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Computation of vortical flow and flow induced noise by large eddy simulation with FW-H acoustic analogy and Powell vortex sound theory 被引量:8
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作者 张楠 谢华 +1 位作者 王星 吴宝山 《Journal of Hydrodynamics》 SCIE EI CSCD 2016年第2期255-266,共12页
The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation (LES) with the FW-H acoustic analogy and the other is the LES with the Powe... The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation (LES) with the FW-H acoustic analogy and the other is the LES with the Powell vortex sound theory, in order to compare the accuracies of their predictions. The vortical structures around the rod-airfoil are computed by the LES and captured by the vortex identification (Q). The acoustic predictions are verified by the measurements. It is shown that the computed results by the two hybrid approa- ches (LES and FW-H, LES and Powell) are very similar. Both are shown to be satisfactory in the prediction of the noise generated by an unsteady flow. Subsequently, the numerical simulations of the wall pressure fluctuations and the flow-induced noise of a NACA0015 airfoil are made by the two hybrid approaches. At two angles of attack ( 0~ and 8~ ), the wall pressure fluctuations of the NACA0015 airfoil are computed. The obtained power spectra of the wall pressure fluctuations are analyzed and compared with the measured data. And the vortical structures around the airfoil at two angles of attack are simulated and analyzed. After that, the flow induced noises of the NACA0015 airfoil at two angles of attack are predicted by the two hybrid approaches (LES and FW-H, LES and Powell). The radiated sound spectra are analyzed and compared with the experimental data. Comparisons show that both are robust, credible and satisfactory in the numerical prediction of the flow induced noise. All numerical simulations are carried out by parallel processing in the Wuxi supercomputing center. 展开更多
关键词 flow induced noise large eddy simulation (LES) FW-H acoustic analogy powell vortex sound theory rod-airfoil airfoil
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Suppression of backscattering induced noise by the sideband locking technique in a resonant fiber optic gyroscope 被引量:6
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作者 刘宁 牛燕雄 +2 位作者 冯丽爽 焦洪臣 王潇 《Chinese Optics Letters》 SCIE EI CAS CSCD 2018年第1期38-42,共5页
Polarization fluctuation induced noise and backscattering-induced noise are the dominant noises in resonant fiber optic gyroscopes. This Letter proposes a new method to suppress the carrier and backscattering induced ... Polarization fluctuation induced noise and backscattering-induced noise are the dominant noises in resonant fiber optic gyroscopes. This Letter proposes a new method to suppress the carrier and backscattering induced noise by the sideband locking technique. Besides choosing an optimized modulation depth and different clockwise and counterclockwise modulation frequencies, the sideband is locked to the cavity resonance. With the proper modulation frequency, the carrier frequency component locates at a position far away from the resonant frequency, and then it is suppressed by the cavity itself, which can be taken as a bandpass filter. The amplitude of the carrier frequency can be suppressed by 20–25 d B additionally by the cavity and the total intensity suppression ratio can reach 115.74 d B. The backscattering induced noise can be eliminated for the adoption of different frequencies. The method can realize a stable and high suppression ratio without high requirements for parameter accuracy or device performance. 展开更多
关键词 Suppression of backscattering induced noise by the sideband locking technique in a resonant fiber optic gyroscope CCW
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Induced noise of impeller stuck and passive rotation state in multi-stage pump without power drive under natural flow conditions
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作者 Run-ze Zhou Hou-lin Liu +4 位作者 Ru-nan Hua Liang Dong Kim Tiow Ooi Cui Dai Si-yuan Hu 《Journal of Hydrodynamics》 SCIE EI CSCD 2023年第5期1008-1026,共19页
The natural flow cooling strategy is commonly employed in modern high-speed vessels and nuclear-powered submarines. These vessels rely on the energy generated by their own speed to drive the cooling system and supply ... The natural flow cooling strategy is commonly employed in modern high-speed vessels and nuclear-powered submarines. These vessels rely on the energy generated by their own speed to drive the cooling system and supply cooling water to the condenser. The circulating pump, which operates without a motor drive under natural flow conditions, is a large resistance component in the cooling system. However, it is also the primary noise source, significantly impacting the vessel’s safe operation and acoustic stealth performance. This study investigates the induced noise characteristics of a multi-stage pump under natural flow conditions by experiment, computational fluid dynamics (CFD), and acoustic finite element method. The analysis encompasses the distribution of the flow field, variations in acoustic power, spectral features of flow-induced noise, and directivity of external field radiation noise under different natural flow conditions. The results show that the acoustic power distribution is correlated with the flow field. When the impeller is stuck, the noise sources primarily concentrate in the flow separation area at the blade’s leading edge, the interface area between the impeller and the guide vane, and the flow shock area inside the guide vane. Conversely, when the impeller rotates passively, the blade wake area has a higher acoustic power. The flow noise spectrum under natural flow conditions mainly exhibits broadband and discrete characteristics. Additionally, the pump structure influences the external field radiation noise, and its directivity varies with different flow rates and characteristic frequencies. This study provides valuable insights into optimal design to reduce the noise of the circulating pump in the vessel’s natural flow cooling system. It is essential for ensuring the safe operation and acoustic stealth performance of high-speed vessels and nuclear-powered submarines. 展开更多
关键词 Natural flow condition multi-stage pump flow induced noise acoustic power radiation noise directivity
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Entropic noise induced stability and double entropic stochastic resonance induced by correlated noises 被引量:2
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作者 曾春华 王华 王辉涛 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第5期146-152,共7页
