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Transonic drag of several jet-noise suppressors

Description: Investigation of the aerodynamic drag of several jet noise suppressors over a range of Mach numbers and several nozzle pressure ratios. The least drag was caused by lobe-type suppressors. The eight-lobe nozzle with ejector caused the greatest amount of drag.
Date: April 1958
Creator: North, Warren J.
Partner: UNT Libraries Government Documents Department

Ground reflection of jet noise

Description: Report presenting the effect of a reflecting plane on the propagation of jet noise investigated theoretically and experimentally. The primary focus of the study is to determine the free-field spectrum of subsonic-jet noise from measurements made in the presence of a ground plane.
Date: April 1958
Creator: Howes, Walton L.
Partner: UNT Libraries Government Documents Department

Investigation of far noise field of jets 2: comparison of air jets and jet engines

Description: Report presenting a comparison of the noise generation of air jets and turbojet engines under similar free-flight conditions. Results regarding a comparison of the sound power, afterburner data, spectrum measurements, noise data for engine thrust, and frequency distribution for the two engines are provided.
Date: January 1956
Creator: Coles, Willard D. & Callaghan, Edmund E.
Partner: UNT Libraries Government Documents Department

The Effect of White Noise on a Visual Discrimination Task

Description: Previous studies have demonstrated that in some instances certain types of auditory stimulation have facilitated a subject's ability at a visual task while in other instances, the subject's ability has been inhibited. The primary objective of this experiment was to investigate the effect of auditory stimulation upon a subject's performance on a visual discrimination task.
Date: January 1969
Creator: Smith, James Larry
Partner: UNT Libraries

Spontaneous Brain Activity as a Source of Ideal 1/f Noise

Description: In this article, the authors study the electroencephalogram (EEG) of 30 closed-eye subjects with a technique of analysis recently proposed to detect punctual events signaling rapid transitions between different metastable states.
Date: December 18, 2009
Creator: Allegrini, Paolo; Menicucci, Danilo; Bedini, Remo; Fronzoni, Leone; Gemignani, Angelo; Grigolini, Paolo et al.
Partner: UNT College of Arts and Sciences

Investigation of noise field and velocity profiles of an afterburning engine

Description: Report presenting sound pressure levels, frequency spectrum, and jet velocity profiles for an engine-afterburner combination at various values of afterburner fuel-air ratio. Lower sound pressure levels were obtained from a current fighter aircraft with a different afterburner configuration. Results regarding the jet temperature, jet Mach number and velocity, and sound measurements are provided.
Date: September 24, 1954
Creator: North, Warren J.; Callaghan, Edmund E. & Lanzo, Chester D.
Partner: UNT Libraries Government Documents Department

Acoustic, thrust, and drag characteristics of several full-scale noise suppressors for turbojet engines

Description: From Introduction: " Considerable analytical and experimental research has been done to find means of reducing the noise levels of the turbojet transports. Noise levels can be decreased by engine redesign to reduce the jet-exit velocity (ref. 1), proper flight-climb techniques (ref. 2), and the use of noise-suppression exhaust nozzles (refs. 3 to 5). The present report is concerned with the last method."
Date: April 1958
Creator: Ciepluch, Carl C.; North, Warren J.; Coles, Willard D. & Antl, Robert J.
Partner: UNT Libraries Government Documents Department

Screen-type noise reduction devices for ground running of turbojet engines

Description: Report presenting testing of the use of screens placed across the jet as a means of suppressing jet noise during ground running, which was somewhat offset by increased noise levels ahead of the engine. Air-jet tests showed negligible reduction in sound generation with additional screens. The large reductions obtained by using screens show that noise generated inside the engine by the turbine or combustion contribute only a minor part of the total noise.
Date: July 1957
Creator: Coles, Willard D. & North, Warren J.
Partner: UNT Libraries Government Documents Department

