Noise effect on the recognition of fragmented contour images

We compared the results of recognition of fragmented contour images in the presence of noise and without noise. Both the contour images and the visual noise were synthesized with Gabor elements. The spacing between fragments in contour images and between noise elements, as well as the sizes of images, varied irrespective of one another. The percentage of recognition did not depend on the size of stimuli, but it differed for various objects in the presence and absence of noise. The percentage of recognition was higher for images with lots of turns in the absence of noise and, on the contrary, for images with lengthy contours with a lightly varying curvature in the presence of noise. The thresholds of recognition in noise depended, in general, on the ratio of the spacing between the elements in noise to the spacing between contour fragments.     

Low frequency noise enhances cortisol among noise sensitive subjects during work performance

Salivary free cortisol concentration, rated stress and annoyance were determined in 32 subjects before, during and after carrying out a battery of performance tasks for 2 hours during exposure to ventilation noise, with dominant low frequencies (low frequency noise) or a flat frequency spectrum (reference noise). Both noises had a level of 40 dBA. All subjects were studied on two occasions and were exposed to both noises in strict rotation. Subjects were categorised as high- or low-sensitive to noise in general and low frequency noise in particular on the basis of questionnaires. Cortisol concentrations during the task were not significantly modulated by the noises or related to noise sensitivity alone. The normal circadian decline in cortisol concentration was however significantly attenuated in subjects high-sensitive to noise in general, when they were exposed to the low frequency noise. This noise was rated as more annoying and more disruptive to working capacity than the reference noise. The study showed physiological evidence of increased stress related to noise sensitivity and noise exposure during work. This is the first study to demonstrate an effect of moderate levels of noise on neuroendocrine activity. The impact of long-term exposure to moderate noise levels, and particularly low frequency noise, in the workplace deserves further investigation.     

Controlling visually induced self-motion perception: effect of overlapping dynamic visual noise

The effect of overlapping dynamic visual noise on visually induced self-motion perception (vection) by upward or downward optical flow was tested. The dynamic visual noise consisted of rapidly refreshed sparse random dots. Binocular disparity of the overlapping noise plane was varied. The results showed that when the noise was presented on the flow plane or on a plane farther than the flow plane, vection was totally impaired. This demonstrates that dynamic visual noise is functionally equivalent to static patterns in the vection suppression effect. A possibility of dynamic visual noise as a vection suppressor in an application on a 3-D display is discussed in relation to simulator sickness.     

Ag-AgCl electrode noise in high-resolution ECG measurements

The authors measured the noise and impedance from face-to-face Ag-AgCl electrode pairs, as well as the noise from Ag-AgCl electrodes placed on the human body surface, in the frequency band from 0.5 Hz to 500 Hz, which corresponds to high-resolution ECG measurements. Electrode noise and electrode impedance were measured simultaneously to compare electrode noise with the thermal noise from the real part of electrode impedance. The results show that electrode noise depends on electrode area, electrolytic gel, the patient, and the placement site. In the frequency band from 0.5 Hz to 500 Hz, root-mean-square electrode noise is typically less than 1 microV for electrodes placed face-to-face and ranges from 1 microV to 15 microV for electrodes on the body surface. The noise spectral density increases at low frequencies as 1/fa and it is always higher than the thermal noise from the real part of the electrode impedance. There is a high correlation between electrode dc offset voltage and electrode noise. Thus, offset voltage measurements allow identification of noise from low-noise electrodes.     

Modeling Inter-trial Variability of Saccade Trajectories: Effects of Lesions of the Oculomotor Part of the Fastigial Nucleus

