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Results for “noise exposure”

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At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

NASA NTRS1983

Evaluation of human exposure to the noise from large wind turbine generators

The human perception of a nuisance level of noise was quantified in tests and attempts were made to define criteria for acceptable sound levels from wind turbines. Comparisons were made between the sound necessary to cause building vibration, which occurred near the Mod-1 wind turbine, and human perception thresholds for building noise and building vibration. Thresholds were measured for both broadband and impulsive noise, with the finding that noise in the 500-2000 Hz region, and impulses with a 1 Hz fundamental, were most noticeable. Curves were developed for matching a receiver location with expected acoustic output from a machine to determine if the sound levels were offensive. In any case, further data from operating machines are required before definitive criteria can be established.

Shepherd, K. P.↗

NASA NTRS1972

Noise suppression by time exposure oscilloscope photography.

We describe a simple and inexpensive means of enhancing repetitive signals obscured by noise with roughly equal amplitude. The signal and noise are displayed on an oscilloscope, and we perform a time average over many traces by time exposure photography. If the oscilloscope triggering is synchronous with the signal, the result is a significant suppression of the offending noise.

Huchital, G. S.↗

NASA NTRS1975

JPL noise control program

Exposures of personnel to noise pollution at the Jet Propulsion Laboratories, Pasadena, California, were investigated. As a result of the study several protective measures were taken: (1) employees exposed to noise hazards were required to wear ear-protection devices, (2) mufflers and air diversion devices were installed around the wind tunnels; and (3) all personnel that are required to wear ear protection are given annual audimeter tests.

Klascius, A. F.↗

NASA NTRS1981

Effects of noise frequency on performance and annoyance for women and men

Effects of noise frequencies on both performance on a complex psychomotor task and annoyance were investigated for men (n = 30) and women (n = 30). Each subject performed a complex psychomotor task for 50 min in the presence of low-frequency noise, high-frequency noise, or ambient noise. Women and men learned the task at different rates. Little effect of noise was shown. Annoyance ratings were subsequently obtained from each subject for noises of various frequencies by the method of magnitude estimation. High-frequency noises were more annoying than low-frequency noises regardless of sex and immediate prior exposure to noise. Sex differences in annoyance did not occur. No direct relationship between learning to perform a complex task while exposed to noise and annoyance by that noise was demonstrated.

Key, K. F.↗

NASA NTRS1981

Evaluation of integral exposure energy load on aural analyzer of miners

The individual exposure integral noise load on workers before the beginning of hearing impairment was determined for a group of 20 male miners who had worked with drilling equipment and harvesters for 8 to 20 years before the onset of the disability. Results show that the total exposure energy load of about 4 kw x h sq m, obtained by miners in the examined group, resulted in occupational injury to the auditory organ (cochlear neuritis) in 75% of the cases. The equivalent energy level of noise computed according to the date of total energy load is roughly 99 db A, which significantly exceeds the permissible amount of 85 db A. There is a correlation (r = 0.77) between the integral exposure energy noise on the aural analyzer in the degree of increase in the total threshold for the mean speech range.

Kornilov, A. N.↗

NASA NTRS1974

Coherent optical noise suppression device

The present work describes a scheme for a noise suppression system to be used with an afocal coherent optical data processor. The noise averaging scheme is based on the simple principle of moving input and output film planes together during exposure; the noise pattern remains stationary while the desired (filtered) image moves through it. The noise suppression system consists of a drive motor, right-angle gear box, reversing gear assemblage, right-angle gear drive, and micrometer adjusting translation tables. The device was tested by using a Sayce target containing fundamental spatial frequencies from 5 lines/mm to 100 lines/mm as the input signal. The output was photographed on Pan-X 35-mm film with and without the noise suppression system in operation. Microdensitometer scans of the exposed output film show that without noise averaging, resolution is good to about 80 lines/mm, while with noise averaging, it is good to about 35 lines/mm. A brief analysis of errors in the mechanical parts of the system reponsible for the upper limit of resolution is presented.

Horner, J. L.↗

NASA NTRS1981

Extracting spatial information from large aperture exposures of diffuse sources

The spatial properties of large aperture exposures of diffuse emission can be used both to investigate spatial variations in the emission and to filter out camera noise in exposures of weak emission sources. Spatial imaging can be accomplished both parallel and perpendicular to dispersion with a resolution of 5-6 arc sec, and a narrow median filter running perpendicular to dispersion across a diffuse image selectively filters out point source features, such as reseaux marks and fast particle hits. Spatial information derived from observations of solar system objects is presented.

