縮尺模型試験による継目部衝撃音の評価

Railway noise from conventional meter-gauge lines in Japan mainly consists of rolling noise and traction-motor fan noise. Rolling noise is generated by vertical vibration of the wheel and rail, which is induced by relative displacement between the two due to the roughness on their surfaces. Through field tests, it was found that the excitation of rolling noise is determined by both the wheel/rail roughness and the vibratory behaviour of rolling stock and tracks. A theoretical model for rolling noise (such as TWINS) was then applied to Japanese railways, with the predictions showing a close correlation to the measured values. In terms of noise spectra, the rail was found to contribute more to rolling noise than the wheel in much of the frequency range. An attempt to estimate the effect of wheel and track parameters on rolling noise was also made using the TWINS model. The stiffness of the rail pad was found to affect the balance between the rail and sleeper components of noise, and additional damping for the rail was deemed effective in reducing the rail component of noise.

Wheel/rail noise—Part III: Impact noise generation by wheel and rail discontinuities

Noise complaints among neighbors in apartment building are mainly caused by floor impact noise that is structure born noise due to occupant induced floor vibration. To control this noise problems many researchers have investigated floor systems and finishing materials. Light-weight impact noise affects by finishing materials, but heavy-weight impact noise induced by heel impacts during normal walking or jumping of children is concerned with structural system and floor vibration. To figure out the characteristics of floor impact noise and transmission of floor vibration due to human activities, vibration tests were conducted in apartment buildings. Impact hammer, heel drop and walking activities were loaded at center of upstairs living room, and accelerations of slabs for both upstairs and downstairs and sound pressure levels for downstairs were measured. The acceleration ratio of transmitted floor vibration to downstairs and human induced vibration in upstairs was between 0.5 and 1.0 according to slab size, wall, and load type. And floor impact noise occurred in the range of natural frequency of slab.

This study aims to address a key challenge in geosynthetic engineering by ensuring that scaled geocells are produced and utilized in accordance with dimensional analysis principles and similarity laws, thereby accurately replicating the behavior of prototype geocells. Utilizing a commercially available 3D printer, model geocells were fabricated to closely represent the geometric and material properties of prototype high-density polyethylene geocells. A comprehensive examination was conducted on the tensile strength/modulus of 3D-printed geocells using different filaments and infill rates. The findings revealed that geocells printed with thermoplastic polyurethane filaments, particularly with a 5% infill rate, closely resembled the prototype geocells in terms of the tensile modulus at specific elongation levels, showcasing a promising avenue for 1:3 scaled model tests. The successful creation of geocell layers using the elastic filaments was achieved through careful calibration of printing settings, including first-layer precision, bed leveling, and controlled printing speed. The effects of scaling on strip footings reinforced by both HDPE-fabricated and 3D-printed geocells were also evaluated in small-scale laboratory tests, focusing on their pressure-settlement response and improvement factors. Utilizing 3D-printed geocell layers in model tests addresses the challenge of employing unscaled prototype geocells.

With continued growth in air travel, sensitivity to community noise intensifies and materializes in the form of increased monitoring, regulations, and restrictions. Accordingly, realization of quieter aircraft is imperative, albeit only achievable with reduction of both engine and airframe components of total aircraft noise. Model-scale airframe noise testing has aided in this pursuit; however, the results are somewhat limited due to lack of fidelity of model hardware, particularly in simulating full-scale landing gear. Moreover, simulation of true in-flight conditions is non-trivial if not infeasible. This paper reports on an investigation of full-scale landing gear noise measured as part of the 2005 Quiet Technology Demonstrator 2 (QTD2) flight test program. Conventional Boeing 777-300ER main landing gear were tested, along with two noise reduction concepts, namely a toboggan fairing and gear alignment with the local flow, both of which were down-selected from various other noise reduction devices evaluated in model-scale testing at Virginia Tech. The full-scale toboggan fairings were designed by Goodrich Aerostructures as add-on devices allowing for complete retraction of the main gear. The baseline-conventional gear, faired gear, and aligned gear were all evaluated with the high-lift system in the retracted position and deployed at various flap settings, all at engine idle power setting. Measurements were taken with flyover community noise microphones and a large aperture acoustic phased array, yielding far-field spectra, and localized sources (beamform maps). The results were utilized to evaluate qualitatively and quantitatively the merit of each noise reduction concept. Complete similarity between model-scale and full-scale noise reduction levels was not found and requires further investigation. Far-field spectra exhibited no noise reduction for both concepts across all angles and frequencies. Phased array beamform maps show inconclusive evidence of noise reduction at selective frequencies (1500 to 3000 Hz) but are otherwise in general agreement with the far-field spectra results (within measurement uncertainty).