Preliminary flight survey of aerodynamic noise on an airplane wing

Description: Report presenting a brief series of airplane-wing aerodynamic-noise and boundary-layer-profile measurements made in flight as part of an extended investigation of boundary-layer noise. Results regarding the boundary layer data and ratio of root-mean-square sound pressure to the dynamic pressure are provided.
Date: March 2, 1956
Creator: Mull, Harold R. & Algranti, Joseph S.
Partner: UNT Libraries Government Documents Department

An investigation of some phenomena relating to aural detection of airplanes

Description: Report presenting an investigation to determine the effect of modifications made in the propulsion system of a single-engine airplane to substantially reduce its external noise, and, thereby, to evaluate the significance of the external noise level of an airplane with regard to the problem of its detection by ground observers.
Date: September 1958
Creator: Hubbard, Harvey H. & Maglieri, Domenic J.
Partner: UNT Libraries Government Documents Department

Sound from a two-blade propeller at supersonic tip speeds

Description: Report presents the results of sound measurements at static conditions made for a two-blade 47-inch-diameter propeller in the tip Mach number range 0.75 to 1.30. For comparison, spectrums have been obtained at both subsonic and supersonic tip speeds. In addition, the measured data are compared with calculations by the theory of Gutin which has previously been found adequate for predicting the sound at subsonic tip speeds. Curves are presented from which the maximum over-all noise levels in free space may be estimated if the power, tip Mach number, and distance are known.
Date: March 29, 1951
Creator: Hubbard, Harvey H. & Lassiter, Leslie W.
Partner: UNT Libraries Government Documents Department

Some aspects of the helicopter noise problem

Description: "Some aspects of the helicopter noise problem are briefly discussed. These discussions deal with the nature of the problem, some tentative criteria for use in evaluating it, and the physical characteristics of noise from helicopters. Overall noise data are presented for a reciprocating-engine helicopter along with discussions of the characteristics of noise from its various components such as the engine, gearing, and rotors. Some consideration is also given to the noise from tip jet rotor systems" (p. 1).
Date: August 1954
Creator: Hubbard, Harvey H. & Lassiter, Leslie W.
Partner: UNT Libraries Government Documents Department

Noise survey of a 10-foot four-blade turbine-driven propeller under static conditions

Description: Report presenting an analysis of overall sound-level measurements and frequency analyses of tape recordings of the noise emitted from a 10-foot-diameter, four-blade propeller mounted on a turbine-powered vehicle under static conditions at stations equally spaced on a 75-foot-radius circle. Results regarding the distribution of overall sound-pressure levels and distribution of sound-pressure levels for the first four propeller harmonics are provided.
Date: July 1955
Creator: Kurbjun, Max C.
Partner: UNT Libraries Government Documents Department

Intensity, scale, and spectra of turbulence in mixing region of free subsonic jet

Description: Report presents the results of the measurements of intensity of turbulence, the longitudinal and lateral correlation coefficients, and the spectra of turbulence in a 3.5-inch-diameter free jet measured with hot-wire anemometers at exit Mach numbers from 0.2 to 0.7 and Reynolds numbers from 192,000 to 725,000.
Date: April 24, 1956
Creator: Laurence, James C.
Partner: UNT Libraries Government Documents Department

The Effect of Noise on Pulse Height Resolution

Description: Report wherein "[a] statistical study of base line fluctuations is used to relate noise measurements with the resolution spread of a pulse height analysis system. The resolution is inversely proportional to the signal-to-noise ratio. The proportionality constant is derived on the basis of a normal amplitude distribution for noise. A review of noise measuring techniques is given and adapted for use with electronic voltmeters. The form factors required to interpret meter readings in terms of the RMS value of noise are described" (p. 1).
Date: January 1962
Creator: Meth, Irving M. & Graveson, Robert T.
Partner: UNT Libraries Government Documents Department

Noise Pollution from Expressways

Description: This paper provides an economic analysis of three noise abatement strategies designed to interrupt the path of noise between highways and residential areas, and makes some abatement policy suggestions.
Date: June 1976
Creator: Vaughan, Roger J. & Huckins, Larry
Partner: UNT Libraries Government Documents Department