Clarke, J. T.↗

NASA NTRSDate not supplied

Estimating the Noise Floor of Sonic Boom Metrics Across the USA

NASA is building the X-59 Quiet Supersonic Technology aircraft to produce low noise sonic booms for a series of community noise surveys across the USA. Survey participants will rate their perception of the low booms from supersonic X-59 flyovers. Several noise metrics are proposed to quantify the noise dose: A-, B-, D-, E-weighted Sound Exposure Level, Stevens Perceived Level, and Indoor Sonic Boom Annoyance Predictor. Sparse measurements across the survey area will be used to estimate community noise exposure. The level of these low booms may be comparable to the ambient noise level in some locations, leading to uncertainty in noise exposure estimations. This uncertainty may necessitate increased reliance on sonic boom propagation predictions for exposure estimation. Low-boom signal to ambient noise ratio is one way to quantify uncertainty in measured sonic boom levels. An empirical relationship between A-weighted ambient level and sonic boom metric levels is used in conjunction with the National Park Service’s L50 SPL map to estimate sonic boom metric ambient levels across the USA. The estimate of ambient sonic boom metric levels will aid in X-59 test planning and execution.

sonic boom↗

NASA NTRS2021

Estimated Ambient Sonic Boom Metric Levels and X-59 Signal-to-Noise Ratios across the USA

NASA is building the X-59 Quiet Supersonic Technology aircraft to produce low noise sonic booms for a series of community noise surveys across the USA. Survey participants will rate their perception of the low-booms from supersonic X-59 flyovers. Several noise metrics are proposed to quantify the noise dose: A-, B-, D-, and E-weighted Sound Exposure Level, Stevens Perceived Level, and Indoor Sonic Boom Annoyance Predictor. Sparse measurements across the survey area will be used to estimate community noise exposure. The level of these low-booms may be comparable to the ambient noise level in some locations, leading to uncertainty in noise exposure estimations. This uncertainty may necessitate increased reliance on sonic boom propagation predictions for exposure estimation. Low-boom signal to ambient noise ratio is one way to quantify uncertainty in measured sonic boom levels. An empirical relationship between A-weighted ambient level and sonic boom metric levels is used in conjunction with the National Park Service’s L50 SPL map to estimate ambient noise levels expressed in terms of sonic boom noise metrics across the USA. These estimates of ambient levels will aid in X-59 community test planning and execution. The signal-to-noise ratio for the undertrack X-59 sonic boom is also estimated, and an example application of these data is presented for comparing potential noise monitor sites prior to a community noise test.

X-59↗

NASA NTRS1974

Level, peculiarities and effects of coal mine noise on pit workers

There exists a correlation between noise intensity and spectrum and degree of hearing impairment in the different professional categories in the pit. Most affected are dross miners and drillers. In these, the first degree of hypoacusia sets in within the first five years of exposure. Deafness begins at a frequency of 4,000 Hz, but often enough (20%) at 2,000 Hz as well, progressively evolving through the classical stages if exposure to noise continues. In the coal bearing basins investigated, the noise level is, on the whole, 31.2%, but the conventional zone is not involved by more than 6.3%. Technological and medical measures are proposed for the purpose of avoiding these troubles in the future.

Darlea, I. G.↗

NASA NTRS2024

Perceptual Evaluation of Sound Exposure Level in Annoyance Ratings to Helicopter Noise

A psychoacoustic test was performed to assess the effectiveness of Sound Exposure Level (SEL) for indicating changes in annoyance to helicopter noise. SEL was evaluated for flyover auralizations of optimized rotor designs and for flyover recordings of different helicopters and maneuvers. The test used paired comparisons of flyovers within 10 dB of the maximum A-weighted sound pressure level. For stimuli of equal SEL, annoyance responses showed whether or not SEL is a good indicator of annoyance. While this work does not seek to determine specific attributes contributing to annoyance that are not included in SEL, the magnitude of this offset is of primary interest. Specifically, annoyance responses to relative differences in SEL allowed the calculation of an Equal Annoyance Point. Reductions in SEL lead to reductions in annoyance as expected, but for certain cases, SEL can fail to capture perceptually significant features such as audible differences due to changes in tail rotor design or unsteadiness in the sound of the helicopter.

Sound Exposure Level↗

NASA NTRS2007

Cardiac Autonomic Effects of Acute Exposures to Airborne Particulates in Men and Women

The aim of this research was to investigate cardiac autonomic changes associated with acute exposures to airborne particulates. Methods: High fidelity 12-lead ECG (CardioSoft, Houston, TX) was acquired from 19 (10 male / 9 female) non-smoking volunteers (age 33.6 +/- 6.6 yrs) during 10 minutes pre-exposure, exposure and post-exposure to environmental tobacco smoke (ETS), cooking oil fumes, wood smoke and sham (water vapor). To control exposure levels, noise, subject activity, and temperature, all studies were conducted inside an environmental chamber. Results: The short-term fractal scaling exponent (Alpha-1) and the ratio of low frequency to high frequency Heart Rate Variability (HRV) powers (LF/HF, a purported sympathetic index) were both higher in males (p<0.017 and p<0.05, respectively) whereas approximate entropy (ApEn) and HF/(LF+HF) (a purported parasympathetic index) were both lower in males (p<0.036, and p<0.044, respectively). Compared to pre-exposure (p<0.0002) and sham exposure (p<0.047), male heart rates were elevated during early ETS post-exposure. Our data suggest that, in addition to tonic HRV gender differences, cardiac responses to some acute airborne particulates are gender related.