This study investigates the inter-trial variability of saccade trajectories observed in five rhesus macaques (Macaca mulatta). For each time point during a saccade, the inter-trial variance of eye position and its covariance with eye end position were evaluated. Data were modeled by a superposition of three noise components due to 1) planning noise, 2) signal-dependent motor noise, and 3) signal-dependent premotor noise entering within an internal feedback loop. Both planning noise and signal-dependent motor noise (together called accumulating noise) predict a simple S-shaped variance increase during saccades, which was not sufficient to explain the data. Adding noise within an internal feedback loop enabled the model to mimic variance/covariance structure in each monkey, and to estimate the noise amplitudes and the feedback gain. Feedback noise had little effect on end point noise, which was dominated by accumulating noise. This analysis was further extended to saccades executed during inactivation of the caudal fastigial nucleus (cFN) on one side of the cerebellum. Saccades ipsiversive to an inactivated cFN showed more end point variance than did normal saccades. During cFN inactivation, eye position during saccades was statistically more strongly coupled to eye position at saccade end. The proposed model could fit the variance/covariance structure of ipsiversive and contraversive saccades. Inactivation effects on saccade noise are explained by a decrease of the feedback gain and an increase of planning and/or signal-dependent motor noise. The decrease of the fitted feedback gain is consistent with previous studies suggesting a role for the cerebellum in an internal feedback mechanism. Increased end point variance did not result from impaired feedback but from the increase of accumulating noise. The effects of cFN inactivation on saccade noise indicate that the effects of cFN inactivation cannot be explained entirely with the cFN’s direct connections to the saccade-related premotor centers in the brainstem.     

不同类型绿化带对交通噪声的衰减效果比较

为研究绿化带对交通噪声的衰减效应,在北京市郊国道边或市区内有代表性的绿化带设置30 m宽林带23个,测试不同类型林带对实时交通噪声、模拟交通噪声、白噪声和不同频率噪声(125~8 000 Hz)的降噪值,并分析了季节和距噪声源的距离对各林带降噪效果的影响。结果显示:不同林带的降噪效果有明显差异。对于实时交通噪声,降噪效果最佳的是刺槐(Robinia pseudoacacia)纯林和油松-刺柏(Pinus tabulaeformis-Juniperus formosana)混交林,最弱的是旱柳(Salix matsudana)纯林;对于模拟交通噪声,降噪效果最佳的是刺柏-侧柏(Juniperus formosanaPlatycladus orientalis)混交林和国槐(Sophora japonica)纯林,最弱的是旱柳纯林和加杨(Populus×canadensis)纯林;对于白噪声,油松纯林的降噪效果较好,银杏-圆柏(Ginkgo biloba-Sabina chinensis)混交林降噪效果较差。冬季不同林带对不同噪声的衰减效果总体上小于夏季,其中,针叶混交林、针阔叶混交林或针叶纯林在夏、冬季对实时交通噪声和模拟交通噪声或白噪声的降噪效果接近。10 m宽林带的降噪值随距噪声源距离的变化而差异明显,离噪声源越近降噪效果越好。不同林带对中低频率(2 000 Hz以下)噪声的整体降噪效果优于对高频噪声的降噪效果,其中对500 Hz噪声的降噪值最大,对5 000和8 000 Hz噪声的降噪值最小。为了充分发挥绿化带的降噪功能,根据研究结果,建议在公路绿化带建设中应优先选用针叶混交林或分枝高度较低且分枝多、叶片小而密集的树种;绿化带的宽度至少10 m且应规则种植。     

A case study: the effect of visitors on two captive pumas with respect to the time of the day

This study analyzed the effects of noise levels and number of visitors on the behaviors of a mother puma and her daughter in a zoo environment with respect to the time of day. The study monitored visitation (noise and number) over two 1-week periods (4 weeks between periods) and frequency of various puma behaviors (videorecorded). The study analyzed videotaped behavior of the pumas based on the time of day and visitors' number and noise levels. There was a direct association of puma behaviors with visitors' number and noise levels. The daughter puma was the most affected and behavioral changes of both pumas correlated more strongly with the noise level than the number of visitors. The noise level and number of visitors affected the behavior of the mother and her daughter only in the morning. The results of this study indicate that both noise level and number of visitors affected these pumas but revealed the noise as predominant. Moreover, the response of these pumas to visitors depended on the time of the day.     

