Noise Control on Diesel Tugs

1973 ◽  
Vol 10 (04) ◽  
pp. 321-333
Author(s):  
Thomas R. Dyer ◽  
Bertel Lundgaard
Keyword(s):  
Noise Level ◽  
Noise Suppression ◽  
Noise Control ◽  
Noise Generation ◽  
Noise Levels ◽  
Paper Briefly ◽  
Acoustic Treatment

The paper briefly gives basic acoustic definitions and explains the fundamental concepts used in noise control. The mechanics of noise generation and the various methods used in noise suppression are explained. The silencing program employed on two sister tugs, Edith Lovejoy and Anne Carlander, is described in detail. The acoustic treatment of the tugs is not identical and the resulting noise level differences are discussed. Alternative acoustic approaches are described and evaluated. The paper is illustrated with graphs and tables of noise levels, and shows typical vessel arrangements and acoustic treatment details. A short bibliography is included.

scholarly journals Aspects of Gas Turbine Noise Control in the Vicinity of Residential Areas

1987 ◽  
Author(s):  
Friedrich Fleischer
Keyword(s):  
Environmental Protection ◽  
Gas Turbine ◽  
Noise Level ◽  
Noise Control ◽  
Control Measures ◽  
Residential Areas ◽  
Noise Levels ◽  
Turbine Plant ◽  
Gas Turbine Plant

This paper deals with problems of noise control involving gas turbine plants, particularly where they are installed near residential areas already subject to noise nuisance. Noise control measures for existing industrial or power-generating plant are often designed to achieve an overall immitted noise level only marginally below the legal maximum. Considerably enhanced measures are thus required for additional plant. However, the noise from a gas turbine plant has numerous individual sources and it is shown that a differentiated approach is required. Generally, progressive reductions in noise levels involve disproportionately greater increases in expenditure on appropriate measures. Stringent environmental protection requirements necessitate cost-intensive solutions.

Global Active Noise Control of a One-Dimensional Acoustic Duct Using a Feedback Controller

1993 ◽  
Vol 115 (3) ◽  
pp. 488-494 ◽  
Author(s):  
A. J. Hull ◽  
C. J. Radcliffe ◽  
S. C. Southward
Keyword(s):  
Noise Level ◽  
Noise Control ◽  
Acoustic Noise ◽  
Active Noise Control ◽  
Decay Rates ◽  
Pole Placement ◽  
Noise Levels ◽  
One Dimensional ◽  
Active Noise ◽  
System Pressure

Active noise control of acoustic enclosures is a classical engineering problem. The active noise control of a one-dimensional hard-walled duct with a partially dissipative boundary condition is addressed in this paper. Previous techniques have attacked this problem by developing adaptive filters designed to cancel acoustic noise at a single measurement location. The work presented here applies modern, state space, control theory to globally reduce noise levels in a one-dimensional acoustic enclosure rather than at a single location. This global control requires only the addition of a single response measurement microphone and control speaker to the open-loop system. Pressure measurements are taken at the microphone location and passed to an observer, which generates estimates of the system states. Using these state estimates, a pole placement feedback control algorithm is used to lower the noise level. Pole placement reduces noise levels globally by increasing the decay rates of all the controlled acoustic states. Experimental results presented here demonstrate reduction in the noise level at all points in the duct by 58 percent when the system is excited by random amplitude pressure input.

The Noise-Producing Characteristics of Highly Loaded, Valveless, Pulse Combustors

1988 ◽  
Vol 110 (2) ◽  
pp. 238-245 ◽  
Author(s):  
J. A. C. Kentfield
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Noise Suppression ◽  
Analytical Data ◽  
Velocity Profiles ◽  
Noise Generation ◽  
Noise Levels ◽  
Transient Velocity ◽  
Inherent Problem ◽  
Frequency Pulse

An inherent problem of pulsating combustors is noise generation and the difficulty of predicting noise levels. Analytical data are presented which illustrate the transient velocity profiles prevailing at the open ends of the inlets and tailpipes of valveless pulse combustors. A comparison is made of measured sound pressure level spectra at these locations with corresponding predicted transient velocity profiles. It is shown that there is a correlation of the main characteristics of the noise spectra and velocity profiles. Consideration is also given to the problems of muffling valveless pulse combustors and the potential, from the noise suppression viewpoint, of twin-coupled units and relatively high frequency pulse combustors featuring multiple inlet passages. An indication is also given of how it may be possible to operate clusters, or arrays, of pulse combustors firing sequentially.

scholarly journals Problems of acoustic safety in power engineering

2022 ◽  
Vol 2150 (1) ◽  
pp. 012022
Author(s):  
V B Tupov ◽  
A A Taratorin ◽  
V S Skvortsov ◽  
A B Mukhametov
Keyword(s):  
Gas Turbine ◽  
Noise Level ◽  
Noise Suppression ◽  
Environmental Safety ◽  
Combined Cycle ◽  
Power Engineering ◽  
Excess Noise ◽  
Noise Levels ◽  
Protection Zone ◽  
Safety Issues