One of the main factors affecting the durability of bridge structures is the presence of expansion joints at bridge support locations. The inability of current joint systems to provide reliable, long-term, leak-proof performance generally leads to early leakage of chloride-contaminated water through these joints, thereby causing premature corrosion in the deck elements below. This problem is particularly evident in older-type multispan bridges in which the girders are simply supported at the piers and are separated by expansion joints or simple paved-over joints. To address this problem, the Ministry of Transportation of Ontario (MTO) has recently rehabilitated a number of bridge decks using a debonded link slab system to replace the deck joints at the pier locations. To get a better understanding of the performance and reliability of this new rehabilitative technique, MTO recently carried out an experimental research study of the long-term performance of the system on scale test models that were subjected to extensive cyclic loading in the laboratory. At the same time, it carried out a load test of a recently rehabilitated structure to study its structural behavior both before and after the link slab was constructed. The test structure was instrumented with sensors that measured deflections and strains in the link slab and girders. This paper describes the experimental research study and the behavioral load tests that were carried out, and discusses the results obtained. The experimental study showed that the long-term performance of the link slab was not affected by the extensive cyclic loading to which the model was subjected, whereas the load testing of the test structure showed that it satisfied the serviceability limit state requirements of the Canadian Highway Bridge Design Code, thus validating the design methodology of the system.

Noise caused by transportation significantly exceeds the 55 dBA. The purpose of this study was to determine the level of transportation traffic noise at the Merauke city crossing and its solutions. Noise caused The lack of proper attention to the impact of noise from traffic flow at a crossroads. The Development of additional techniques for noise reduction in this area is needed. The results obtained are very important for areas with solutions at every highway intersection The results obtained are very important knowing the noise above the standard value at every highway intersection. This research develops techniques to reduce transportation traffic noise at the crossroads of Merauke city which are applied in design practice. Experimental studies in real conditions in the characteristic areas of Merauke City using sound level meter measurements. This research was carried out experimentally by taking measurements at each crossroads and theoretical solving methods. The good convergence results confirm the impact of noise on the immediate area with a slightly higher crossing than the value on a normal two-lane road. The proposed solution will allow providing additional protection against transportation noise.

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In the present paper, characteristics of rail vibration and radiated sound power from concrete slab tracks for domestic high speed train(KTX) is investigated by means of a numerical method. The waveguide finite element and boundary element are combined and applied for this analysis. The concrete slab track is modelled simply with a rail and rail pad regarding the concrete slab as a rigid ground. The wave types which contribute significantly to the rail vibration and radiated noise are identified in terms of the mobility and decay rates. In addition, the effect of the rail pad stiffness on the radiated power is examined for two different rail pad stiffnesses.

