Showing papers on "Aircraft noise published in 1968"

Structural-acoustic response, noise transmission losses and interior noise levels of an aircraft fuselage excited by random pressure fields

Abstract: : A theoretical and empirical study of the structural-acoustic response and sound transmission properties of fuselage structures is described. The external fluctuating pressure environments discussed are boundary layer turbulence, jet noise and reverberant acoustic fields. In order to investigate the complete behavior of the fuselage, equivalent structural models are analyzed whose combined characteristics represent the complex fuselage structure throughout the entire frequency response range of interest. The structure and interior sound field are treated throughout as a coupled dynamic system whose response is describable in terms of the system's normal modes. Prediction methods are developed for structural responses, noise reduction and internal acoustic fields of untreated and acoustically treated fuselage structures. The results of this study have been programmed for computer solution, thus allowing the significant parameters affecting sound transmission to be determined. In addition to the computer programs, empirical design charts are presented for carrying out pre-design estimates of the external fluctuating loads due to boundary layer turbulence and jet noise and overall noise reduction of typical acoustic treatments.

Aircraft noise evaluation

Abstract: : The Federal Aviation Administration, in response to Public Law 90- 411, has begun the rule making process leading to the certification of aircraft for noise. The basic element in the regulation criteria is the noise evaluation measure designated as effective perceived noise level, EPNL, which is a single number evaluator of the subjective effects of aircraft noise on human beings. Simply stated, EPNL consists of instantaneous perceived noise level corrected for tones and duration. The history of the development of EPNL is presented and a critical evaluation of its validity is made. The computational procedures are described in detail including both integration and approximate methods for calculating duration corrections. Examples are given in the appendices.

Psychological Experiments on Sonic Booms Conducter at Edwards Air Force Base

Abstract: : A series of tests were conducted in June 1966 and October 1966 to January 1967 in which human subjects (located indoors and outdoors), and special test structures were exposed to booms from F-104, F-106, B-58, SR-71, and XB-70 supersonic aircraft, and the noise from KC-136 and WC-135B subsonic aircraft. Physical measurements were made of the sonic boom signatures, subsonic aircraft noise, and the response of structures to the booms and noise. Psychological measurements were made of the subjective acceptability to several hundred subjects of the booms and subsonic aircraft noise. Details of the test plan and procedures, and the results of the data analyzed are presented.

Comparisons between subjective ratings of aircraft noise and various objective measures.

Abstract: : Various established and proposed objective methods of measuring aircraft noise were evaluated with respect to their ability to predict subjective ratings of the acceptability of noise produced by present-day commercial aircraft. Recorded flyovers of several types of aircraft during takeoff and landing operations were selected, and other flyovers were electronically simulated. Paired-comparison listening tests were used to determine the level at which each flyover was considered to be as acceptable as a reference sound. Objective measures corresponding to this level were computed for each flyover. The relative accuracy with which the objective measures predicted the subjective ratings was expressed in terms of the variance in the computed values of each objective measure. The smallest variance was associated with a measure that takes into account the spectral properties of a given flyover for its entire duration and also the presence of pure tones or other narrow-band energy concentrations. (Author)

A realistic assessment of the vertiport/ community noise problem.

Abstract: An increase of background noise has accompanied the steady growth of industrial society. Rapid growth of air travel has focused special attention on aircraft noise, and need for abatement. Anticipated growth of short-haul air transport will bring vertiports into established commercial areas and low-altitude flyovers to populated areas. Noise intrusion may be assessed in perceived noise (PNdb) for residential communities, but a more realistic yardstick for commercial/industrial sections might be speech interference level (SIL). Achievement of the ideal goal—no intrusion of noise above ambient levels—requires reduction of powerplant noise but may be limited by aerodynamic noise from the vehicle itself. Consideration of powerplant noise in terms of "disk loading," progressing from jets at the high end down through fans, propellers, and rotors, leads to selection of rotors and propellers for shorthaul propulsion. Further noise reduction below current state-of-the-art levels will require intensive long-range development programs. Parallel to concentrated effort by industry to provide aircraft acoustically acceptable to the community, the community should plan for these aircraft by judicious selection of vertiport sites and utilization of zoning and building-code functions for development of surrounding neighborhoods.

Results of recent NASA research pertinent to aircraft noise and sonic-boom alleviation.

Abstract: NASA research results pertinent to airport- community noise problems and sonic boom alleviation

Community noise--the industrial aspect.

Abstract: Often community noise control regulations are hastily developed and contain unrealistic features. Transportation, home, and other community noise sources are neglected with resulting emphasis on the contribution of industrial sources. Industry is the only segment of the total environment which has and is developing a full hearing conservation program. Evaluation of noise as an annoyance factor and one subjective response has not received adequate study for setting of meaningful criteria. Community noise control is based too often on possible effects rather than proven effects. Most studies to evaluate the subjective response to noise have been based on aircraft noise, and attempts to rate annoyance in terms of a physical measurement. Several such rating systems are discussed. Community noise regulations tend toward zoning laws with performance standards which present many pitfalls and inconsistencies. A stepwise approach to community noise control giving due consideration to all contributing sour...