Unsteady Isentropic Flow through Ducts with Prescribed Sound Pressure Level Distribution

1995 ◽  
Vol 117 (3A) ◽  
pp. 279-284 ◽  
Author(s):  
J. G. Cherng ◽  
Tsung-Yen Na
Keyword(s):  
Sound Pressure Level ◽  
Unknown Parameter ◽  
Sound Pressure ◽  
Flow Speed ◽  
Pressure Level ◽  
Cross Sectional ◽  
Isentropic Flow ◽  
First Case ◽  
Flow Through

An analytical method for the determination of the required shape of a duct for a prescribed sound pressure level distribution is presented in this paper. The physical model involves a sound wave propagating in an unsteady flow of compressible fluids through ducts. Two cases are considered. In the first case, the channel shape, F(X), is given as either an exponential function or a linear function of the distance along the axis with an unknown parameter in the expression for F(X). The unknown parameter is determined by the prescribed ratio of the sound pressure level at the exit section of the duct to that at the entrance. In the second case, the sound pressure level is specified at every point along the length of the duct, and the duct shape, F(X), is sought. The governing differential equations of the model are presented. The method of complex superposition is used to separate the real and the imaginary parts of the perturbation quantities. The results show that the cross-sectional area is sensitive to the flow speed and the frequency of the sound source. Furthermore, a convergent/divergent duct has to be used to achieve a linear sound pressure level distribution.

scholarly journals Investigation of Noise Pollution Distribution in Different Parts of Yazd Textile Factories

2021 ◽  
Author(s):  
Mohammad Javad Zare Sakhvidi ◽  
Hamideh Bidel ◽  
Ahmad Ali Kheirandish
Keyword(s):  
Occupational Exposure ◽  
Sound Pressure Level ◽  
Textile Industry ◽  
Sound Pressure ◽  
Noise Pollution ◽  
Sound Level ◽  
Pressure Level ◽  
Cross Sectional ◽  
Sound Pressure Levels ◽  
Different Parts

 Background: Chronic occupational exposure to noise is an unavoidable reality in the country's textile industry and even other countries. The aim of this study was to compare the sound pressure level in different parts of the textile industry in Yazd and in different parts of the textile industry. Methods: This cross-sectional study was performed on 930 textile workers in Yazd. A questionnaire was used to obtain demographic information and how to use protective equipment. Then, to obtain the sound pressure level of each unit and device and to use the measurement principles, a calibrated sound level meter was used. Then the results were analyzed using SPSS Ver.29 software. Results: The participants in this study were 714 males and 216 females with a mean age of 35.27 and 33.63 years, respectively. Seven hundred fifty-six participants (81.29%) were exposed to sound pressure levels higher than 85 dB. Among the participants, only 18.39% of the people used a protective phone permanently. Except for factory E, with an average sound pressure level of 77.78 dB, the rest of the factories had an average sound pressure level higher than the occupational exposure limit. The sound measurement results of different devices show that the sound pressure levels above 90 dB are related to the parts of Dolatab, Ring, Kinetting (knitting), Chanel, Autoconer, Dolakni, Open End, MultiLakni, Tabandegi, Texture, and Poy. Conclusion: Based on the results of the present study, noise above 90 dB is considered as one of the main risk factors in most parts of the textile industry (spinning and weaving), which in the absence of engineering, managerial or individual controls on it causes hearing loss in becoming employees of this industry

scholarly journals “Horário do Soninho”: uma estratégia para reduzir os níveis de pressão sonora em uma unidade de terapia intensiva neonatal

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Adriana Duarte Rocha ◽  
Patricia Miranda Sá ◽  
Danielle Bonotto Cabral Reis ◽  
Ana Carolina Carioca Costa
Keyword(s):  
Intensive Care ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Quiet Time ◽  
Cross Sectional ◽  
Significant Difference ◽  
Sound Pressure Levels ◽  
Terapia Intensiva ◽  
Tiempo De Silencio