Abstract Environmental safety issues are becoming increasingly important in the life of society. Among environmental safety issues in power engineering, acoustic safety occupies a special place. The problem of acoustic safety is associated with the fact that the regular operation of power equipment leads to an increased noise level, and power facilities are located in close proximity to residential areas. In this work, acoustic calculations were performed to determine the sanitary protection zone for gas turbines units (GTU) and combined cycle gas turbine units (CCGT) of various capacities. A formula was obtained for calculating the width of the sanitary protection zone depending on the capacity of gas turbine units and combined cycle plants and their number. It is shown that the sanitary protection zone (SPZ) of a power unit of high capacity is smaller than the sanitary protection zone of several power units of the same capacity. It is found that the noise levels from individual groups of equipment can determine the noise level at the entire border of the sanitary protection zone or in its individual sections. At the same time, noise suppression measures should be taken for all sources that generate noise levels in excess of standards. It is necessary to start noise suppression measures from those sources that generate excess noise in a larger section of the sanitary protection zone.

scholarly journals Noise in Otolaryngology – Head and Neck Surgery operating rooms: a systematic review

2021 ◽  
Vol 50 (1) ◽  
Author(s):  
Gianluca Sampieri ◽  
Amirpouyan Namavarian ◽  
Marc Levin ◽  
Justine Philteos ◽  
Jong Wook Lee ◽  
...  
Keyword(s):  
Systematic Review ◽  
Head And Neck ◽  
Patient Outcomes ◽  
Noise Level ◽  
Neck Surgery ◽  
Operating Rooms ◽  
Head And Neck Surgery ◽  
Noise Levels ◽  
Surgical Performance ◽  
The Mean

Abstract Objective Noise in operating rooms (OR) can have negative effects on both patients and surgical care workers. Noise can also impact surgical performance, team communication, and patient outcomes. Such implications of noise have been studied in orthopedics, neurosurgery, and urology. High noise levels have also been demonstrated in Otolaryngology-Head and Neck Surgery (OHNS) procedures. Despite this, no previous study has amalgamated the data on noise across all OHNS ORs to determine how much noise is present during OHNS surgeries. This study aims to review all the literature on noise associated with OHNS ORs and procedures. Methods Ovid Medline, EMBASE Classic, Pubmed, SCOPUS and Cochrane databases were searched following PRISMA guidelines. Data was collected on noise measurement location and surgery type. Descriptive results and statistical analysis were completed using Stata. Results This search identified 2914 articles. Final inclusion consisted of 22 studies. The majority of articles analyzed noise level exposures during mastoid surgery (18/22, 82%). The maximum noise level across all OHNS ORs and OHNS cadaver studies were 95.5 a-weighted decibels (dBA) and 106.6 c-weighted decibels (dBC), respectively (P = 0.2068). The mean noise level across all studies was significantly higher in OHNS cadaver labs (96.9 dBA) compared to OHNS ORs (70.1 dBA) (P = 0.0038). When analyzed together, the mean noise levels were 84.9 dBA. Conclusions This systematic review demonstrates that noise exposure in OHNS surgery exceeds safety thresholds. Further research is needed to understand how noise may affect team communication, surgical performance and patient outcomes in OHNS ORs. Graphical abstract

Effective splicing localization based on noise level inconsistencies

2021 ◽  
pp. 1-11
Author(s):  
P. N. R. L. Chandra Sekhar Author ◽  
T. N. Shankar Author
Keyword(s):  
Digital Technology ◽  
Social Networking Sites ◽  
Noise Level ◽  
Research Work ◽  
Multimedia Content ◽  
Noise Levels ◽  
Multimedia Forensics ◽  
The Past ◽  
Photo Editing ◽  
State Of Art

In the era of digital technology, it becomes easy to share photographs and videos using smartphones and social networking sites to their loved ones. On the other hand, many photo editing tools evolved to make it effortless to alter multimedia content. It makes people accustomed to modifying their photographs or videos either for fun or extracting attention from others. This altering brings a questionable validity and integrity to the kind of multimedia content shared over the internet when used as evidence in Journalism and Court of Law. In multimedia forensics, intense research work is underway over the past two decades to bring trustworthiness to the multimedia content. This paper proposes an efficient way of identifying the manipulated region based on Noise Level inconsistencies of spliced mage. The spliced image segmented into irregular objects and extracts the noise features in both pixel and residual domains. The manipulated region is then exposed based on the cosine similarity of noise levels among pairs of individual objects. The experimental results reveal the effectiveness of the proposed method over other state-of-art methods.

