Investigation and Optimization of a Spare Wheel Well to Reduce Vehicle Interior Noise

2003 ◽  
Vol 11 (03) ◽  
pp. 425-449 ◽  
Author(s):  
Steffen Marburg ◽  
Hans-Jürgen Hardtke
Keyword(s):  
Transfer Function ◽  
Sound Pressure Level ◽  
Structural Component ◽  
Sound Pressure ◽  
Pressure Level ◽  
Frequency Range ◽  
Noise Emission ◽  
Noise Transfer Function ◽  
Contribution Analysis ◽  
Design Variables

Optimization of structures with the intention to reduce noise emission has become an efficient tool during the past decade. Various approaches and applications have been published and will be briefly reviewed in this paper. Then, the structural component model of a spare wheel well and the fluid model of a sedan cabin are described. The noise transfer function is defined as the sound pressure level in vicinity of the driver's ear due to a harmonic force excitation at engine supports. The frequency range of 0–100 Hz is considered. In a first investigation, it is tested whether stiffening of the entire structural component really decreases the noise transfer function. It can be seen that this stiffening mainly affects noise emission in the upper frequency range. In a contribution analysis, i.e. analysis of the surface contribution to the noise at the driver's ear, the original model and the stiffened model are compared. This contribution analysis includes frequency ranges by summation of contribution and/or contribution levels. Modification of the structure by design variables consists of modification of the shell geometry, i.e. curvature. Two regions are selected at the bottom of the wheel well. Optimization of 30 design variables leads to a gain of 1.15 dB in the objective function being the root mean square value of the sound pressure level at the driver's ear. Finally, we discuss the results. In most papers on structural acoustic optimization, higher decreases have been reported. An explanation is provided, why this was not possible for the structure that has been investigated here. The new shape, however, seems to be a reasonable choice.

scholarly journals Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in the 10–40 kHz frequency range

2020 ◽  
Vol 18 (2) ◽  
pp. 1451-1463
Author(s):  
Witold Mikulski
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sheet Steel ◽  
Pressure Level ◽  
Sound Insulation ◽  
Frequency Range ◽  
Noise Sources ◽  
Human Environment ◽  
Absorbing Material ◽  
Acoustic Enclosures

Abstract Purpose The purpose of the research is to work out a method for determining the sound insulation of acoustic enclosures for industrial sources emitting noise in the frequency range of 10–40 kHz and apply the method to measure the sound insulation of acoustic enclosures build of different materials. Methods The method is developed by appropriate adaptation of techniques applicable currently for sound frequencies of up to 10 kHz. The sound insulation of example enclosures is determined with the use of this newly developed method. Results The research results indicate that enclosures (made of polycarbonate, plexiglass, sheet aluminium, sheet steel, plywood, and composite materials) enable reducing the sound pressure level in the environment for the frequency of 10 kHz by 19–25 dB with the reduction increasing to 40–48 dB for the frequency of 40 Hz. The sound insulation of acoustic enclosures with a sound-absorbing material inside reaches about 38 dB for the frequency of 10 kHz and about 63 dB for the frequency of 40 kHz. Conclusion Some pieces of equipment installed in the work environment are sources of noise emitted in the 10–40 kHz frequency range with the intensity which can be high enough to be harmful to humans. The most effective technical reduction of the associated risks are acoustic enclosures for such noise sources. The sound pressure level reduction obtained after provision of an enclosure depends on its design (shape, size, material, and thickness of walls) and the noise source frequency spectrum. Realistically available noise reduction values may exceed 60 dB.

Topology Optimization of Gearbox to Reduce Radiated Noise

2015 ◽  
Author(s):  
J. P. Wang ◽  
G. Liu ◽  
S. Chang ◽  
L. Y. Wu
Keyword(s):  
Topology Optimization ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Dynamic Loads ◽  
Field Point ◽  
Radiated Noise ◽  
Contribution Analysis ◽  
Acoustic Contribution ◽  
Mode Order

In this paper, topology optimization of gearbox to reduce the radiated noise is studied based on the analysis of modal acoustic contribution and panel acoustic contribution. Firstly, the bearing dynamic loads are obtained by solving the dynamic equations of gear system. Secondly, the vibration of gearbox is calculated using FEM and the radiated noise is simulated using BEM by taking these bearing dynamic loads as excitations. Thirdly, the panel having larger contribution to the sound pressure level (SPL) at a specific field point is found by panel acoustic contribution analysis (PACA), and this panel is taken as design domain. The mode order with larger contribution is determined by modal acoustic contribution analysis (MACA), and making corresponding natural frequency becomes far away from excited frequency is taken as a constraint. Finally, the topology optimization of gearbox is completed using SIMP method, and the ribs are arranged according to the optimization results. The results show that the equivalent sound pressure level at objective field point can be reduced obviously by using this method.

