Experimental Studies on the Effects of Nozzle Structures on Characteristics of Submerged Gas Jet Noise

2012 ◽  
Vol 204-208 ◽  
pp. 4620-4623 ◽  
Author(s):  
Zong Rui Hao ◽  
Zhong Hai Zhou
Keyword(s):  
Cross Sections ◽  
Sound Pressure ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Jet Noise ◽  
Gas Jet ◽  
Frequency Bands ◽  
Sound Levels ◽  
Sound Pressure Levels ◽  
Liquid Flows

The structures of nozzle outlet have great effects on jet noise generated by submerged gas jet. Five nozzles with different cross-sections were designed to study the influences of nozzle structures on sound levels by experimental methods. The flow characteristics and sound pressure levels were measured and the gas-liquid flows formed by submerged gas jets under different Weber numbers were also observed. The results show that the gas-liquid flows transformed from bubbling regime to jetting regime with the increase of Weber numbers. With respect to bubbling flow, no significant differences in sound levels for different nozzles were found. However, a remarkable increase of acoustic emission was caused by the transformation of flow patterns over the frequency bands of 0.6-4 kHz for all nozzles. In addition, sound pressure levels for elliptical nozzle were much lower than those of other nozzles over the frequency bands of 0.6-4 kHz. Therefore, it would be a reasonable strategy to adopt several elliptical orifices instead of round nozzle to reduce the gas jet noise in the design of underwater exhaust muffler.

DEVELOPMENT OF THE METHODOLOGY FOR MEASURING NOISE LEVELS IN THE UNDERGROUND ROLLING STOCK

Akustika ◽  
2021 ◽  
pp. 183
Author(s):  
Aleksandr Shashurin ◽  
Konstantiv Fiev ◽  
Viktoriia Vasilyeva ◽  
Andrey Voronkov
Keyword(s):  
Sound Pressure ◽  
Rolling Stock ◽  
Noise Levels ◽  
Noise And Vibration ◽  
Frequency Bands ◽  
Sound Levels ◽  
Digital Spectrum ◽  
Sound Pressure Levels ◽  
Noise Measurements ◽  
Underground Railway

This document specifies the methodology for measuring equivalent sound pressure levels in octave frequency bands (in dB rel. 20 μPa), equivalent and maximum A-corrected sound levels (in dB rel. to 20 μPa), generated in the rolling stock in the driver’s cabins and in the passenger rooms of the salons, using acoustic meters - multifunctional analyzers Ecophysics, noise and vibration meters, spectrum analyzers Ecophysics 110A, Oktava 110A Eco, Oktava 110A, Oktava 111, B&K 2250, 2250L, 2270, noise and vibration analyzers ASSISTANT, noise and vibration meters, digital spectrum analyzers Algorithm-05, SVAN979. This methodology is applicable for noise measurements in the driver’s cabins and in the passenger rooms of the rolling stock of both new and old models operated by the underground railway.

scholarly journals Automotive traffic noise and urban public spaces

2021 ◽  
Vol 9 (72) ◽  
Author(s):  
Greicikelly Gaburro Paneto ◽  
Cristina Engel de Alvarez ◽  
Paulo Henrique Trombetta Zannin
Keyword(s):  
Urban Space ◽  
Sound Pressure ◽  
Traffic Noise ◽  
Motor Vehicles ◽  
Open Spaces ◽  
Sound Levels ◽  
Measurement Results ◽  
Sound Pressure Levels ◽  
High Sound

In contemporary cities, and usually without realizing it, the population has been exposed to high sound pressure levels, which besides causing discomfort, can lead to health problems. Considering that a large part of this noise comes from emission from motor vehicles, this research aims to evaluate the sound behavior in sound environments configured by voids in the urban fabric, in order to identify whether open spaces can act as attenuators of sound levels. To obtain the expected results, the methodology used was structured from a review of the state-of-the-art and computer simulations relating the variables that influence the formation of urban space and sound emission and propagation, taking as a case study an urban portion of the municipality of Vitória/ES. In parallel, questionnaires were applied to evaluate the user's perception of their exposure. The measurement results indicated that the sound pressure levels caused by traffic noise are above the limit tolerated limit by the NBR norm 10151:2000 for the daytime period. In turn, the results obtained from the population indicated that there is little perception of noise by the users of the spaces surveyed.

