Performance of a motorway noise barrier at Heston

This paper reports on the performance and costs of a 300 m long experimental noise barrier erected alongside an elevated section of the M4 motorway to protect existing two-storey housing which is as close as 20 m to the motorway. Measured reductions in L₁₀ values, at the façades of these dwellings, were around 8 dB(A) at first floor windows and around 4 dB(A) at ground floor windows. These measured reductions were based on the levels with no barrier but with some screening due to the elevation of the road.A wooden fence in the barrier position at the start of the experiment gave reductions of about 3 dB(A) at the façades of the nearby houses. The subjective impressions of the occupants showed a markedly favourable overall reaction to the change from the wooden fence to the experimental noise barrier.A reduction in the variability of the received noise levels from the partially screened situation without a barrier to the screened situation was found. There was no significant increase in noise levels for positions on the opposite side of the motorway.     

基于新型长周期光纤光栅的掺铒光纤放大器

报道了基于高频CO₂激光脉冲写入的新型长周期光纤光栅的低噪音掺铒光纤放大器,这种新型长周期光纤光栅是用大约几千Hz的高频CO₂激光脉冲对光纤玻璃热冲击作用而形成的.在铒纤中插入一个长周期光纤光栅,会明显减少掺铒光纤放大器的放大自发辐射(ASE)噪音.报道了两种低噪音掺铒光纤放大器,作为前置放大器和线路放大器,它们的ASE噪音指数分别从4.0 dB减少到3.5 dB和从4.8 dB减少到4.3 dB,并且在作为线放时,其小信号增益从30 dB提高到37 dB,降噪及提高增益效应十分显著.     

On the prediction of impact noise,V: The noise from drop hammers

In earlier papers in this series, the concepts of “acceleration” and “ringing” noise have been studied in relation to impact machines, and values of radiation efficiency have been obtained for the various types of structural components. In the work reported in this paper the predicted and measured noise radiation from a drop hammer, both in full-scale and in $\text{1}\text{3}\text{-}\text{scale}$ model form, were examined. It is found that overall noise levels (L_eq per event) can be predicted from vibration measurements to within ± 1·5 dB, and to within ±2·5 dB in one-third octave bands. In turn this has permitted noise reduction techniques to be examined by studies of local component vibration levels rather than overall noise, a method which provides considerable enlightenment at the design stage. It is shown that on one particular drop hammer, the noise energy is shared surprisingly uniformly over four or five sources, and that when these have been reduced, the overall noise reduction is severely limited by the “acceleration” noise from the “tup” or “hammer” itself. As this is difficult to eliminate without a basic change in forging technology, it follows that “tup” enclosure or modification of the sharpness of the final “hard” impact are the only means available for any serious noise reduction. Also indicated is the reliability of using model techniques, suitably scaled in frequency and impulse magnitude, in developing machinery with impact characteristics.     

Wide-band low noise MM-wave SIS mixers with a single tuning element

Several SIS quasiparticle mixers have been designed and tested for the frequency range from 80 to 115 GHz. The sliding backshort is the only adjustable RF tuning element. The RF filter reactance is used as a fixed RF matching element. A mixer which uses a single 2×2 m² Pb-alloy junction in a quarter-height waveguide mount has a coupled conversion gain of G_M(DSB)=2.6±0.5 dB with an associated noise temperature of T_M(DSB)=16.4±1.8 K at the best DSB operation point. The receiver noise temperature T_R(DSB) is 27.5±0.8 K for the mixer test apparatus. This mixer provides a SSB receiver noise temperature below 50 K over the frequency range from 91 to 96 GHz, the minimum being T_R(SSB)=44±4 K. Another mixer with an array of five 5×5 m² junctions in series in a full-height wave-guide mount has much lower noise temperature T_M(DSB)=6.6±1.6 K, but less gain G_M(DSB)=–5.1±0.5 dB.Contribution of the U.S. Government, not subject to copyright     

The impact of urban noise on primary schools. Perceptive evaluation and objective assessment

This paper aims to assess the impact of environmental noise in the vicinity of primary schools and to analyze its influence in the workplace and in student performance through perceptions and objective evaluation. The subjective evaluation consisted of the application of questionnaires to students and teachers, and the objective assessment consisted of measuring in situ noise levels. The survey covered nine classes located in three primary schools. Statistical Package for Social Sciences was used for data processing and to draw conclusions. Additionally, the relationship of the difference between environmental and background noise levels of each classroom and students with difficulties in hearing the teacher’s voice was examined. Noise levels in front of the school, the schoolyard, and the most noise-exposed classrooms (occupied and unoccupied) were measured. Indoor noise levels were much higher than World Health Organization (WHO) recommended values: L_Aeq,30min averaged 70.5 dB(A) in occupied classrooms, and 38.6 dB(A) in unoccupied ones. Measurements of indoor and outdoor noise suggest that noise from the outside (road, schoolyard) affects the background noise level in classrooms but in varying degrees. It was concluded that the façades most exposed to road traffic noise are subjected to values higher than 55.0 dB(A), and noise levels inside the classrooms are mainly due to the schoolyard, students, and the road traffic. The difference between background (L_A95,30min) and the equivalent noise levels (L_Aeq,30min) in occupied classrooms was 19.2 dB(A), which shows that students’ activities are a significant source of classroom noise.     

