattering approximation to the rigorous transport equation. The rate of spread of the incident wave in frequency and direction is calculated, as well as the power spectrum and autocorrelation for the wave.
    Keywords: Acoustics
    Type: NASA-TN-D-456 , W-127
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Some Measurements of Noise Transmission and Stress Response of a 0.020-Inch Duralumin Panel in the Presence of Air Flow (1960)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Noise transmission measurements were made for a 0.020-inch panel with and without air flow on its surface. Tests were conducted with both an absorbent and reverberant chamber behind the panel. Panel stresses for some of these tests were also determined. Noise spectra obtained inside the absorbent chamber with flow attached and flow not attached to the panel appeared to contain several peaks corresponding in frequency to panel vibration modes. These peaks were notably absent when the chamber was reverberant. The noise reduction through the test panel measured with the aid of an absorbent chamber for the flow-not-attached case is in general agreement with values predicted by the theoretical weight law, which assumes negligible panel stiffness. Corresponding data for the flow-attached case do not follow the weight law but rather indicate less noise reduction at the high frequencies. The main stress responses of the panel without air flow occurred at its fundamental vibration mode. In the presence of air flow the main response occurs in a vibration mode having a node line perpendicular to the direction of air flow.
    Keywords: Acoustics
    Type: NASA-TN-D-459 , L-609
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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