Numerical examination of the impact of random terrain elevation and impedance variations on sound-field coherence

2011 ◽  
Vol 130 (4) ◽  
pp. 2437-2437
Author(s):  
D. Ketih Wilson ◽  
Santosh Parakkal ◽  
Sergey N. Vecherin ◽  
Vladimir E. Ostashev
Keyword(s):  
Sound Field ◽  
Terrain Elevation ◽  
The Impact ◽  
Field Coherence ◽  
Numerical Examination

scholarly journals In Design of an Ocean Bottom Seismometer Sensor: Minimize Vibration Experienced by Underwater Low-Frequency Noise

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3446 ◽  
Author(s):  
Xiaohan Wang ◽  
Shangchun Piao ◽  
Yahui Lei ◽  
Nansong Li
Keyword(s):  
Seismic Waves ◽  
Low Frequency ◽  
Sound Field ◽  
Average Density ◽  
Vibration Velocity ◽  
Frequency Noise ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Underwater Noise ◽  
The Impact

Ocean Bottom Seismometers (OBS) placed on the seafloor surface are utilized for measuring the ocean bottom seismic waves. The vibration of OBS excited by underwater noise on its surface may interfere with its measured results of seismic waves. In this particular study, an OBS was placed on the seabed, while ray acoustic theory was used to deduce the sound field distribution around the OBS. Then using this information, the analytical expression for the OBS vibration velocity was obtained in order to find various factors affecting its amplitude. The finite element computing software COMSOL Multiphysics® (COMSOL) was used to obtain the vibration response model of the OBS which was exposed to underwater noise. The vibration velocity for the OBS calculated by COMSOL agreed with the theoretical result. Moreover, the vibration velocity of OBS with different densities, shapes, and characters were investigated as well. An OBS with hemispherical shape, consistent average density as that of the seafloor, and a physical structure of double tank has displayed minimum amplitude of vibration velocity. The proposed COMSOL model predicted the impact of underwater noise while detecting the ocean bottom seismic waves with the OBS. In addition, it provides significant help for the design and optimization of an appropriate OBS.

Sonic Boom Propagation in Urban Canyons

2012 ◽  
Author(s):  
Kimberly A. Riegel ◽  
Victor W. Sparrow
Keyword(s):  
Large City ◽  
Sound Field ◽  
Environmental Parameters ◽  
Field Work ◽  
Sonic Boom ◽  
Sonic Booms ◽  
Sound Levels ◽  
The People ◽  
Arrival Angles ◽  
The Impact

In order to make civilian supersonic flight over land possible, the resulting sonic boom must be acceptable to the people exposed. In order to determine the impact on people, determining the behavior of a sonic boom in a large city is critical. A combined ray tracing radiosity method was developed to propagate sonic booms into urban canyons. A variety of environmental parameters were changed to determine their effect on the resulting sound field. The arrival angles of the boom, the height of the canyons, the width of the canyons, and the amount of diffusion were all varied. It was shown that the resulting sound levels from most of these parameters was highly dependent on the combination of the parameters rather than a single parameter. Diffusion was the only parameter that showed a consistent trend in the amplitude of the sound field. [Work funded by NASA and the FAA’s PARTNER Center of Excellence.]

A Robust Industrial Procedure for Measuring Modal Sound Fields in the Development of Radial Compressor Stages

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Peter Limacher ◽  
Carsten Spinder ◽  
Marius C. Banica ◽  
Heinz-Jürgen Feld
Keyword(s):  
Measurement System ◽  
Noise Source ◽  
Sound Field ◽  
Temperature Stability ◽  
Noise Emission ◽  
Radial Compressor ◽  
Sound Fields ◽  
Compressor Inlet ◽  
Time Required ◽  
The Impact

The turbocharger is a significant noise source in large diesel engines, such as those used in container vessels. Its main noise source is the radial compressor, where improvements in silencers and turbocharger insulation have led to a considerable reduction of compressor inlet noise emission over the past few years. As a result, compressor outlet noise is now becoming increasingly significant for large engines. Recently, an in-house compressor testbed was upgraded by adding an acoustic modal measurement system (MSMS) that allows detailed investigation of modal sound fields inside the piping. This forms part of an updated compressor acoustic qualification procedure. This paper is an in-depth treatise of the characteristics of this modal measurement system. The calculation approach for the modal decomposition and a simplified alternative that assumes axial propagation, as well as relevant considerations, such as spatial resolution, averaging, and the use of multiple reference sensors, are addressed. Various measurement parameters, such as repeatability, measurement time, required temperature stability, pressure scaling, flow noise and their impact on measurement uncertainty were investigated. A successful validation of the modal sound measurement system with a well-known modal sound field at the compressor inlet is also presented. Finally, the characteristics of the modal sound fields of the compressor outlet of a typical modern turbocharger are discussed. Modal decompositions at the first two blade passing frequencies (BPFs) are presented for selected operating points (OPs). The response of total sound power levels (PWLs) to compressor speed along the operating line (OL) is examined by means of both the present and the simplified algorithm. A sensitivity analysis shows the impact of volume flow and rotational speed on the modal sound distribution.

scholarly journals Estimating the influence of double-sided rounded screens on the acoustic field around a linear sound source

2021 ◽  
Vol 3 (5 (111)) ◽  
pp. 38-46
Author(s):  
Vitalii Didkovskyi ◽  
Vitaly Zaets ◽  
Svetlana Kotenko ◽  
Volodymyr Denysenko ◽  
Yuriy Didenko
Keyword(s):  
Acoustic Field ◽  
Cross Sections ◽  
Sound Source ◽  
Finite Thickness ◽  
Sound Field ◽  
Algebraic Equations ◽  
The Road ◽  
Study Results ◽  
On The Road ◽  
The Impact