Airport noise disturbs foraging behavior of Japanese pipistrelle bats

The expansion of anthropogenic noise poses an emerging threat to the survival and reproductive success of various organisms. Previous investigations have focused on the detrimental effects of anthropogenic noise on the foraging behavior in some terrestrial and aquatic animals. Nevertheless, the role of airport noise in impairing foraging activities of most wild animals has been neglected. Here, we aimed to assess whether foraging behavior in free‐living Japanese pipistrelle bats (Pipistrellus abramus) can be disturbed by airport noise. We used audio recording to monitor foraging activities of bats at 11 sites around the runway of a municipal airport. We quantified noise level and spectra, aircraft activity, habitat type, nightly temperature, wind speed, and moon phase for each site. The analysis revealed that noise level and aircraft activity were significant negative predictors for the number of bat passes and feeding buzzes around the runway, even after controlling for the effects of other environmental factors. There was no marked spectral overlap between bat echolocation pulses and airport noise in the presence and absence of low‐flying aircraft. The spectro‐temporal parameters of echolocation vocalizations emitted by bats were dependent on noise level, aircraft activity, and habitat type. These results provide correlative evidence that airport noise can reduce foraging activities of wild pipistrelle bats. Our findings add to the current knowledge of adverse impacts of airport noise on foraging bats in artificial ecosystems and provide a basis for further research on the mechanisms behind noise pollution near airports.     

水下噪音对杂交鲟行为及肠道微生物的影响

为探究水下噪音对杂交鲟行为变化(游泳速率、摄食速率、空间分布)及其肠道微生物的影响,在(145±5) dB, 400 Hz的噪音条件下对杂交鲟进行了0、24h、48h、7d和14d的噪音刺激,随后置于无胁迫噪音的自然环境中恢复48h。结果显示,噪音刺激后杂交鲟游泳速度和摄食速度显著减慢,空间分布发生改变,噪音刺激开始时杂交鲟聚集于远离噪音源的一侧, 3min后却逐渐接近噪音源。噪音对杂交鲟的肠道微生物的丰富度无显著性影响;不同时间段的各组肠道微生物的优势种群存在差异,且随时间变化优势种群反复改变;以上微生物分析结果通过COG预测显示,噪音胁迫48h和7d时“细胞信号传递过程”,“碳水化合物的转运”及“氨基酸的运输和代谢功能”显著低于其他组。结果表明,噪音对杂交鲟摄食速率、游泳速率及空间分布影响显著,改变了其肠道微生物组成和占比,影响了其氨基酸代谢等多条生命活动相关通路。实验模拟了水下各类噪音源的混合噪音对杂交鲟行为和肠道微生物的影响,为探讨杂交鲟的健康生态养殖和逆境生理响应机制提供基础资料。     

北京市3种配置模式绿化带降噪效果的空间变化规律

为明确不同配置模式绿化带对噪声衰减效果的空间变化规律,以北京市的刺槐(Robinia pseudoacacia Linn.)纯林(代表阔叶纯林)、刺槐-小花溲疏(Deutzia parviflora Bunge)混交林(代表阔叶混交林)和侧柏〔Platycladus orientalis(Linn.)Franco〕-圆柏〔Sabina chinensis(Linn.)Ant.〕混交林(代表针叶混交林)3类绿化带为研究对象,设置不同高度、距噪声源不同水平距离和不同噪声频率3组变量,对3类绿化带的降噪值进行比较分析.结果表明:3类绿化带的降噪效果由高至低依次为针叶混交林、阔叶混交林、阔叶纯林.在不同高度和距噪声源不同水平距离处,3类绿化带对不同频率噪声有各自的降噪优势;其中,在高度0.5和1.5 m处,阔叶混交林对250~1000 Hz噪声的衰减效果总体上优于阔叶纯林,而阔叶纯林对4000 Hz的噪声衰减效果却优于阔叶混交林,并且,针叶混交林对250、500、1000和8000 Hz噪声的衰减效果总体上优于阔叶纯林;整体上看,在距噪声源水平距离超过10 m处,3类绿化带对125~1000 Hz噪声的衰减效果最优.相关性分析结果表明:3类绿化带的降噪率与噪声频率呈负相关,与距噪声源水平距离和单位面积三维绿量总体上呈正相关.其中,在高度0.5、1.5和2.5 m处,3类绿化带的降噪率与噪声频率和距噪声源水平距离总体上显著相关;而在高度0.5和1.5 m处,3类绿化带的降噪率与单位面积三维绿量总体上显著相关.从3类绿化带的降噪规律看,在距噪声源水平距离相同的位置,高度越低,绿化带的降噪值越大,其中高度2.5 m以下绿化带的降噪值均较大;在相同高度上,距噪声源水平距离10和15 m处3类绿化带的降噪值总体上较大,但在距噪声源水平距离15和20 m处针叶混交林的降噪值明显大于其他2类绿化带.根据上述研究结果,建议绿化带宽度应在10 m以上,在配置绿化带时,应选择分枝点低、枝叶密度大的树种,且在不影响树木生长的条件下尽量密植并适度配置灌木.     

