Relativistic dynamical reduction models: General framework and examples

The formulation of a relativistic theory of state-vector reduction is proposed and analyzed, and its conceptual consequences are elucidated. In particular, a detailed discussion of stochastic invariance and of local and nonlocal aspects at the level of individual systems is presented.     

A fuzzy rule based framework for noise annoyance modeling

Predicting the effect of noise on individual people and small groups is an extremely difficult task due to the influence of a multitude of factors that vary from person to person and from context to context. Moreover, noise annoyance is inherently a vague concept. That is why, in this paper, it is argued that noise annoyance models should identify a fuzzy set of possible effects rather than seek a very accurate crisp prediction. Fuzzy rule based models seem ideal candidates for this task. This paper provides the theoretical background for building these models. Existing empirical knowledge is used to extract a few typical rules that allow making the model more specific for small groups of individuals. The resulting model is tested on two large-scale social surveys augmented with exposure simulations. The testing demonstrates how this new way of thinking about noise effect modeling can be used in practice both in management support as a "noise annoyance adviser" and in social science for testing hypotheses such as the effect of noise sensitivity or the degree of urbanization.     

On the prediction of impact noise,II: Ringing noise

The introduction of legislation regarding the limits of noise in factories has led to the need for the prediction of likely noise levels produced by a machine at the design stage. Part I was concerned with the noise produced by impacting bodies due to the high surface accelerations during the contact period. Part II is concerned with the noise arising from the subsequent free vibration. The radiation efficiency of simple components having various modes of vibration is discussed and presented in the form of charts, which it is hoped will enable the machine designer to predict the ringing noise of a machine at its design stage, once the surface area and mean square surface velocity have been established.     

On the prediction of impact noise,I: Acceleration noise

The introduction of legislation regarding the limits of noise in factories has led to the need for prediction of likely noise levels produced by a machine at its design stage. This paper, the first of a series, is concerned with the noise generated by impacting bodies due to the high surface accelerations during the contact period. An account is presented of the theoretical development and experimental validation of curves for the prediction of peak sound pressure and radiated energy for collisions of compact bodies which are incapable of flexural motions. It is shown that acceleration noise energy is of the same order of magnitude as that due to ringing, that it cannot be greater than 1·5 × 10^?4 times the kinetic energy input at impact, and that it falls off rapidly as the normalized contact time increases above a critical value.     

Variation with distance of aircraft noise impact parameters

Recent developments in the use of statistical energy analysis for the prediction of vibration levels on spacecraft components have led to the need to measure the frequency averaged modal density. In the case of structural components having low damping it has been extremely difficult to make a successful measurement by using existing techniques. Success has usually been achieved by the addition of damping tape to the structure under test. The transient testing technique also requires extremely long data lengths on lightly damped structures, which can lead to a requirement for Fourier transforms considerably longer than normally available. In the technique described here random excitation and extremely short data lengths are used; the technique is shown to give good results on structures with no additional damping material, with a considerable saving in time and expense not only during the experimentation but also during data processing.     

Context sensitive noise impact mapping

Apartments that are exposed to the same level of road traffic noise on front of the most exposed façade often have very different neighbourhood soundscapes. In the first part of this paper, a neighbourhood soundscape adjusted exposure indicator, NAL_den, is derived. NAL_den-values are designed to be used as input to traditional exposure-effect relationships to improve annoyance impact estimates. In the second part, generic spatial procedures are developed and implemented. These produce map presentations in the form of contiguous neighbourhood quality areas. The quality of each neighbourhood is determined from the predicted annoyance impacts for residents. Noise impact maps provide experts, politicians, and the public with high-level impact visualizations of condensed status, “what-if” and scenario information. Results and illustrations are based on data from the Norwegian socio-environmental survey database, and a comprehensive national noise mapping effort. The methodology should work well for mapping Europe’s “black” and “grey” areas.     

On the prediction of impact noise,part VI: Distribution of acceleration noise with frequency with application to bottle impacts

The spectral distribution of the acceleration noise, as defined in Part I of this series, is obtained using both the pressure waveform expressions and the spatial averaged velocity on the surface of the body, together with a radiation efficiency associated with the rigid body movement of the object. This distribution with frequency is shown to be mainly dependent on the size of the body and the duration of the transient and is independent of the body shape detail and the exact shape of the transient. The spectral distribution of acceleration noise is important in the case of impact of structures whose first ringing natural frequency is within the frequency range under investigation. Under such circumstances, it is important to estimate the response of the structure below this resonant frequency. In this paper this is investigated to show that the response, and hence the noise radiated from a structure below the first ringing frequency, is low and the noise in this frequency range is mostly due to acceleration noise. These results are verified in the case of bottle clashes.     

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.     