Assessment of Environmental Noise and Air Quality in Critical Areas at UiTM Engineering Complex

2013 ◽  
Vol 471 ◽  
pp. 125-129
Author(s):  
N.V. David ◽  
K. Ismail
Keyword(s):  
Air Quality ◽  
Sound Pressure ◽  
Quality Measurement ◽  
Environmental Noise ◽  
Sound Level ◽  
Public Parks ◽  
Noise Sources ◽  
Critical Areas ◽  
Sound Levels ◽  
Sound Pressure Levels

Excessive environmental noise and poor air quality can be adverse to human health, living comfort and the environment itself. Measurement of sound pressure levels and air quality in critical areas including libraries, campus areas, public parks and hospitals thus becomes necessary to monitor and mitigate existing noise levels. In a university environment, student activities will be less disrupted if the locations of the activities are sufficiently away from noise sources. The present study is intended to measure sound levels and air quality around the Engineering Complex, Universiti Teknologi Mara, Shah Alam. The measured data is compared with to acceptable sound pressure levels and air quality index specified by the Department of Environment (DOE), Malaysia. Sound pressure levels are measured using the Castle Sound Level Meter Type 6224 and air quality measurement was done by using the BW Gas Alert MicroClip XT device. Both measurements were conducted at five selected stations around the Engineering Complex for three times each weekday for five weeks. Results obtained indicated that sound levels at some locations and time zones are above the thresholds recommended by the DOE. The air quality is acceptable in most locations except the vicinity of a bus stop. With the growing number of students in the university and other factors like construction and redevelopment of existing roads, a continuously increasing noise situations and air pollution proportional to the traffic flow is inevitable.

EXPERIMENTAL STUDIES ON THE NOISE AND VIBRATION OF A SPECIAL BORING MACHINE DUE TO FORMATION OF THE OPERATOR´S WORKPLACE SOUND FIELD

Akustika ◽  
2019 ◽  
Vol 34 ◽  
pp. 100-103
Author(s):  
Alexander Shashurin ◽  
Marat Goguadze ◽  
Anna Lubianchenko
Keyword(s):  
Theoretical Analysis ◽  
Sound Pressure ◽  
Experimental Studies ◽  
Sound Radiation ◽  
Sound Field ◽  
Noise Levels ◽  
Noise And Vibration ◽  
Measurement Results ◽  
Sound Pressure Levels ◽  
Excessive Noise

The purpose of this study is to measure the octave sound pressure levels and vibrations of a boring machine. A theoretical analysis of the sound pressure levels near the boring machine is performed. The measurement results are given. It was found that the workplace sound pressure levels exceed the sanitary standards, which suggests that the excessive noise levels are due to the exposure to the cutter sound radiation and the axis being machined.

Sound Exposure of Healthcare Professionals Working with a University Marching Band

2018 ◽  
Vol 29 (01) ◽  
pp. 083-089
Author(s):  
Jeffrey A. Russell ◽  
Moegi Yamaguchi
Keyword(s):  
Performing Arts ◽  
Sound Pressure ◽  
Healthcare Providers ◽  
Marching Band ◽  
Hearing Disorders ◽  
Sound Exposure ◽  
Band Music ◽  
Sound Levels ◽  
Marching Bands ◽  
Sound Pressure Levels