Discrimination of spectral patterns of sound signals in conditions of interfering noise

The method of probes with rippled spectra makes possible to measure the frequency resolving power (FRP) of human hearing using no frequency-selective masking techniques. This allows studying the influence of interfering noises on the FRP. In conditions of diotic presentation (parallel to both ears), FRP markedly decreases on- or low-frequency noise markedly decreases FRP. The dependence of this effect on sound intensity and noise-to-probe ratio is different for the on- and low-frequence noise, which indicates different mechanisms of action of these two kinds of interfering noise. However, in both cases, a loud enough interfering noise results in complete inability to discriminate the fine spectral pattern of the probe. On the contrary, in conditions of dichotic presentation (the probe to one ear and the noise to the other), the interfering noise does not influence FRP noticeably within a wide range of frequency relations of the probe and noise and noise-to-probe level ratios. Thus, almost entire dichotic release of influence of interfering noise on FRP takes place. This feature can be used for designing bearing aids.     

Use of pseudorandom noise in studies of frequency selectivity: The periphery of the auditory system

Frequency selectivity of single auditory nerve fibers in the rat was studied using pseudorandom noise based on ternary m-sequences as the stimulus, and the results were compared to those of earlier studies in which noise based on binary m-sequences was used. Pseudorandom noise based on ternary m-sequences has fewer anomalies than noise based on binary m-sequences. Detailed tests using linear and nonlinear filters showed that the present method provides accurate measures of bandwidth and center frequency. Period histograms of the response, locked to the periodicity of the noise, were cross-correlated with one period of the noise to obtain estimates of the impulse response function of the peripheral auditory system. Fourier transforms of these cross-correlograms were used as estimates of the filter function of single auditory nerve fibers. The results obtained using ternary noise were not different from previous results showing a downward shift in center frequency and increase in bandwidth with increasing stimulus intensity for fibers with center frequencies between 1000 and 5000 Hz. The difference between spectral selectivity based on phase-locked responses and that based on discharge rate is discussed.     

上海城市绿地植物群落降噪功能及其影响因子

利用因子分析法,对上海19类绿地植物群落30m宽度的噪声相对衰减量与8个群落结构因子的关系进行了分析.结果表明:绿地群落的降噪效果明显,其与草坪的降噪效果存在极显著差异(P<0.01),声波在绿地中有额外的声衰减.3组不同降噪能力绿地群落的30m噪声相对衰减量分别为≥10dB(A)、6～10dB(A)和?6dB(A);影响绿地群落降噪效果的结构因子为叶面积指数、群落平均枝下高、平均高度、盖度和平均冠幅,它们与噪声相对衰减量的相关系数分别为0.343、0.318、0.285、0.226和0.193.结构因子的累积贡献率达65.47%.在降噪绿地设计中应着重考虑这5个结构因子.     

Dispersal, colored environmental noise, and spatial synchrony in population dynamics: analyzing a discrete host–parasitoid population model

Spatial synchrony is common, and its influences and causes have attracted the interest of ecologists. Spatially correlated environmental noise, dispersal, and trophic interactions have been considered as the causes of spatial synchrony. In this study, we developed a spatially structured population model, which is described by coupled-map lattices. Our recent investigation showed that trophic correlation of environmental noise was another important factor that affects spatial synchrony. As a supplement, we considered the influence of the color of the environmental noise on the spatial synchrony in this study. The noise color refers to the temporal correlation in the time series data of the noise, and is expressed as the degree of (first-order) autocorrelation for autoregressive noise. Patterns of spatial synchrony were considered for stable, periodic (quasi-periodic), and chaotic population dynamics. Numerical simulations verified that the color of the environmental noise is another mechanism that causes spatial synchrony. Generally, the effect of the color of the noise on the synchrony is dependent on the type of dynamics (stable, cyclic, chaotic) present in the population. For cyclic dynamics, simulation results clearly demonstrate that reddened noise has higher synchrony than white noise. The importance of our research is that it enriches the theory of potential causes of spatial synchrony.     