Separation of differential np → pn charge-exchange cross section into flip and nonflip parts at Tn = 0.5–2.0 GeV

New results of the Delta-Sigma experiment on measuring the R _dp ratio made it possible to separate flip and nonflip parts of the differential cross section of the np → pn reaction at zero angle using the Dean formula. Phase-shift-analysis (PSA) solutions for elastic np → np scattering are transformed into a np → pn charge-exchange representation using unitary transformations, which testifies to the good agreement of the theoretical and experimental results.     

Information propagation from IP3 to target protein: A combined model for encoding and decoding of Ca signal

It is well known that information is encoded in the frequency or amplitude of Ca²⁺ signal and then decoded by target protein. However, few models considered both the encoding and decoding procedures of Ca²⁺ signal. In this work, a minimal Li-Rinzel model is coupled with a phosphorylation-dephosphorylation cycle model, which is used to investigate information transmissions from inositol 1,4,5-trisphosphate (IP₃) to target proteins and their relations. We found that the mean target protein activity increases with the IP₃ concentration, and at a low level of stimulation, the target protein can be more efficiently activated by an oscillatory signal than a constant signal of the same average calcium if Ca²⁺ acts cooperatively on the kinase. The internal noise resulting from the finite system size is also taken into account in the combined model.     

Search for the NN → 6q phase transition in the np-polarized measurements at T kin = 1–6 GeV

The measurements of np-spin observables at 0° have been performed for the first time on the Delta-Sigma experimental facility of LHE JINR up to P _n = 4.5 GeV/c using the monochromatic neutron beam. They include detailed measurements of the Δσ _L(np) spin differences and the study of the np → pn elastic charge-exchange process. In the Δσ _L(np) and −Δσ _L(I = 0) energy dependencies over the energy region T_kin = 1.2–3.7 GeV the peculiarity at 1.8 GeV was observed. Such energy behavior was predicted by the QCD approach as a signal of the NN → 6q phase transition. For the exhaustive investigation of this effect it is necessary to measure the energy dependence of the complete set of np observables with both longitudinal (L) and transverse (T) polarizations of the neutron beam and proton target. This will allow Direct Reconstruction of all three NN forward Scattering Amplitudes (DRSA) to be performed, and the observed peculiarity to be checked around T_kin = 1.8 GeV and at the higher energies using the Argand diagrams method.     

Mode selective directional couplers for overmoded waveguide systems

Two types of directional couplers for transverse electric (TE) modes are described: short and multihole couplers, respectively. They selectively pick one mode out of a mode mixture in an overmoded circular waveguide system. Unwanted modes are either statistically kept at low level or are suppressed by destructive interference in the coupling waveguide. Mode selectivity and directivity in multihole couplers oscillate up and down with an increasing number of holes, finally reaching a minimum of approximately 20 dB, unless there are competing modes with rational fractions of the beat wavelength. A multihole coupler for the TE₀₂ mode (28 GHz, 63.4 mm waveguide diameter, 41 holes) and a length of 1.6 m shows a calculated directivity of 68 dB and suppresses the unwanted modes TE₀₁ with 34 dB (24 dB), TE₂₂ with 37 dB (45 dB), and further modes TE_m (<5, m<6) with 17 dB to 34 dB in forward direction (figures in parentheses are for unwanted modes propagating in backward direction).A short directional coupler for the TE₀₁ mode (28 GHz, 63.4 mm waveguide diameter) with 16 holes and a length of 230 mm shows a directivity of 55 to 100 dB between 27.9 and 28.1 GHz, suppressing the TE₀₂ mode with 35 to 80 dB, the TE₀₃ mode with 30 to 65 dB, and the TE₂₂ mode with 30 to 70 dB.     

Separation of flip and non-flip parts of np → pn charge exchange at energies Tn = 0.5–2.0 GeV

The new Delta-Sigma experimental data on the ratio R _dp allowed separating the Flip and Non-Flip parts of the np → pn charge exchange process at the zero angle by the Dean formula. The PSA solutions for the np → np elastic scattering are transformed to the np → pn charge exchange representation using unitary transition, and good agreement is obtain.     

Community response to aircraft noise in Ho Chi Minh City and Hanoi

To formulate Vietnamese and global noise policies, social surveys on community response to aircraft noise and combined noise from aircraft and road traffic were carried out in Ho Chi Minh City from August to September 2008 and in Hanoi from August to September 2009. In total, 1562 and 1397 responses were obtained in Ho Chi Minh City and Hanoi, respectively. The aircraft noise was measured for seven successive days, and the combined noise was measured for 24 h. Aircraft and combined noise exposures ranged from 53 to 71 dB and 73 to 83 dB L_den in Ho Chi Minh City and from 48 to 61 dB and 70 to 82 dB L_den in Hanoi, respectively. The dose–response curve for aircraft noise for Vietnam was established and fitted onto the curve for the European Union. For the same noise exposure, the aircraft noise annoyance in Hanoi was higher than that in Ho Chi Minh City because of the lower background noise level in Hanoi.     