AbstractMusic-induced hearing disorders are known to result from exposure to excessive levels of music of different genres. Marching band music, with its heavy emphasis on brass and percussion, is one type that is a likely contributor to music-induced hearing disorders, although specific data on sound pressure levels of marching bands have not been widely studied. Furthermore, if marching band music does lead to music-induced hearing disorders, the musicians may not be the only individuals at risk. Support personnel such as directors, equipment managers, and performing arts healthcare providers may also be exposed to potentially damaging sound pressures. Thus, we sought to explore to what degree healthcare providers receive sound dosages above recommended limits during their work with a marching band.The purpose of this study was to determine the sound exposure of healthcare professionals (specifically, athletic trainers [ATs]) who provide on-site care to a large, well-known university marching band. We hypothesized that sound pressure levels to which these individuals were exposed would exceed the National Institute for Occupational Safety and Health (NIOSH) daily percentage allowance.Descriptive observational studyEight ATs working with a well-known American university marching band volunteered to wear noise dosimeters.During the marching band season, ATs wore an Etymotic ER-200D dosimeter whenever working with the band at outdoor rehearsals, indoor field house rehearsals, and outdoor performances. The dosimeters recorded dose percent exposure, equivalent continuous sound levels in A-weighted decibels, and duration of exposure. For comparison, a dosimeter also was worn by an AT working in the university’s performing arts medicine clinic. Participants did not alter their typical duties during any data collection sessions. Sound data were collected with the dosimeters set at the NIOSH standards of 85 dBA threshold and 3 dBA exchange rate; the NIOSH 100% daily dose is an exposure to 85 dBA over 8 h. Dose data for each session were converted to a standardized dose intensity by dividing the dose percentage by the duration of the exposure and setting the NIOSH standard as a factor of 1.0. This allowed convenient relative comparisons of dose percentages of vastly different exposure durations. Analysis of variance examined relationships of noise exposures among the venues; post hoc testing was used to assess pairwise differences.As hypothesized, ATs were exposed to high sound pressure levels and dose percentages greatly exceeding those recommended by NIOSH. Higher sound levels were recorded in performance venues compared with rehearsal venues. In addition to the band music, crowd noise and public address systems contribute to high sound levels at performances.Our results suggest that healthcare providers working with marching bands are exposed to dangerous levels of sound during performances. This is especially true at venues such as football stadiums, where crowd noise and public address systems add to sound pressure. A hearing conservation program, including protection, should be required for all healthcare staff who work with marching bands. Moreover, our results should inform hearing conservation practices for marching musicians, directors, and support personnel.

Subsonic Flow Over Open Cavities: Part 2 — Passive Control Methods

2016 ◽  
Author(s):  
Weidong Shao ◽  
Jun Li
Keyword(s):  
Sound Pressure ◽  
Passive Control ◽  
Subsonic Flow ◽  
Dynamic Pressure ◽  
Flow Characteristics ◽  
Leading Edge ◽  
Control Methods ◽  
Trailing Edge ◽  
Open Cavities ◽  
Sound Pressure Levels

A global description of the intrinsic instabilities of shear layer for further understanding of the aeroacoustical oscillation of subsonic flow over open cavities has been given in the companion paper. The needs to suppress dynamic pressure loads in open cavities play an important role in many aeronautical applications. Large eddy simulation (LES) of passive control methods including recessed leading edge step and sloping trailing edge wall arrangements is performed. The unsteady flow characteristics and aeroacoustical oscillation mechanism of baseline cavity are given in advance. Effects of both passive control methods on resonant frequency and sound pressure levels are demonstrated and analyzed. Recessed leading edge step tends to decrease the resonant Strouhal numbers and the maximal reduction of overall sound pressure levels (OASPL) reaches 8.5dB. Sloping trailing edge wall reduces OASPL by shifting down the impinging location on cavity back wall. The optimal reduction of OASPL arrives at 11dB when the angle of inclination is maximal. The drag induced by cavity flows is found to be highly correlated with dynamic loads on cavity walls.

Montevideo, walkable city: pedestrianization of a large avenue during 2020 pandemic

2021 ◽  
Vol 263 (5) ◽  
pp. 1586-1593
Author(s):  
Alice Elizabeth Gonzalez ◽  
Pablo Gianoli Kovar ◽  
Lady Carolina Ramírez ◽  
Micaela Luzardo Rivero
Keyword(s):  
Sound Pressure ◽  
Sound Level ◽  
Environmental Sound ◽  
Sound Levels ◽  
Acoustic Quality ◽  
Sound Pressure Levels ◽  
The City

On March 13, 2020, the first cases of SARS-COVID19 were detected in Uruguay. During the first weeks of the pandemic, mobility was significantly reduced with the slogan "If you can, stay home"; it was not a mandatory but voluntary confinement. After a couple of months, there was a big drop in the number of people affected by the disease. Thus, the Municipality of Montevideo, betting on a more human and walkable city, defined that the main avenue of the city had a pedestrian section on Saturday afternoons. This resulted in a greater enjoyment of the city by its inhabitants, as they had more space to walk while maintaining safe distances between people. It was also possible to promote trading, since classically Ave. 18 de Julio is also a commercial stroll. Additionally, the sound pressure levels recorded by the Municipality's stationary sound level meters located at three points along the avenue, showed the reduction of environmental sound levels in pedestrian areas, improving the acoustic quality of the walk. In this paper, sound pressure levels on Saturday afternoons at different times of the year before, during and after the initial lockdown due to the COVID-19 pandemic, are compared and discussed.