Synchrony of spatial populations induced by colored environmental noise and dispersal

Spatial synchrony of oscillating populations has been observed in many ecological systems, and its influences and causes have attracted the interest of ecologists. Spatially correlated environmental noises, dispersal, and trophic interactions have been considered as the causes of spatial synchrony. In this study, we develop a spatially structured population model, which is described by coupled-map lattices and incorporates both dispersal and colored environmental noise. A method for generating time series with desired spatial correlation and color is introduced. Then, we use these generated time series to analyze the influence of noise color on synchrony in population dynamics. The noise color refers to the temporal correlation in the time series data of the noise, and is expressed as the degree of (first-order) autocorrelation for autoregressive noise. Patterns of spatial synchrony are considered for stable, periodic and chaotic population dynamics. Numerical simulations verify that environmental noise color has a major influence on the level of synchrony, which depends strongly on how noise is introduced into the model. Furthermore, the influence of noise color also depends on patterns of dispersal between local populations. In addition, the desynchronizing effect of reddened noise is always weaker than that of white noise. From our results, we notice that the role of reddened environmental noise on spatial synchrony should be treated carefully and cautiously, especially for the spatially structured populations linked by dispersal.     

Noise-induced reduction in the attack rate of a planktivorous freshwater fish revealed by functional response analysis

1. Anthropogenic noise can affect animals physically, physiologically, and behaviourally. Although individual responses to noise are well documented, the consequences in terms of community structure, species coexistence, and ecosystem functioning remain fairly unknown.
2. The impact of noise on predation has received a growing interest and alterations in trophic links are observed when animals shift from foraging to stress-related behaviours, are distracted by noise, or because of acoustic masking. However, the experimental procedures classically used to quantify predation do not inform on the potential demographic impact on prey.
3. We derived the relationship between resource use and availability (the functional response) for European minnows (Phoxinus phoxinus) feeding on dipteran larvae (Chaoborus sp.) under two noise conditions: ambient noise and ambient noise supplemented with motorboat noise. The shape and magnitude of the functional response are powerful indicators of population outcomes and predator–prey dynamics. We also recorded fish behaviour to explore some proximate determinants of altered predation.
4. For both noise conditions, fish displayed a saturating (type II) functional response whose shape depends on two parameters: attack rate and handling time. Boat noise did not affect handling time but significantly reduced attack rate, resulting in a functional response curve of the same height but with a less steep initial slope. Fish exhibited a stress-related response to noise including increased swimming distance, more social interactions, and altered spatial distribution.
5. Our study shows the usefulness of the functional response approach to study the ecological impacts of noise and illustrates how the behavioural responses of predators to noise can modify the demographic pressure on prey. It also suggests that prey availability might mediate the negative effect of noise on predation. Community outcomes are expected if the reduced consumption of the main food sources goes with the overconsumption of alternative food sources, changing the distribution pattern of interaction strengths. Predation release could also trigger a trophic cascade, propagating the effect of noise to lower trophic levels.

     

A synthesis of two decades of research documenting the effects of noise on wildlife