scholarly journals Noise-silencing technology for upright venting pipe jet noise

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879481 ◽  
Author(s):  
Enbin Liu ◽  
Shanbi Peng ◽  
Tiaowei Yang
Keyword(s):  
Natural Gas ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Low Frequency ◽  
Jet Noise ◽  
Pressure Level ◽  
Living Environment ◽  
Frequency Noise ◽  
Frequency Range ◽  
Expansion Chamber

When a natural gas transmission and distribution station performs a planned or emergency venting operation, the jet noise produced by the natural gas venting pipe can have an intensity as high as 110 dB, thereby severely affecting the production and living environment. Jet noise produced by venting pipes is a type of aerodynamic noise. This study investigates the mechanism that produces the jet noise and the radiative characteristics of jet noise using a computational fluid dynamics method that combines large eddy simulation with the Ffowcs Williams–Hawkings acoustic analogy theory. The analysis results show that the sound pressure level of jet noise is relatively high, with a maximum level of 115 dB in the low-frequency range (0–1000 Hz), and the sound pressure level is approximately the average level in the frequency range of 1000–4000 Hz. In addition, the maximum and average sound pressure levels of the noise at the same monitoring point both slightly decrease, and the frequency of the occurrence of a maximum sound pressure level decreases as the Mach number at the outlet of the venting pipe increases. An increase in the flow rate can result in a shift from low-frequency to high-frequency noise. Subsequently, this study includes a design of an expansion-chamber muffler that reduces the jet noise produced by venting pipes and an analysis of its effectiveness in reducing noise. The results show that the expansion-chamber muffler designed in this study can effectively reduce jet noise by 10–40 dB and, thus, achieve effective noise prevention and control.

OPTIMAL DESIGN OF A 1-3 PIEZOCOMPOSITE TONPILZ TRANSDUCER BY MEANS OF THE FINITE ELEMENT METHOD

2008 ◽  
Vol 22 (11) ◽  
pp. 1087-1092 ◽  
Author(s):  
DA LIE PEI ◽  
YONGRAE ROH
Keyword(s):  
Finite Element Method ◽  
Sound Pressure ◽  
Optimization Technique ◽  
Pressure Level ◽  
Frequency Bandwidth ◽  
The Finite Element Method ◽  
Frequency Range ◽  
Design Variables ◽  
Structural Variables ◽  
Functional Forms

Underwater Tonpilz transducer is designed with 1-3 piezocomposite materials to overcome the problems with conventional piezoceramic transducers. With the FEM, the variation of the resonance frequency, bandwidth and sound pressure of the transducer are analyzed in relation to the structural variables of the transducer. Through statistical multiple regression analysis of the results, functional forms of the transducer performance are derived in terms of design variables. By applying the constrained optimization technique, SQP-PD, to the derived functions, the optimal structure of the transducer is determined that can provide the highest sound pressure level at a given resonant frequency over a pre-determined frequency range. The validity of the optimized results is confirmed through comparison of the optimal performance with that of the FEA.

Vibration and Noise Damping Treatment for an Excavator Cab

2014 ◽  
Vol 889-890 ◽  
pp. 455-458
Author(s):  
Yong Zhen Mi ◽  
Yi Qi Zhou ◽  
Li Wang
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Pressure Level ◽  
Material Layer ◽  
Contribution Analysis ◽  
Damping Material ◽  
Great Decline ◽  
Chlorobutyl Rubber ◽  
Acceleration Signals

Acceleration signals at the mounts of an excavator cab are collected and analyzed, on the basis of which causes of peak values in the sound pressure level (SPL) at the drivers right ear (DRE) are discussed. A damping material layer made up of chlorobutyl rubber is arranged to the cabs panels by simulations according to results of panel acoustical contribution analysis, which indicates a great decline of the SPL peak values.

Effects of blade surface roughness on compressor performance and tonal noise emission in a marine diesel engine turbocharger

2020 ◽  
Vol 234 (14) ◽  
pp. 3476-3490
Author(s):  
Chen Liu ◽  
Yipeng Cao ◽  
Sihui Ding ◽  
Wenping Zhang ◽  
Yuhang Cai ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Sound Pressure Level ◽  
Total Pressure ◽  
Sound Pressure ◽  
Leading Edge ◽  
Pressure Level ◽  
Blade Surface ◽  
Noise Emission ◽  
Tonal Noise ◽  
Compressor Performance

A numerical study was conducted to investigate the effects of blade surface roughness on compressor performance and tonal noise emission. The equivalent sand-grain roughness model was used to account for blade surface roughness, and a hybrid method that combines computational fluid dynamics and boundary element method was used to predict compressor performance and tonal noise. The numerical approach was validated against experimental data for a baseline compressor. Nine different cases with different blade surface roughness were studied in this paper, the global performance was analyzed under compressor design speed, and the tonal noise level was predicted under the design condition. The results indicate that compressor total-to-total pressure ratio and isentropic efficiency were gradually decreased with the increasing blade surface roughness. Besides, the blade total pressure loss coefficient and the efficiency loss coefficient were also increased. It was found that the reverse flow at the leading edge of compressor rotor blades reduced blade loading. The pressure fluctuation at the leading edge showed that the peak of pressure fluctuations increased as the blade surface roughness was increased. The sound pressure level at blade-passing frequency shows a significant change with variation in blade surface roughness, which results in an increased total noise level. Furthermore, it was shown that the blade surface roughness had nearly no influence on acoustic directivity, but the sound pressure level increased with the increase in roughness, especially at blade-passing frequency.