THEORETICAL STUDY OF NOISE GENERATION DURING DRILLING OF WOOD WORKPIECES WITH REGARD TO THE DRILL FEED RATE

Akustika ◽  
2021 ◽  
pp. 183-185
Author(s):  
Dmitry Ruslyakov
Keyword(s):  
Feed Rate ◽  
Metal Cutting ◽  
Sound Pressure ◽  
Theoretical Study ◽  
Experimental Studies ◽  
Drilling Process ◽  
Noise Generation ◽  
Circular Saw ◽  
Sound Pressure Levels ◽  
Milling Machines

In contrast to metal-cutting machines, woodworking machines are characterized not only by sound pressure levels at the operators’ workplaces that exceed the sanitary standards, but also by dust concentrations that also exceed the standards. At present, a set of theoretical and experimental studies has been carried out and engineering solutions have been proposed to bring vibroacoustic characteristics and dustiness to the sanitary standards for woodworking thickness-jointing machines, band and circular saw machines, model and contour-milling machines. Studies of this kind in relation to woodworking drilling machines have not been done. It should be noted that not only the layout of woodworking drilling machines, but also the dynamics of the drilling process has significant differences from the above mentioned machines.

Acoustic and Vibration Analysis of Fluid Induced Blower and Piping Unwanted Motion

2011 ◽  
Author(s):  
Ned M. Endres
Keyword(s):  
Sound Pressure ◽  
Check Valve ◽  
Operating Conditions ◽  
Piping System ◽  
Vibration Measurements ◽  
System A ◽  
Sound Levels ◽  
Sound Pressure Levels ◽  
Air Blower ◽  
High Sound

This paper presents investigational findings and a discussion of recommendations relating to sound and vibration measurements performed in connection with a fluid induced vibration issue on two air blowers and attached exhaust piping at an industrial facility. These vibration and sound measurements were prompted by recent check valve failures for the air blower units, and unacceptable sound levels emanating from these units and affecting nearby residents. This data was acquired during steady state operating conditions of the blowers under normal operating conditions. An FFT data acquisition system, a piezoelectric microphone and three piezoelectric triaxial accelerometers were used to collect vibration measurements at each of the 70 locations on the blowers, motors, blower bases, and exhaust piping, while sound measurements were simultaneously acquired with the microphone. Piping and blower vibration readings were used to construct an operating deflection shape analysis of the blowers, foundations and attached piping system. The resulting vibration and sound analysis revealed that acoustic excitation of the piping system appeared to be the likely source of the high vibration, high sound pressure levels; piping cracks and check valve failures. Corrective actions were implemented that reduced the sound pressure levels, vibration levels, and reduced/eliminate the piping damage and valve failures.

Characterization of Noise in Eating Establishments Based on Psychoacoustic Parameters

2019 ◽  
Vol 887 ◽  
pp. 539-546 ◽  
Author(s):  
Onurcan Çakir ◽  
Zeynep Sevinç ◽  
Mustafa Emre İlal
Keyword(s):  
Sound Pressure ◽  
Sound Recordings ◽  
Lombard Effect ◽  
Architectural Acoustics ◽  
Noise Characteristics ◽  
Sound Levels ◽  
Sound Pressure Levels ◽  
Institute Of Technology ◽  
The Relationship

Noise in eating establishments has been studied in architectural acoustics literature. For evaluating acoustics in these spaces, researchers predominantly investigate sound pressure levels and reverberation times. Yet, noise in eating spaces originate from a wide variety of sources and is hard to describe and evaluate with only sound pressure levels and reverberation times. Better metrics for acoustics in closed public spaces are needed. Psychoacoustic parameters of loudness, sharpness, fluctuation strength and roughness are promising metrics that have been used by many recent studies evaluating noise annoyance. However, unlike the established metrics such as reverberation time, no set of recommended values exist for these parameters, yet. The aim of this study is to investigate noise in eating establishments through psychoacoustic parameters and understand both the noise characteristics and the metrics themselves. This paper presents a set of sound recordings during lunch hours in two eating spaces in Izmir Institute of Technology. The entry and egress of occupants have been tracked manually, while sound levels have been measured and the noise has been recorded for psychoacoustics analysis. The relationship between the number of occupants and psychoacoustic parameters has been investigated through these objective measurements. The relationship between the number of occupants and sound levels is discussed in the light of the Lombard effect.

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