ResumoIntrodução: Estudos mostram que o ambiente muito estimulante, com altos níveis sonoros, interfere negativamente no desenvolvimento e crescimento de recém-nascidos. Objetivo: verificar se o "horário do soninho" é capaz de reduzir os níveis de pressão sonora em uma unidade de cuidados neonatais. Método: Trata-se de uma pesquisa transversal. A medida do nível de pressão sonora foi realizada durante 15 dias não consecutivos, com tempo de avaliação de 30 minutos antes, 1 hora durante e 30 minutos após o "horário do soninho" Resultado: Observamos uma redução dos níveis de pressão sonora durante o "horário do soninho" (p = 0,00). Essa redução permaneceu no período dos 30 minutos subsequentes, com diferença estatisticamente significante quando comparada ao período antes do "horário do soninho" (p = 0,00). Conclusão: O "horário do soninho" é uma ferramenta capaz de reduzir o nível de pressão sonora em uma unidade de terapia intensiva neonatalPalavras-Chave: ruído; Terapia Intensiva neonatal; Recém-nascido AbstractBackground: Studies show that super stimulating environment, with high sound levels, that negatively interfere in the development and growthof newborns. Aim:  Verify if the "quiet time" is able to reduce the sound pressure levels in a neonatal care unit. Method: It is a cross-sectional research. The measurement of the sound pressure level was performed during 15 non-consecutive days with an evaluation time of 30 minutes before, 1 hour during and 30 minutes after the "quiet time" Result: We observed a reduction of the sound pressure levels during the hours of quiet time (p = 0.00). This reduction remained in the period of the subsequent 30 minutes, with a statistically significant difference when compared to the period before sleep time (p = 0.00). Conclusion: The “quiet time is a tool capable of reducing sound pressure level in a neonatal intensive care unitKey Words: noise; Intensive Care, neonatal; Infant, newborn Resumen"Tiempo de silencio": una herramienta para reducir los niveles de presión acústica en una unidad de cuidados intensivos neonatalesAntecedentes: los estudios muestran que el entorno súper estimulante, con altos niveles de sonido, interfiere negativamente en el desarrollo y crecimiento de los recién nacidos. Objetivo: Verificar si el "tiempo de silencio" puede reducir los niveles de presión acústica en una unidad de cuidados neonatales. Método: es una investigación transversal. La medición del nivel de presión sonora se realizó durante 15 días no consecutivos con un tiempo de evaluación de 30 minutos antes, 1 hora durante y 30 minutos después del "tiempo de silencio" Resultado: Observamos una reducción de los niveles de presión sonora durante las horas de tiempo de silencio (p = 0.00). Esta reducción se mantuvo en el período de los siguientes 30 minutos, con una diferencia estadísticamente significativa en comparación con el período anterior al tiempo de sueño (p = 0,00). Conclusión: el “tiempo de silencio es una herramienta capaz de reducir el nivel de presión acústica en una unidad de cuidados intensivos neonatales Palabras clave: ruido; Cuidados Intensivos, neonatales; Infante, recién nacido

DETERMINATION OF MONOPOLE AND DIPOLE SOURCES OF FLOW AROUND A CYLINDER USING A VIRTUAL MICROPHONE ARRAY

Akustika ◽  
2021 ◽  
pp. 76
Author(s):  
Victor Ershov ◽  
Igor Khramtsov ◽  
Oleg Kustov
Keyword(s):  
Numerical Simulation ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Microphone Array ◽  
Pressure Level ◽  
Noise Sources ◽  
Ansys Fluent ◽  
Flow Around A Cylinder ◽  
Vortex Shedding Frequency

In this paper, the problem of localization of noise sources of flow around a cylinder was considered on the basis of a computational experiment using a virtual 54-channel microphone array. Numerical simulation was performed using the computational fluid dynamics software ANSYS Fluent. Several spatial orientations of the cylinder were considered for the generation of dipoles with different directions. Simulation of a simplified two-microphone azimuthal decomposition technique (ADT) is performed to determine the sound pressure level of the generated dipoles at a vortex shedding frequency of 1450 Hz. A procedure of localization of the noise of the flow around a virtual cylinder was performed using monopole and dipole beamforming algorithms. It was found that the numerical simulation results are in good agreement with the data obtained by other researchers, both in terms of the sound pressure level and the results of the localization of dipoles in space.

scholarly journals Determination of thermal and acoustic comfort inside a vehicle’s cabin

2018 ◽  
Vol 32 ◽  
pp. 01002
Author(s):  
Alexandra Ene ◽  
Tiberiu Catalina ◽  
Andreea Vartires
Keyword(s):  
Thermal Comfort ◽  
Air Temperature ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
The Other ◽  
Air Velocity ◽  
Acoustic Comfort ◽  
Comfort Parameters

Thermal and acoustic comfort, inside a vehicle’s cabin, are highly interconnected and can greatly influence the health of the passengers. On one hand, the H.V.A.C. system brings the interior air parameters to a comfortable value while on the other hand, it is the main source of noise. It is an intriguing task to find a balance between the two. In this paper, several types of air diffusers were used in order to optimize the ratio between thermal and acoustic interior comfort. Using complex measurements of noise and thermal comfort parameters we have determined for each type of air diffuser the sound pressure level and its impact on air temperature and air velocity.

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