Drive-noise-tolerant broadband silicon electro-optic switch

Numerical noise is an inevitable by-product of Computational Fluid Dynamics (CFD) simulations which can lead to challenges in finding optimum designs. This article draws attention to the issue, illustrating the difficulties it can cause for road vehicle aerodynamics simulations. Firstly a benchmark problem is used to assess a range of turbulence models and grid types. Large noise amplitudes up to 22% are evident for solutions computed on unstructured tetrahedral grids whereas computations on hexahedral and polyhedral grid structures exhibit substantially less noise. The Spalart Allmaras turbulence model is shown to be far less susceptible to noise levels than two other commonly-used models for this application. Secondly, multi-objective aerodynamic shape optimization is applied to a fairing for a practical road vehicle which is parameterised in terms of three design variables. Moving Least Squares (MLS) metamodels are constructed from 50 high-fidelity CFD solutions for two objective functions. Subsequent optimization is successful for the first objective, however numerical noise levels in excess of 7% give rise to difficulties for the second one. A revision to the problem leads to success and the construction of a small Pareto front. Further analysis underlines the inherent capability of MLS metamodels in dealing with noisy CFD responses.

ABSTRACTThere have been many previous noise-related studies on liquefied natural gas (LNG) facilities in the United States; however, noise control of these facilities using a top-down approach has not been explored in detail. Most studies have demonstrated noise compliance to applicable standards by focusing on a combination of treatments and specifications, with less consideration on control technology feasibility, ranking, and cost-effectiveness. The Federal Energy Regulatory Commission (FERC) prohibits natural gas facilities from emitting day-night noise levels in excess of 55 dB(A) (equivalent to 24-hr continuous level of 49 dB(A)) at nearby receivers. A case study was conducted to evaluate a top-down approach to reduce noise at a typical LNG peak-shaving facility under normal operating conditions, accounting for technical feasibility, control effectiveness, and cost implications. A modeling approach (International Organization for Standardization standard ISO 9613-2) was used to predict and evaluate the facility’s noise reduction potential. The study found that the strategy could achieve feasible and environmentally effective reductions up to 11 dB(A) at 500 m from the facility by first identifying source groups with highest-emitting sources and then targeting major noise source contributors per group. This approach is cost-effective because the FERC noise goals can still be achieved by avoiding unnecessary control costs associated with lower-ranked sources. The study identified the following four source groups as the highest noise emitters: (1) liquefaction and instrument air, (2) boil-off gas (BOG) compression, (3) glycol water system (air coolers), and (4) pretreatment. Of all the treatments evaluated, installation of enhanced silencers for gas turbine (GT) package—as well as construction of an acoustical building for the BOG compressors and drivers—resulted in the greatest noise reduction at nearby receivers. The study notes that incremental treatment costs presented in this paper are approximate estimates that may vary depending on factors such as facility size and region.Implications: This study assessed potential noise reductions associated with implementing a top–down noise control strategy on a typical LNG peak-shaving facility. The study determined the top–down noise control strategy could achieve feasible and environmentally effective reductions up to 11 decibels at receivers within 500 m from the facility’s center. As LNG suppliers need to support potential supply disruptions, some regions of the US, including New England and Gulf Coast with projected increase in LNG exports and growing needs from power sector, may find information in this study useful with regard to evaluating and prioritizing noise reduction potential of their LNG peak-shaving facilities.

Exposure to noise in recreational settings is a major public health concern. Under the Ontario Occupational Health and Safety Act, workers shall not be exposed to noise levels in excess of 85 dB over an 8-h period. It is generally accepted that the public’s exposure to noise be held to this same standard. The current pilot study explored whether the public is being exposed to excessive noise in indoor aquatic facilities across the Greater Toronto Area and, if so, at what levels. To our knowledge, no other study has explored this topic. Eight separate facilities were assessed using sound level meters to capture LAeq, LApeak, and LAS > 85 dB exceedance/duration. Public perception of noise was determined using self-administered questionnaires. LAeq ranged from 73.6 dB–82.3 dB and LApeak ranged from 102.2 dB–122 dB. Although the LAeq did not exceed the legislated standard, LApeak values were high. Noise levels were mainly associated with the type of activity in the pool and whistle blowing. Overall, the public were indifferent to the noise levels, despite the LApeak being quite high. Further studies are recommended to explore this topic, with a particular emphasis on comparison of different activities within the same facility.

AN LSI TIME SWITCH for the digital telephone switching system,which includes an 11K static RAM and 600 gates of peripheral circuits, affording performance of greater than 20MHz maximum operating frequency and 600mW power consumption, will be described. The LSI was designed for the time switch memory in the speech path of the digital telephone switching system. The low power characteristic of the LSI has made it possible to cool the system without a fan. In using general-purpose ICs, about 50 ICs are needed and the power consumption may exceed 8W to achieve the required performance. This time switch LSI realizes an equivalent lattice size of 1024 x 1024 on a single chip, quadmple of the conventional time switch LSI.

