Noise Simulation Technique Research Articles

Interactive simulation of aircraft noise in aural and visual virtual environments

This paper describes a novel aircraft noise simulation technique developed at RWTH Aachen University, which makes use of aircraft noise auralization and 3D visualization to make aircraft noise both heard and seen in immersive Virtual Reality (VR) environments. This technique is intended to be used to increase the residents’ acceptance of aircraft noise by presenting noise changes in a more directly relatable form, and also aid in understanding what contributes to the residents’ subjective annoyance via psychoacoustic surveys. This paper describes the technique as well as some of its initial applications. The reasoning behind the development of such a technique is that the issue of aircraft noise experienced by residents in airport vicinities is one of subjective annoyance. Any efforts at noise abatement have been conventionally presented to residents in terms of noise level reductions in conventional metrics such as A-weighted level or equivalent sound level Leq. This conventional approach however proves insufficient in increasing aircraft noise acceptance due to two main reasons – firstly, the residents have only a rudimentary understanding of changes in decibel and secondly, the conventional metrics do not fully capture what the residents actually find annoying i.e. characteristics of aircraft noise they find least acceptable. In order to allow least resistance to air-traffic expansion, the acceptance of aircraft noise has to be increased, for which such a new approach to noise assessment is required.

Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant

On-road, a vehicle experiences unsteady flow conditions due to turbulence in the natural wind, moving through the unsteady wakes of other road vehicles and travelling through the stationary wakes generated by roadside obstacles. Separated flow structures in the sideglass region of a vehicle are particularly sensitive to unsteadiness in the onset flow. These regions are also areas where strong aeroacoustic effects can exist, in a region close to the passengers of a vehicle. The resulting aeroacoustic response to unsteadiness can lead to fluctuations and modulation at frequencies that a passenger is particularly sensitive towards. Results presented by this paper combine on-road measurement campaigns using instrumented vehicles in a range of different wind environments and aeroacoustic wind tunnel tests. A new cabin noise simulation technique was developed to predict the time-varying wind noise in a vehicle using the cabin noise measured in the steady environment of the wind tunnel, and a record of the unsteady onset conditions on the road, considering each third-octave band individually. The simulated cabin noise predicted using this quasi-steady technique was compared against direct on-road cabin noise measurements recorded under the same flow conditions to assess the response of the vehicle to oncoming flow unsteadiness. The technique predicted the modulation of the wind noise under unsteady on-road conditions with good fidelity. This is because the cabin noise response to oncoming flow unsteadiness remained generally quasi-steady up to fluctuation frequencies of approximately 2 to 5 Hz, with fluctuations at higher scales having a progressively smaller impact, and because most of the onset flow fluctuation energy on the road occurs at frequencies below this threshold. The relative impact of the baseline level of cabin noise and the sensitivity of the cabin noise to changes in yaw angle were assessed in terms of occupant perception and this highlighted the importance of modulation. This can provide guidance when assessing the on-road wind noise performance of vehicle geometry modifications and of different vehicles.

Review of a simple noise simulation technique in digital radiography

Reduction of exposure dose and improvement in image quality can be expected to result from advances in the performance of imaging detectors. A number of researchers have reported on methods for simulating reduced dose images. The simplest method provides reduced dose images by adding white Gaussian noise with a certain standard deviation to the original image. Our aim in this study was to develop and validate a system with a graphic user interface for simulating reduced dose images by a simple method. Here, we describe a technical approach with the use of a flat-panel detector system, and we validated the simulation performance in reducing the dose objectively and subjectively. In addition, the technical limitations and possible solutions to the simple method are suggested based on the validation results presented in this paper.

Simulation and Analysis of Random Decision Errors in Clocked Comparators

Clocked comparators have found widespread use in noise sensitive applications including analog-to-digital converters, wireline receivers, and memory bit-line detectors. However, their nonlinear, time-varying dynamics resulting in discrete output levels have discouraged the use of traditional linear time-invariant (LTI) small-signal analysis and noise simulation techniques. This paper describes a linear, time-varying (LTV) model of clock comparators that can accurately predict the decision error probability without resorting to more general stochastic system models. The LTV analysis framework in conjunction with the linear, periodically time-varying (LPTV) simulation algorithms available from RF circuit simulators can provide insights into the intrinsic sampling and decision operations of clock comparators and the major contribution sources to random decision errors. Two comparators are simulated and compared with laboratory measurements. A 90-nm CMOS comparator is measured to have an equivalent input-referred random noise of 0.73 mVrms for dc inputs, matching simulation results with a short channel excess noise factor ¿ = 2.

Auralisation and psychoacoustic evaluation of traffic noise scenarios

The evaluation of vehicle noise is mostly done using the A‐weighted sound pressure level, e.g., the Lmax for pass‐by noise or the Leq for community noise. Unfortunately, the dB(A)‐value does not reflect the annoyance effect of vehicle noise correctly. During the first phase of the European Research Project QCity a metric for psychoacoustic evaluation of single pass‐by events has been developed. In the next step this metric is adapted for the evaluation of complex traffic scenarios calculated by traffic flow simulations. Psychoacoustic evaluation requires time signals. Single values or third octave spectra are not sufficient to investigate all relevant effects (e.g., annoying time patterns, masking). The time signals are calculated combining advanced resynthesis with exterior noise simulation techniques. Hereby, it is possible to investigate the effect of e.g., low noise surfaces or various traffic control measures (traffic light vs. roundabout). Since a standard traffic scenario includes a very large numb...

Evaluation of compact noise modeling for Si/SiGe HBTs based on hierarchical hydrodynamic noise simulation

The hierarchical hydrodynamic (HD) noise simulation model used in this work allows to generate a complete small-signal noise representation of the device under test. This new noise model based on full-band Monte-Carlo (MC) generated local noise sources in conjunction with transfer function fields is currently the most accurate Si/SiGe HBT noise simulation technique with tolerable CPU requirements. This new efficient numerical noise model is verified by full-band Monte-Carlo device simulations and compared to two well-known compact noise models, the thermodynamic and the SPICE model.

Physics-based simulation techniques for small- and large-signal device noise analysis in RF applications

The paper presents a review on physics-based noise simulation techniques for RF semiconductor devices, starting with the small-signal case but with greater stress on noise in large-signal (quasi)-periodic operation. The nonautonomous (forced) operation case will be considered, which is relevant to all RF applications apart from oscillators. Besides their importance in device design, physics-based noise models can also suggest viable and correct strategies to implement circuit-oriented models, e.g., compact models. From this standpoint, the connection between physics-based and circuit-oriented modeling is discussed both in the small-signal and in the large-signal case, with particular stress on the treatment of colored noise in the large-signal periodic regime.

An accurate and efficient high frequency noise simulation technique for deep submicron MOSFETs

Based on an active transmission line concept and two-dimensional (2-D) device simulations, an accurate and computationally efficient simulation technique for high frequency noise performance of MOSFETs is demonstrated. Using a Langevin stochastic source term model and small-signal equivalent circuit of the MOSFET, three intrinsic noise parameters (/spl gamma/, /spl delta/, and c) for the drain noise and induced gate noise are calculated. Validity and error analysis for the simulation are discussed by comparing the simulation results with theoretical results as well as measured data.

特集：プリント配線板設計と電磁特性 ４． 「シミュレーション技術」 プリント回路におけるノイズシミュレーション技術

特集：プリント配線板設計と電磁特性 ４． 「シミュレーション技術」 プリント回路におけるノイズシミュレーション技術