This paper reports a study into the acoustic field of transport flow around noise protection screens located on both sides of the sound source. Most research on noise protection involving noise protection screens relates to the assessment of the effectiveness of screens located on one side of the noise source. The influence of the second screen on the effectiveness of the first one has been investigated only experimentally. Therefore, it is a relevant task to assess the mutual impact of the two screens between which the linear sound source is located. A problem was stated in such a way that has made it possible to derive an analytical solution and find a sound field around a linear sound source. In this case, the sound source was limited on both sides by acoustically rigid screens with finite thickness. The screens' cross-sections were shaped as part of a ring with arbitrary angles and the same radius. The problem was solved by the method of partial domains. This method has made it possible to obtain an infinite system of algebraic equations that were solved by the method of reduction. Such an approach to solving a problem allows a given solution to be applied for different cases of the mutual location of screens, source, and territory protected from noise. The study results help estimate a field between the screens, the dependence of increasing sound pressure on the road on the geometric size of the screen and the width of the road. In addition, the solution resulted in the ability to assess the impact of one screen on the efficiency of another in the frequency range of up to 1,000 Hz. It has been shown that the mutual impact of screens could reduce the screen efficiency by 2 times. The study reported here could make it possible to more accurately calculate the levels of the sound field from traffic flows when using noise protection screens, which is often performed in practice when designing new and reconstructing existing highways.

A Study on Noise in Synchronous Belt Drives: Experimental and Theoretical Analysis of Impact Sound

2000 ◽  
Author(s):  
Weiming Zhang ◽  
Tomio Koyama
Keyword(s):  
Theoretical Analysis ◽  
Natural Frequency ◽  
Sound Source ◽  
Transverse Vibration ◽  
Sound Field ◽  
Acoustic Energy ◽  
Generation Mechanism ◽  
Belt Drives ◽  
Fundamental Natural Frequency ◽  
The Impact

Abstract There are two kinds of noise in synchronous belt drives. One is steady sound caused by transverse vibration of belt, and another is impact sound radiating from meshing point of belt and pulley. Recently, it has been reported that the impact sound is due to the sound occurring in an air pipe built up between pulley groove and belt because the frequency of impact sound coincides with the fundamental natural frequency of an open ended pipe whose length equals width of the belt. However, this conclusion is obtained experimentally, there has no theoretical analysis provided. In this study, an analysis of the impact sound is provided to prove its generation mechanism and discuss factors that influence the level of sound theoretically. Sound field in an open ended pipe subjected to an impulsive sound source is analyzed. Comparison between experimental and analytical results is carried out. It is concluded that the level of impact sound is in proportion to the width of belt, and the acoustic energy of impact sound is in proportion to the cube of the width of belt.

scholarly journals Influence of Sound-Absorbing Material Placement on Room Acoustical Parameters

Acoustics ◽  
2019 ◽  
Vol 1 (3) ◽  
pp. 644-660 ◽  
Author(s):  
Jose Cucharero ◽  
Tuomas Hänninen ◽  
Tapio Lokki
Keyword(s):  
Speech Intelligibility ◽  
Sound Absorption ◽  
Sound Field ◽  
Acoustical Parameters ◽  
Open Plan ◽  
Absorbing Material ◽  
The Impact

The reverberation of a room is often controlled by installing sound absorption panels to the ceiling and on the walls. The reduced reverberation is particularly important in classrooms to maximize the speech intelligibility and in open-plan offices to make spaces more pleasant. In this study, the impact of the placement of the absorption material in a room was measured in a reverberation room and in a mockup classroom. The results show that absorption material is less efficient if it is mounted to the corners or on the edges between the walls and ceiling, if the sound field is more or less diffuse. If the room modes dominate the sound field, the most efficient location for the sound-absorbing material was found at one of the surfaces causing the modes. The results help acoustical consultants to place the absorption material in optimal locations and, generally, minimize the amount of material and save costs.

Analysis of the Present Situation of Research on Soundscape and Han-Chinese Buddhist Temples

2013 ◽  
Vol 357-360 ◽  
pp. 388-391
Author(s):  
Dong Xu Zhang ◽  
Da Ping Liu ◽  
Ze Lun Cui ◽  
Meng Xiao
Keyword(s):  
Architectural History ◽  
Sound Field ◽  
Research Direction ◽  
Han Chinese ◽  
Future Research ◽  
Historic Buildings ◽  
Acoustic Environment ◽  
Sound Environment ◽  
Solid Foundation ◽  
The Impact

In recent years the community has continued to raise awareness about the protection of historic buildings including Buddhist temples, but unfortunately the protection of the sound environment, which is an important part of the overall environment of historic buildings, is often ignored, and there is still a lack of research on the relationship between the sound environment and the traditional temples space in scholarly circles. Soundscape theory studies the sound environment from the perspective of sound, the environment and the listener, differing from traditional acoustics in considering peoples awareness and evaluation of sound in a special condition. Therefore, using soundscape theory as its major tool, it is considered to be future research direction that the impact of spatial elements in Han-Chinese Buddhist temples on the acoustic environment. By means of acoustic data to make a quantitative analysis of architectural history, it will in theory broaden the research domain of architectural history and lay a solid foundation for Chinese religious soundscape science, and in practice, will support the protection of the acoustic environment of historic buildings as intangible cultural heritage, and provide sound field parameters for the construction of a new temple.

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