Global increases in environmental noise levels – arising from expansion of human populations, transportation networks, and resource extraction – have catalysed a recent surge of research into the effects of noise on wildlife. Synthesising a coherent understanding of the biological consequences of noise from this literature is challenging. Taxonomic groups vary in auditory capabilities. A wide range of noise sources and exposure levels occur, and many kinds of biological responses have been observed, ranging from individual behaviours to changes in ecological communities. Also, noise is one of several environmental effects generated by human activities, so researchers must contend with potentially confounding explanations for biological responses. Nonetheless, it is clear that noise presents diverse threats to species and ecosystems and salient patterns are emerging to help inform future natural resource‐management decisions. We conducted a systematic and standardised review of the scientific literature published from 1990 to 2013 on the effects of anthropogenic noise on wildlife, including both terrestrial and aquatic studies. Research to date has concentrated predominantly on European and North American species that rely on vocal communication, with approximately two‐thirds of the data set focussing on songbirds and marine mammals. The majority of studies documented effects from noise, including altered vocal behaviour to mitigate masking, reduced abundance in noisy habitats, changes in vigilance and foraging behaviour, and impacts on individual fitness and the structure of ecological communities. This literature survey shows that terrestrial wildlife responses begin at noise levels of approximately 40 dBA, and 20% of papers documented impacts below 50 dBA. Our analysis highlights the utility of existing scientific information concerning the effects of anthropogenic noise on wildlife for predicting potential outcomes of noise exposure and implementing meaningful mitigation measures. Future research directions that would support more comprehensive predictions regarding the magnitude and severity of noise impacts include: broadening taxonomic and geographical scope, exploring interacting stressors, conducting larger‐scale studies, testing mitigation approaches, standardising reporting of acoustic metrics, and assessing the biological response to noise‐source removal or mitigation. The broad volume of existing information concerning the effects of anthropogenic noise on wildlife offers a valuable resource to assist scientists, industry, and natural‐resource managers in predicting potential outcomes of noise exposure.     

Extrinsic noise passing through a Michaelis-Menten reaction: A universal response of a genetic switch

The study of biochemical pathways usually focuses on a small section of a protein interactions network. Two distinct sources contribute to the noise in such a system: intrinsic noise, inherent in the studied reactions, and extrinsic noise generated in other parts of the network or in the environment. We study the effect of extrinsic noise entering the system through a nonlinear uptake reaction which acts as a nonlinear filter. Varying input noise intensity varies the mean of the noise after the passage through the filter, which changes the stability properties of the system. The steady-state displacement due to small noise is independent on the kinetics of the system but it only depends on the nonlinearity of the input function.For monotonically increasing and concave input functions such as the Michaelis-Menten uptake rate, we give a simple argument based on the small-noise expansion, which enables qualitative predictions of the steady-state displacement only by inspection of experimental data: when weak and rapid noise enters the system through a Michaelis-Menten reaction, then the graph of the system's steady states vs. the mean of the input signal always shifts to the right as noise intensity increases.We test the predictions on two models of lac operon, where TMG/lactose uptake is driven by a Michaelis-Menten enzymatic process. We show that as a consequence of the steady state displacement due to fluctuations in extracellular TMG/lactose concentration the lac switch responds in an asymmetric manner: as noise intensity increases, switching off lactose metabolism becomes easier and switching it on becomes more difficult.     

顺铂和噪声联合作用对听觉器官的影响

研究了顺铂与噪声联合作用对耳蜗的毒性,发现联合作用后听阈偏移大于单独顺铂作用后阈移和单独噪声作用后阈移的总和。此外,联合作用后听觉脑干诱发电位振幅下降非常明显。结果表明,顺铂与噪声联合作用对内耳的毒性有协同作用。     

Exposure to noise pollution across North American passerines supports the noise filter hypothesis

The noise filter hypothesis predicts that species using higher sound frequencies should be more tolerant of noise pollution, because anthropogenic noise is more intense at low frequencies. Recent work analysed continental‐scale data on anthropogenic noise across the USA and found that passerine species inhabiting more noise‐polluted areas do not have higher peak song frequency but have more complex songs. However, this metric of song complexity is of ambiguous interpretation, because it can indicate either diverse syllables or a larger frequency bandwidth. In the latter case, the finding would support the noise filter hypothesis, because larger frequency bandwidths mean that more sound energy spreads to frequencies that are less masked by anthropogenic noise. We reanalysed how passerine song predicts exposure to noise using a more thorough dataset of acoustic song measurements, and showed that it is large frequency bandwidths, rather than diverse syllables, that predict the exposure of species to noise pollution. Given that larger bandwidths often encompass higher maximum frequencies, which are less masked by anthropogenic noise, our result suggests that tolerance to noise pollution might depend mostly on having the high‐frequency parts of song little masked by noise, thus preventing acoustic communication from going entirely unnoticed at long distances.