More than 40% of Koreans are exposed to excessive noise levels which can lead to serious health effects, community annoyance and sleep disturbance. Government policy and management of the noise are necessary to solve these problems. In this paper, some projects carried out to mitigate the excessive noise levels under the support of the Ministry of Environment in Korea have been introduced. They include the projects such as making a long-term plan in the field of noise management, amendment of the existing legislation and noise measurement methods, establishment of noise map directive, construction of traffic noise monitoring system, and management of low frequency noise.

We propose and numerically simulate a 2×2 Digital Optical Switch (DOS) based on silicon-on-insulator (SOI) adiabatic coupler for TE polarizations at 1550nm. The simulation results acquired by Beam-Propagation-Method (BPM) reveal that the cross-talk (CT) levels are below -27dB over a broadband of 60nm. Small simulated insertion-losses (ILs) below 0.1dB are obtained between the wavelengths 1520nm to 1580nm for both two switching states.

Tightly packaged receivers pose a challenge for noise measurements. Their only outputs are often diagnostic or benchmark information-"user data" that result from unknown processing. These include data rate test results, signal-to-noise ratio estimated by the receiver, and so on. Some of these are important gauges of communication viability that may be enshrined in performance and conformance specifications. Engineers can estimate these parameters based on standards and simplified system models, but there are few means to validate against physical measurements. We propose here a set of measurement techniques to complement and support models of system noise. The approach is founded on a semiparametric model of the noise response of a full-stack receiver. We probe this response experimentally by systematically perturbing signals and excess noise levels at the receiver input. The resulting technique is blind to protocol and implementation details. We introduce the design and implementation of some novel test capabilities required for these tests: a precision programmable excess noise source and a highly directive programmable attenuator. We also introduce a regression procedure to estimate system noise (or NF) from the controlled input conditions and summary statistics of the user data output. We also estimate uncertainty in the measurement by combining traditional methods with a Monte Carlo method that propagates random errors through the regression. Case studies demonstrate the measurement with consumer wireless networking and geolocation equipment. These include verification by repeatability testing and cross-comparison against Y-factor measurements.

Over the past several years, personal protective equipment (PPE) has been developed to protect workers from the intense radiant heat energy of an electric arc flash event. Arc flash suits including hoods and hood shield windows are offered with heat protection levels up to 100 cal/cm2. However, there is increasing concern regarding potential hazards other than heat exposure that are also part of an electric arc event, e.g. shrapnel, pressure waves and high sound levels. The NFPA 70E Technical Committee elected to limit its Hazard/Risk Category exposure levels to 40 cal/cm>sup>2 in the proposed 2004 edition until a better understanding of these additional arc flash hazards is achieved. This paper reports recent specialized testing results on hazards involving shrapnel, pressure waves and excessive noise levels. The effectiveness of current arc flash PPE against these additional arc flash hazards and the need for an alternate approach for ?rating? these additional hazards is discussed.

Almost half of the European Union (EU)’s population is exposed to road traffic noise above levels that constitute a health risk. Associations between road traffic noise and impaired sleep in adults have consistently been reported. Less is known about effects of noise on children’s sleep. The aim of this study was to examine the association between nocturnal road traffic noise exposure and children’s parental-reported sleep duration and sleep problems. The present cross-sectional study used data from The Norwegian Mother and Child Cohort Study. Parental report of children’s sleep duration and sleep problems at age 7 was linked to modelled levels of residential night-time road traffic noise. The study population included 2665 children from Oslo, Norway. No association was found between road traffic noise and sleep duration in the total study population (odds ratio (OR): 1.05, 95% confidence interval (CI): [0.94, 1.17]), but a statistically significant association was observed in girls (OR: 1.21, 95% CI: [1.04, 1.41]). For sleep problems, the associations were similar (OR: 1.36, 95% CI: [0.85, 2.16]) in girls. The ORs are presented for an increase of 10 dB. The findings suggest there is an association between road traffic noise and sleep for girls, underlining the importance of protecting children against excessive noise levels.

The excess thermal noise generated during capillary flow of polymer solutions has been studied in detail for solutions of poly(ethylene oxide) of varying concentrations in water, and for constant concentration in various solvents (mixtures of water and isopropyl alcohol). The excess noise level, which increased with flow rate, was found to be a linear function of the dimensions of the polymer coils obtained from intrinsic viscosity data. Results obtained with different solvents and concentrations show that the excess noise depends on both the concentration and the solvent system. The noise power seems to be closely connected with the entanglement density in the system, expressed as the degree of overlapping of the macromolecules, or the correlation length, i.e., the mean distance between two points of entanglement.

The current state-of-the art in noise assessment involves the development of a strategic noise map to identify areas with excessive noise levels, expressed in terms of a single time-averaged noise indicator. While noise maps yield important information regarding sound pressure levels in a particular space, they do not give any representation of the overall sound quality in that space. A more human-centered approach to noise assessment could be achieved by developing soundscapes as a complementary tool to noise mapping. However, most soundscape studies traditionally use surveys or interviews to assess general sentiment toward the acoustic environment, and as such are generally restricted to small geographic areas, compared to the entire cities considered in noise mapping. Instead of using traditional assessment techniques, this project aims to harness the potential of big data, including, for example noise complaint data or social media chatter related to noise, to better assess public sentiments towards soundscapes. This would yield an unparalleled dataset of public opinions and perceptions of the acoustic environment. Initial results based on an analysis of NYC311 complaints and geo-localized data mined from Twitter are presented.