Research Papers: Music-Induced Vibrations in a Concert Hall and a Church

2013 ◽  
Vol 38 (1) ◽  
pp. 13-18 ◽  
Author(s):  
Sebastian Merchel ◽  
Mehmet Ercan Altinsoy
Keyword(s):  
Transfer Function ◽  
Sound Pressure ◽  
Pressure Level ◽  
The Body ◽  
Frequency Range ◽  
Research Papers ◽  
Concert Hall ◽  
Acceleration Level ◽  
Sensory Modalities ◽  
Opera House

Abstract Sound and vibrations are often perceived via the auditory and tactile senses simultaneously, e.g., in a car or train. During a rock concert, the body vibrates with the rhythm of the music. Even in a concert hall or a church, sound can excite vibrations in the ground or seats. These vibrations might not be perceived separately because they integrate with the other sensory modalities into one multi-modal perception. This paper discusses the relation between sound and vibration for frequencies up to 1 kHz in an opera house and a church. Therefore, the transfer function between sound pressure and acceleration was measured at different exemplary listening positions. A dodecahedron loudspeaker on the stage was used as a sound source. Accelerometers on the ground, seat and arm rest measured the resulting vibrations. It was found that vibrations were excited over a broad frequency range via airborne sound. The transfer function was measured using various sound pressure levels. Thereby, no dependence on level was found. The acceleration level at the seat corresponds approximately to the sound pressure level and is independent of the receiver position. Stronger differences were measured for vibrations on the ground.

Test and Analysis of Noise Reduction Effect for Different Heights and Distances of Sound Barrier

2011 ◽  
Vol 243-249 ◽  
pp. 4447-4450 ◽  
Author(s):  
Yan Liu ◽  
Bing Yang ◽  
Xiao Pai Zhang ◽  
Zhi Fang Zhong ◽  
Hua Xin Dong ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Sound Pressure Level ◽  
High Frequency ◽  
Sound Pressure ◽  
Pressure Level ◽  
High Frequency Range ◽  
Frequency Range ◽  
Sound Barrier ◽  
Test Points ◽  
Reduction Effect

Based on the comparative analysis on the low-noise road surface, noise reduction green belts, noise barriers and other noise reduction methods, the sound barrier is put forward as an important method for reducing the city road traffic noise. The noise reduction effects for different heights and different distances of the sound barrier are tested and analyzed through noise and vibration test and analysis system, the following conclusions can be drawn. At the same heights from the ground, the father the test points away from the noise barrier, the higher the sound pressure level will be; At the same distances from the sound barrier, the nearer the test points from the ground, the smaller the sound pressure level will be; All of the sound pressure level curves have basically the same variation trend and the main noise frequency band is from 160 to 1600Hz; In the high frequency range which is greater than 1600Hz, the sound pressure level decrease significantly, indicating that the sound barrier has better noise reduction effect for high frequency range. The results provide the basis for the design of the sound barriers.

scholarly journals Near-Direct and Far-Reverberant Field Response of Direct Radiator Loudspeakers

2019 ◽  
Vol 9 (1) ◽  
pp. 2821-2826
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Full Range ◽  
Sound Quality ◽  
Pressure Level ◽  
Frequency Range ◽  
Response Characteristics ◽  
Response Data ◽  
Field Response ◽  
Reverberant Field

Typical audience seating arrangements in rooms and auditoria warrant reinvestigation of the direct radiator speaker response in the near-direct and far-reverberant fields, as the response data provided by the manufacturer is always ideal and does not account for the effect of those fields. The speaker response characteristics of a variety of direct radiator loudspeakers ranging from the conventional squawker to the full range radiator have been investigated in these fields. The speaker response is investigated in the 50 -10 kHz frequency range, by measuring the A-weighted SPL (sound pressure level) in the near-direct and far-reverberant fields, using an acoustic analyzer. The field-specific characteristic for each of the radiators is determined by fitting the SPL data obtained to an appropriate polynomial. The coefficients obtained thereby, allow an objective field-specific study amongst radiators. When a set of direct radiator loudspeakers is available, it is necessary to configure their application, depending upon the optimum sound quality required for a given enclosure, in near-direct field and far-reverberant field. The outcome of this work assists one to configure the best radiator ensemble for a given enclosure, despite placement constraints.

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