Faced with the constant development in construction resources and techniques, there is a need to know the materials used since they directly interfere with the acoustic performance of buildings. Moreover, residential buildings are products to be marketed in which builders seek to reduce costs and optimize the application of their economic resources in attributes valued by the target audience, and noise reduction is one of these items. Therefore, to promote the use of elements with adequate acoustic behavior to prioritize the acoustic comfort of users and to encourage the use of materials that contribute to this end, the objective of this paper is to analyze the financial viability between the square meter of construction and the acoustic behavior of different flooring systems. The methodology used impact sound insulation data determined in field tests, obtained through laboratory tests, and the cost analysis was done with commercial software. The results showed the importance of implementing floating floor construction systems to achieve good acoustic performance. Furthermore, it was observed that in several cases, the additional cost with the floating floor application becomes insignificant when diluted in a multi-unit building, given the increase in the final sale value of an apartment with optimized performance (minimum/superior). Keywords: Building performance. Technology in buildings. Impact noise

A method has been developed to determine the aerodynamic noise from the bogie of a high-speed train using a two-dimensional microphone array in a wind tunnel. First, the flow velocity under the train car in the rail direction was measured in a field test. Second, the flow distribution was simulated in the wind tunnel. Third, aerodynamic noise generated by a bogie was estimated from the source distribution measured using a two-dimensional microphone array. Finally, the noise generated from the lower part of the car, which was obtained by adding the aerodynamic noise and the rolling noise estimated by the TWINS model, was compared with the result obtained from the field test. It was found that the estimated noise shows good agreement with the measurement obtained in the field test. The estimated lower part noise levels were consistent with the actual experimental measurements. This conclusion suggests that this method is appropriate to estimate aerodynamic bogie noise quantitatively. It is also shown that below 500 Hz the contribution of the aerodynamic bogie noise is more than those of the rolling and machinery noise.

Work was conducted on a curved track section of 350 m radius on an underground line where excessive in-car noise was experienced by passengers. Vulcanized bonded baseplates were installed on the section. Investigation was performed comprising initial in-car noise and carriage floor vibration level assessments, testing of rail surface roughness, rail vertical and lateral vibration responses during train normal operation, and measurements of track decay rate. A rail web damper designed for in-car noise control was evaluated on a trial section of track. All experimental data were analysed, showing that the highest LAmax was about 95 dB and the highest LAeq 91 dB for the Egg Fasteners Section. 1/3 octave band peak frequencies of dominant in-car noise is at 250 Hz and 315 Hz, consistent with those of rail roughness and rail vibration spectrum. Reduction of rail vibration velocity is not obvious in these frequency bands on the track with rail web damper installed.

Reduction of noise nuisance from footsteps on stairs

Army Moves to Higher Level of Hearing Protection

This study is a basic research on improving floor finishing materials technology to reduce floor impact noise in apartments. The floor impact noise reduction performance and impact force of floor mats were measured on a general standard floor structure in Korea (concrete slab 210 mm + EPS 30 mm + finishing mortar 50 mm). Six types of PE mats, three types of EVA mats, and three types of PU mats were targeted. Lightweight and heavyweight impact noise were measured and evaluated according to KS F ISO 16283-2 and KS F ISO 717-2, and the floor impact noise reduction value of the mat was evaluated by the difference in the level of impact noise according to the installation of the mat. In addition, the impact force of the mats was measured according to JIS A 6519. The reduction performance of lightweight impact noise was high in the order of PU, PE, and EVA. PE mats showed a reduction performance of up to 4 dB in heavyweight impact noise. In addition, the impact force of the PE mats was the smallest, and the impact force decreased as the thickness of the mat increased.

This paper proposes a noise reduction method for reducing impact noise. The proposed method is based on a zero phase (ZP) signal which is defined as the IDFT of a spectral amplitude. The ZP signal of the impact noise has zero values except of around the origin, since its spectral amplitude is almost flat. When a speech signal has periodicity, its ZP signal has also periodicity. Hence, when the speech signal mixed with the impact noise, the noise can be reduced by replacing samples around the origin with samples around the second period of the ZP signal. A practical impact noise often has damped oscillation which is similar to a periodic signal. Under the assumption that the pitch of the damped oscillation is higher than one of speech, we detect and reduce the damped oscillation by introducing an additional pitch estimator into the ZP replacement method.