A non-intrusive cleaning method for boiler tubes at Sasol Synfuels power station at Secunda, in the Mpumalanga province of South Africa, is preferred over conventional methods that require boiler shutdown. The elected non-intrusive cleaning method utilizes sound energy waves, produced by an acoustic horn. Due to the nature of sound propagation and the effectiveness required, there is a requisite to control and operate the sonic horn. If the acoustic horn’s sound frequency is too low, it will produce higher sound energy waves that will resonate with the plant’s harmonious frequency and cause structural damage. Conversely, if the sonic horn’s sound frequency is too high, excessive noise levels may be reached and annoy plant personnel. To prevent these undesirable outcomes posed by adopting acoustic cleaning, there needs to be a regulatory system incorporated into the configuration to mitigate vibrations and limit noise. The regulatory system comprises a control system that drives the acoustic horn’s sound frequency as intended through a set point. The designed control system meets the anticipated requirements, such that it has an ideal transient response of 0.562 s, a steady-state error achieved in 1.05 s, with 0.201% overshoot, and most importantly the closed-loop system is stable.

<b><sc>Abstract.</sc></b> Occupational health and exposure to hazards in agriculture is a major concern especially with the use of mechanized equipment. Hearing loss affects approximately 12% of the U.S. working population with 24% caused by occupational exposures. Tractors and machinery are often associated with excessive noise levels above 85 decibels however recent engineering designs of cab structures as well as tier 4 emissions complainant exhaust systems have reduced operators‘ exposures to excessive noise level. With the induction of Tier 4 engine requirements new designs have prompted a closer examination of noise exposures of cabbed and non-cabbed self-propelled equipment used in agriculture. As tractors and equipment that are utilized on farms may have limited preventive maintenance resulting in the deterioration of cab sound insulation or opening seals which may result in higher noise exposure to operators. Accessible agricultural equipment manufactured between 1978 and 2021 which were actively used on farms in Northern Utah were assessed for operator noise exposure. Following NIOSH recommended exposure limits A-weighted, 8-hour time-weighted average using a 3-dB exchange rate was collected from 29 different equipment units. The noise testing was completed after the harvest season during winter storage between December and April. Testing occurred with equipment stationary with no load. Full throttle idle engine speed averaged 2,346.9 RPMs (SD = 161.5). Average noise levels at high idle were 77.5 dBA (SD = 7.6). At high idle, non-cabbed equipment averaged 89.2 dBA (SD = 5.4). At high idle, cabbed equipment averaged 74.8 dBA (SD = 5.1). Tractors and equipment (n = 10) that were 12 years or older averaged 76.7 dBA (SD = 7.9). While this pilot project did not account for equipment loading, results from testing cabbed equipment indicate that noise levels were not significantly correlated with age of equipment (r = -.165, p = 476) however number of cab openings was significantly correlated with noise levels (r = .643, p < .001). Operators should select cab designs with fewer openings as well as follow preventive maintenance procedures to ensure integrity of seals around openings and acoustic insulation around the cab.

This chapter describes how processes of urban transformation contribute to producing new sonic/aural sensitivities. It explores the impact of the urban renewal scheme on the Mouraria's sensory environment. In the shadows of the Mouraria's revitalization, the central area of the square has been transformed into a slick outdoor multicultural food court and weekend marke. A possible side effect of the tourism-led renaissance of the Mouraria, thematizing the sound environment has been at the core of the renovation of the neighborhood's main open public space, the Praca do Martim Moniz. In June 2012 a group of residents issued a complaint to the city council about excessive noise levels in the Largo do Intendente and vicinity, a rundown area infamous for prostitution, crime and drugs located on the northern end of the Mouraria. Meanwhile, a group of local residents gathers around the benches of the Largo da Severa, a charming square located at the end of the Rua do Capelao.

&lt;p&gt;Excessive noise levels are a prevalent issue in food processing operations and, although there have been numerous studies on occupational noise, no single study has used a concurrent mixed-methods approach. Employing this study design allows for an understanding of the level of convergence (similarity) between measured noise levels and workers' attitudes and perceptions towards noise. This, in turn, allows for the identification of potential challenges with respect to the implementation of hearing conservation efforts. In this study, spot noise measurements were collected using a sound level meter. One-on-one interviews were conducted with workers to determine attitudes and perceptions towards noise in their workplaces. Subsequently, the results of the noise measurements (quantitative data) were integrated with the survey responses (qualitative data) to identify convergence. The majority of the noise measurements were found to exceed 85 dBA-the criterion mandated by the local occupational health and safety legislation. Although all study participants felt that it was noisy in the workplace, a large proportion of respondents indicated that the noise was not bothersome. With workers' perception being contradictory to the measured noise levels, it is a challenge to implement hearing conservation measures unless changes are made to raise the awareness of the risks associated with excessive noise exposure.&lt;/p&gt;