Laboratory annoyance and different traffic noise sources

The acute annoyance reaction to different noise sources (lorries, aircraft, mopeds and trains) was investigated in a laboratory experiment. Students were exposed to different noise climates at noise levels 70 and 80 dB(A) for 25 minutes, and their reactions were subsequently assessed by using a questionnaire. Their general sensitivity to noise was also evaluated. The results demonstrated that L_eq gave the best correlation with annoyance. However, lorry noise was found to be less disturbing than aircraft noise at the same L_eq value. This was more pronounced if the different noises were compared at equal peak dB(A) levels. The results suggest that other factors such as the irregularity of the noise or the individual experience of the noise are of importance for the annoyance reaction. A relationship was found between the general annoyance score and annoyance reactions in the laboratory. Questionnaires could thus be a suitable tool for identifying noise sensitive persons.     

Investigation of the dose-response relationship for road traffic noise in Assiut, Egypt

A field study has been carried out in urban Assiut city, Egypt. The goals of this study are: (1) to carry out measurements to evaluate road traffic noise levels, (2) to determine if these levels exceeds permissible levels, (3) to examine people’s attitudes towards road traffic noise, (4) to ascertain the relationship between road traffic noise levels and degree of annoyance. The measurements indicate that traffic noise noise levels are higher than those set by Egyptian noise standards and policy to protect public health and welfare in residential areas: equivalent continuous A - weighted sound pressure levels (L_A eq) = 80 dB and higher were recorded, while maximum permissible level is 65 dB. There is a strong relationship between road traffic noise levels and percentage of highly annoyed respondents. Higher road traffic noise levels mean that the percentage of respondents who feel highly annoyed is also increased.     

轻卡进气管的结构优化及其声学性能

为有效降低轻卡进气管的噪声，首先通过原始进气管的噪声实验，测试得出噪声的主要贡献频率，结合管道的布置情况，进行了消声器(谐振腔)的设计，进而完成对进气管的优化设计；通过专业声学分析软件LMS Virtual.lab对优化前后的进气管进行声学性能的模拟研究，得出了谐振腔对声场的具体影响；通过噪声实验，分析出加装谐振腔的进气管相比于原始进气管的降噪效果。研究结果表明：在所研究的进气管噪声的主要贡献频率下(即125 Hz、180 Hz、465 Hz、640 Hz)，加装谐振腔后，传递损失均能得到有效增加；在怠速工况和加速工况下，优化后的进气管噪声值均能满足限定值。因此，通过添加谐振腔来优化进气管可以达到了较好的降噪效果。该研究可为汽车进气管降噪元件的优化设计提供一定的指导。     

Appraisal of Urban Road Traffic Noise in tier-II City (Surat City), India

Urban road traffic noise pollution has always been identified as a severe problem that affects urban populants. In developing nation, road traffic noise pollution depends on the composition of heterogeneous traffic composition. These traffic compositions contain vehicles, which have different sizes, speeds variations, a different dimension of vehicles. Environmental noise measurements have been carried out during day-time and night-time in different locations of tier-II city of India. The noise levels have been continuously measured over 24 h periods using kimo DB 300 class-2 noise level meter. The data contained in this research paper represent 768 measurement hours. All the information has been used to investigate the time patterns of the noise levels under a wide range of different conditions and to study the relationships between noise levels and traffic in urban areas. Maximum L_Aeq was observed 73.3 dB(A) at B₁₄ location and the minimum was recorded 65.7 dB(A) at C₃ location, which was greater than the central pollution control board (CPCB) prescribed limits during night time. A major reason for the generation of road traffic noise is due to the equal composition of 2-wheeler and 4-wheeler on the arterial road and heavy vehicles were recorded during morning peak and evening peak even though they are prohibited during peak hours.     

The neutron-proton scattering length in the reaction9Be(p,np)8Be at 7.5 MeV

The relative differential cross section of the⁹Be(p, np)⁸Be _gs reaction at 7.5 MeV has been measured in an FSI geometry. A strongn-p FSI peak was observed with virtually no sequential decay modes interfering. The Watson-Migdal analysis of this peak yields the scattering lengtha _np =–23.8_–1.2 ^–1.1 fm with the effective ranger _np =2.76 fm.     

Performance analysis of wavelength conversion using a light-injected laser diode based on improved rate equations

The extinction and signal to noise ratios, the two main figures-of-merit for a wavelength converted signal are analyzed on the basis of the improved rate equations. The model accurately considers the mutual coupling parameter β_m which indicates the efficiency of the wavelength conversion. A simple relationship among extinction ratio, signal to noise ratio and the mutual coupling parameter β_m is given. With the simulation results, we find that the high extinction and signal to noise ratios depends on higher pump (i.e. original) power, optimum probe (i.e. converted) power and less wavelength spacing between them, which is in accordance with the analysis of mutual coupling parameter β_m.