Howarth, M. S.↗

DOE OSTI2024

Absorption of Axion Dark Matter in a Magnetized Medium

Detection of axion dark matter heavier than an meV is hindered by its small wavelength, which limits the useful volume of traditional experiments. This problem can be avoided by directly detecting in-medium excitations, whose ∼ meV – eV energies are decoupled from the detector size. We show that for any target inside a magnetic field, the absorption rate of electromagnetically coupled axions into in-medium excitations is determined by the dielectric function. As a result, the plethora of candidate targets previously identified for sub-GeV dark matter searches can be repurposed as broadband axion detectors. We find that a kg yr exposure with noise levels comparable to recent measurements is sufficient to probe parameter space currently unexplored by laboratory tests. Noise reduction by only a few orders of magnitude can enable sensitivity to the QCD axion in the ∼ 10 meV – 10 eV mass range. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Hearing Loss and Dementia

This report is an OSH-DO Safety Action Bulletin that briefly discusses the link between dementia and hearing loss. The bulletin provides some basic statistics, hearing loss protection guidelines and resources for more information on the topic.

99 GENERAL AND MISCELLANEOUS↗

NASA NTRS1985

A star camera aspect system suitable for use in balloon experiments

A balloon-borne experiment containing a star camera aspect system was designed, built, and flown. This system was designed to provide offset corrections to the magnetometer and inclinometer readings used to control an azimuth and elevation pointed experiment. The camera is controlled by a microprocessor, including commendable exposure and noise rejection threshold, as well as formatting the data for telemetry to the ground. As a background program, the microprocessor runs the aspect program to analyze a fraction of the pictures taken so that aspect information and offset corrections are available to the experiment in near real time. The analysis consists of pattern recognition of the star field with a star catalog in ROM memory and a least squares calculation. The performance of this system in ground based tests is described. It is part of the NASA/GSFC High Energy Gamma-Ray Balloon Instrument (2).

Hunter, S. D.↗

NASA NTRSDate not supplied

Simulated X-59 on- and off-Design Sonic Boom Levels in Realistic Atmospheres for Noise Dose Range Estimation

NASA is planning several community noise surveys across the USA using the X-59 low-boom aircraft. These surveys require a range of noise levels to resolve a dose-response relationship. The X-59 was designed to produce a shaped sonic boom with a Stevens’ Perceived Level (PL) of 75 dB or less across the boom carpet in a standard atmosphere. However, the X-59’s flight condition can be adjusted to produce levels other than 75 PLdB to obtain a range of doses during community testing. Simulated nearfield pressure waveforms of the X-59 C612A in its on-design condition (Mach 1.4 at 53,200 ft) and an off-design condition at a lower altitude (Mach 1.4 at 46,000 ft) were propagated using PCBoom through realistic atmospheres over the span of one year at several locations across the country. The predicted on-design and off-design boom levels and carpet widths are presented, resulting in a preliminary estimate of the dose range that the X-59 may produce. Future work is planned with additional off-design conditions to assess the true capable dose range of the X-59.

X-59↗

DOE OSTI2022

Impact Noise Monitoring at Site 9940: RD-24 Shots

The purpose of this sampling event was to determine if the observation point (inside the MFCP) could be relocated from 74 feet away to 21 feet from ground zero and to determine how much attenuation is provided by the MFCP. The MFCP provides noise attenuation to ensure Members of the Workforce (MOW) exposure to impact noise is below the Occupational Exposure Limit (OEL) of 140 dBC. The MFCP will be used for future tests under similar configurations. Please note that during each test shot, MOW was located inside MFCP that was 74 feet from ground zero and donned hearing protection (e.g., ear plugs with a minimum noise reduction rating of 23).

42 ENGINEERING↗

NASA NTRS1995

Noise-Induced Sleep Disturbance in Residences Near Two Civil Airports

A large-scale field study of noise-induced sleep disturbance was conducted in the vicinities of Stapleton International Airport (DEN) and Denver International Airport (DIA) in anticipation of the closure of the former and opening of the latter. Both indoor and outdoor measurements of aircraft and other nighttime noises were made during four time periods. Measurements were made in 57 homes located as close as feasible to the runway ends of the two airports. Sleep disturbance was measured by several indices of behaviorally confirmed awakening (button pushes upon awakening) and body movement (as measured with wrist-worn actimeters). A total of 2717 subject-nights of observations were made over the course of the study. Although average noise event levels measured outdoors decreased markedly at DEN after closure of the airport and increased slightly at DIA after its opening, indoor noise event levels varied much less in homes near both airports. No large differences were observed in noise-induced sleep disturbance at either airport. Indoor sound exposure levels of noise events were, however, closely related to and good predictors of actimetrically defined motility and arousal.

Fidell, Sanford↗