scholarly journals Characterization of Noise Level Inside a Vehicle under Different Conditions

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2471 ◽  
Author(s):  
Daniel Flor ◽  
Danilo Pena ◽  
Luan Pena ◽  
Vicente A. de Sousa ◽  
Allan Martins
Keyword(s):  
Regression Analysis ◽  
Noise Level ◽  
Acoustic Noise ◽  
Experimental Setup ◽  
Strongly Correlated ◽  
Noise Levels ◽  
Noise Sources ◽  
Statistical Tools ◽  
Window Position

Vehicular acoustic noise evaluations are a concern of researchers due to health and comfort effects on humans and are fundamental for anyone interested in mitigating audio noise. This paper focuses on the evaluation of the noise level inside a vehicle by using statistical tools. First, an experimental setup was developed with microphones and a microcomputer located strategically on the car’s panel, and measurements were carried out with different conditions such as car window position, rain, traffic, and car speed. Regression analysis was performed to evaluate the similarity of the noise level from those conditions. Thus, we were able to discuss the relevance of the variables that contribute to the noise level inside a car. Finally, our results revealed that the car speed is strongly correlated to interior noise levels, suggesting the most relevant noise sources are in the vehicle itself.

Noise Pollution in Onitsha Metropolis: Challenges and Solution

2021 ◽  
Vol 1 (2) ◽  
pp. 032-040
Author(s):  
Chris Onyeka Ekweozor ◽  
Johnbosco Emeka Umunnakwe ◽  
Leo O Osuji ◽  
Vincent C Weli
Keyword(s):  
State Government ◽  
Noise Level ◽  
Control Point ◽  
Noise Pollution ◽  
Health Impact ◽  
Dry Season ◽  
Noise Levels ◽  
Wet Season ◽  
High Noise ◽  
Anambra State

This study evaluated noise pollution in Onitsha metropolis, Anambra State, Nigeria in 2019. Noise levels were measured at forty sampling stations in the morning, afternoon and night within the study area for dry and wet seasons using modern noise level instruments. A control point was established at ldeani/Nnobi Junction with coordinates N 06o 05’.282’’ E 006o 55’.891’’ which was used as a reference point and for comparison with the sound levels recorded in designated locations. The results showed that the maximum noise level in the study area exceeded the Federal Ministry of Environment (FMEnv) limit by 7.8% in the dry season and by 13.11% in the wet season. Noise LAeq exceeded the NESREA LAeq limit by 29.89% in the dry season and by 33.44% in the wet season. The study indicated that the mean noise levels in the dry and wet seasons were within FMEnv limit of 90dB .It also showed that high noise levels were recorded around major junctions and market places within Onitsha, which are harmful to public health. The study further showed that transportation activities and trading activities at the market places are the main sources of high noise levels in the study area. Health impact assessment should be conducted in Onitsha metropolis for residents. State government should enforce compliance laws and regulate the activities of industries in the areas.

The variability of naturally occurring magnetic field levels: 10 Hz to 8 kHz

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. F187-F197 ◽  
Author(s):  
Ben K. Sternberg
Keyword(s):  
Magnetic Field ◽  
Noise Level ◽  
Monsoon Season ◽  
Signal Frequency ◽  
Time Interval ◽  
Frequency Range ◽  
Noise Levels ◽  
Controlled Source ◽  
Naturally Occurring ◽  
Minimum Noise

The variability of naturally occurring magnetic fields in the frequency range from [Formula: see text] over a period of one year was studied. Contour plots for the [Formula: see text], [Formula: see text], and [Formula: see text] components and for frequencies of 10, 100, 1000, 2000, and 8000 Hz were produced. Average, minimum, maximum, and the standard deviations of these fields were also calculated for 12 distinctive time intervals. In the 1– to 8–kHz frequency range, the noise levels are typically higher at night. In the 10- to 100-Hz frequency range, the noise levels are typically higher during the day. During mid- to late-summer, there is frequent thunderstorm activity, known in the southwest United States as the monsoon season. The magnetic field levels are often very high during this time period. These variability ranges can be used to estimate the lowest levels of noise that may be encountered during field surveys, which iswhat the authors are looking for when running controlled-source electrical method surveys. These variability ranges can also be used to estimate the highest levels that may be encountered, which is what the authors are looking for when running natural-source electrical methods surveys, such as audio frequency magnetotelluric (AMT) surveys. These measurements of magnetic field strength variability show that better data for controlled-source electrical measurements can be obtained using the minimum noise level measurements, as opposed to using signal integration or signal averaging with all of the data. The minimum noise level is found by using frequency bins adjacent to the signal-frequency bin. Likewise, if one is interested in measuring the naturally occurring magnetic field data, using the maximum values during each time interval makes AMT measurements possible when the natural signal level is very low, particularly in the AMT dead zone around [Formula: see text].

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