我国机场噪声评价量与噪声影响的定量关系

本文对我国机场航空噪声评价量LWECPN(计权等效连续感觉噪声级)与国外常用的评价量LDN(昼夜等效声级)的内涵进行了分析，导出了两者之间的关系，并借助这一关系和国外研究成果得到了机场周边社区人群中受到航空噪声强烈干扰的人数比例与LWECPN的关系式。     

On the prediction of impact noise,Part IX: The noise from punch presses

The punch press is a further classical example of impact noise: the force is built up in the punch relatively slowly, and the whole machine is strained until the load on the material being punched reaches a yield and shortly afterwards a fracture level. At this stage the strain energy in the machine and its workpiece must be redistributed and this leads to vibration of the whole machine and to noise radiation. In this paper work which has been carried out at ISVR over a number of years is presented. It describes the way the Energy Accountancy Equation [1] can be modified to relate the noise radiated directly to the sum of the squares of the large rates of change of force against time, and illustrates clearly the way that noise control, with use of passive or active methods in designing the punch tooling, can be related directly to the one parameter 10 log Σ[f(t)]_max². It is shown that noise levels can be reduced by up to 30 dB under ideal conditions by fracture pulse tailoring while still cutting metal, but that more realistically, 10 dB reductions may be obtained below those of current practice by practical tool design. An explanation is given of why large open presses are never likely to achieve the proposed factory noise levels and that the noise from double-sided presses can be controlled effectively by tooling modifications and by the addition of damping. The paper describes work carried out on passive and active cancellation systems used to arrest and springback of the press structure following workpiece material fracture and explains the practical limitations of such systems. Active techniques are limited by the difficulties obtained, with brittle hard materials, of finding a trigger and load freezing system which can operate fast enough to reduce adequately the force parameter 10 log Σ (f_max(t))². Where punching finish allows, it has been found that well-designed shear and/or cutting with low percentage clearance is superior to active cancellation, since this provides a surer method of reducing the above force parameter, especially for harder materials. The Energy Accountancy Equation suggests that the use of increased structural damping can be an effective method of noise reduction, particularly if the punch press structure is initially only lightly damped. Experiments on a third-scale model of a 200 tonne double-sided press suggest that this damping needs to be added selectively in areas where the vibrational energy density is high and coincides with areas of high noise radiation. Thus, in the experiments described, 12 dB reduction has been obtained under such conditions, only 1 or 2 dB reduction being obtained when damping of the base plate has been unaltered.     

Modeling of the roundabout noise impact

A roundabout is a very popular tool used by town planners for carrying smooth and stationary road traffic flow. In this study it is shown that the replacement of a classical road intersection by a roundabout, under certain conditions, may produce a traffic noise decrease. These conditions are expressed in terms of the roundabout speed and the receiver location. The A-weighted sound exposure level is used to describe noise reduction.     

Community noise exposure and stress in children

Although accumulating evidence over the past two decades points towards noise as an ambient stressor for children, all of the data emanate from studies in high-intensity, noise impact zones around airports or major roads. Extremely little is known about the nonauditory consequences of typical, day-to-day noise exposure among young children. The present study examined multimethodological indices of stress among children living under 50 dB or above 60 dB (A-weighted, day-night average sound levels) in small towns and villages in Austria. The major noise sources were local road and rail traffic. The two samples were comparable in parental education, housing characteristics, family size, marital status, and body mass index, and index of body fat. All of the children were prescreened for normal hearing acuity. Children in the noisier areas had elevated resting systolic blood pressure and 8-h, overnight urinary cortisol. The children from noisier neighborhoods also evidenced elevated heart rate reactivity to a discrete stressor (reading test) in the laboratory and rated themselves higher in perceived stress symptoms on a standardized index. Furthermore girls, but not boys, evidenced diminished motivation in a standardized behavioral protocol. All data except for the overnight urinary neuroendocrine indices were collected in the laboratory. The results are discussed in the context of prior airport noise and nonauditory health studies. More behavioral and health research is needed on children with typical, day-to-day noise exposure.     

Impulsive noise generated in impact forming machinery

The drop hammer accelerated by falling freely and used for cold working operation produces intense, short-duration, impact noise and is a serious hazard to the hearing mechanism. Some of its aspects relating to generation and reduction are explored. Momentum just before impact can be increased by increasing input energy in the system or keeping constant energy by the various combinations of masses and velocities. In the first case, when momentum increases, the force between the colliding bodies increases, and sound pressure level versus frequency response becomes correspondingly higher but, in the second case, when momentum increases, force decreases and sound pressure level versus frequency response becomes correspondingly lower. Impact-noise can be reduced to a great extent by regarding the falling-weight as a reverberant room. It is the major contributor to noise.     

The development of a practical framework for strategic noise mapping

There currently exist a number of commercial tools which may be used to develop strategic noise maps in an effort to satisfy the requirements of EU Directive 2002/49/EC. However, these tools may not be readily available to local authorities with limited resources. This paper investigates the possibility of developing a simplified alternative to using detailed commercial software for the creation of strategic noise maps. In-house noise prediction software was used to calculate a noise map of Dublin city centre and results were compared to those of commercial standard software. The in-house software tool was then used to assess the impact of various source-dependent action plans in a time-efficient and practical manner. Measurements were also carried out at various locations throughout the test area, which were then used to investigate the accuracy of predictions. Finally, a hybrid approach to developing a strategic noise map by integrating measurements taken on-site with predictions was developed. This approach was applied to the test area and yielded a refined noise map that presented noise levels which were more reflective of the measured levels recorded on-site. This demonstrated that the method could be used to determine noise levels that would be representative of the acoustic environment experienced on-site.     

Saliency Snake: A unified framework with adaptive initial curve

Active contour model also known as Snake, is a popular approach for contour extraction and image segmentation. However, some existing active contour models are sensitive to the initial curve, which is usually required to be placed near the true object contour. To address this problem, this paper proposes a novel active contour model with adaptive initial curve, namely Saliency Snake. Taking visual saliency into consideration, prior shape information of the interested object is incorporated explicitly into the energy functional of Saliency Snake. Such improvement facilitates active contour evolution and leads to fast and automatic segmentation. Experiment results demonstrate that the proposed Saliency Snake can achieve superior segmentation performance both in terms of accuracy and efficiency.