For the activated dynamics of a Brownian particle moving in a confined system with the presence of entropic barriers, this paper investigates a periodic driving and correlations between two noises. Within the two-stat... For the activated dynamics of a Brownian particle moving in a confined system with the presence of entropic barriers, this paper investigates a periodic driving and correlations between two noises. Within the two-state approximation, the explicit expressions of the mean first passage time (MFPT) and the spectral power amplification (SPA) axe obtained, respectively. Based on the numerical computations, it is found that: (i) The MFPT as a function of the noise intensity exhibits a maximum with the positive correlations between two noises (λ〉0), this maximum for MFPT shows the characteristic of the entropic noise induced stability (ENIS) effect. The intensity A of correlations between two noises can enhance the ENIS effect. (ii) The SPA as a function of the noise intensity exhibits a double-peak by tuning the noise correlation intensity λ, i.e., the existence of a double-peak behaviour is the identifying characteristic of the double entropic stochastic resonance phenomenon. 展开更多
关键词 correlated noises confined system entropic noise induced stability double entropic stochastic resonance ]
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Noise Induced Hearing Loss in Children:Preventing the Silent Epidemic
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作者 William Hal Martin Judith Sobel +1 位作者 Susan E. Griest Linda Howarth 《Journal of Otology》 2006年第1期11-21,共11页
Noise-induced hearing loss and related tinnitus are often unrecognized problems, especially in non-occupational settings. Research indicates that increasing numbers of children and adolescents have or are acquiring no... Noise-induced hearing loss and related tinnitus are often unrecognized problems, especially in non-occupational settings. Research indicates that increasing numbers of children and adolescents have or are acquiring noise induced hearing losses. Noise induced hearing loss can almost completely be prevented with simple precautionary measures. Educational programs rarely exist outside of those mandated in occupational settings. Health Communication theory can be applied to hearing health for developing effective loss prevention programs. Dangerous Decibels is one example of an effective multi-disciplinary effort to develop and disseminated prevention strategies. 展开更多
关键词 noise induced hearing loss TINNITUS prevention health communication MUSEUM classroom education CHILDREN dangerous decibels
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A Systematical Approach for Noise in CMOS LNA 被引量:1
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作者 冯东 石秉学 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2005年第3期487-493,共7页
A systematic approach is used to analyze the noise in CMOS low noise amplifier(LNA),including channel noise and induced gate noise in MOS devices.A new analytical formula for noise figure is proposed.Based on this for... A systematic approach is used to analyze the noise in CMOS low noise amplifier(LNA),including channel noise and induced gate noise in MOS devices.A new analytical formula for noise figure is proposed.Based on this formula,the impacts of distributed gate resistance and intrinsic channel resistance on noise performance are discussed.Two kinds of noise optimization approaches are performed and applied to the design of a 5 2GHz CMOS LNA. 展开更多
关键词 amplifier noise channel noise channel resistance induced gate noise low noise amplifier noise optimization
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Spatial learning and memory deficits in young adult mice exposed to a brief intense noise at postnatal age 被引量:3
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作者 Shan Tao Lijie Liu +6 位作者 Lijuan Shi Xiaowei Li Pei Shen Qingying Xun Xiaojing Guo Zhiping Yu Jian Wang 《Journal of Otology》 CSCD 2015年第1期21-28,共8页
Noise pollution is a major hazardous factor to human health and is likely harmful for vulnerable groups such as pre-term infants under lifesupport system in an intensive care unit. Previous studies have suggested that... Noise pollution is a major hazardous factor to human health and is likely harmful for vulnerable groups such as pre-term infants under lifesupport system in an intensive care unit. Previous studies have suggested that noise exposure impairs children’s learning ability and cognitive performance and cognitive functions in animal models in which the effect is mainly attributed to the oxidant stress of noise on the cognitive brain. The potential role of noise induced hearing loss(NIHL), rather than the oxidant stress, has also been indicated by a depression of neurogenesis in the hippocampus long after a brief noise exposure, which produces only a tentative oxidant stress. It is not clear if noise exposure and NIHL during early development exerts a long term impact on cognitive function and neurogenesis towards adulthood. In the present study, a brief noise exposure at high sound level was performed in neonatal C57BL/6J mice(15 days after birth) to produce a significant amount of permanent hearing loss as proved 2 months after the noise. At this age, the noise-exposed animals showed deteriorated spatial learning and memory abilities and a reduction of hippocampal neurogenesis as compared with the control. The averaged hearing threshold was found to be strongly correlated with the scores for spatial learning and memory. We consider the effects observed are largely due to the loss of hearing sensitivity, rather than the oxidant stress, due to the long interval between noise exposure and the observations. 展开更多
关键词 noise induced hearing loss Neonatal mice LEARNING
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Cochlear Synaptopathy Following Noise Exposure in Guinea Pigs: Its Electrophysiological and Histological Assessments
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作者 Parvane Mahdi Akram Pourbakht +3 位作者 Vahid Pirhajati Mahabadi Alireza Karimi Yazdi Mahtab Rabbani Anari Mohammad Kamali 《Sound & Vibration》 EI 2020年第3期163-177,共15页
Exposure to high level of noise,may cause the permanent cochlear synaptic degeneration.In present study,a model of noise induced cochlear synaptopathy was established and the electrophysiological and histological metr... Exposure to high level of noise,may cause the permanent cochlear synaptic degeneration.In present study,a model of noise induced cochlear synaptopathy was established and the electrophysiological and histological metrics for its assessment was designed.6 guinea pigs were subjected to a synaptopathic noise(octave band of 4 kHz at 104 dB SPL,for 2-h).The amplitude growth curve of Auditory Brainstem Response(ABR)wave-I and wave-III latency shift in presence of noise were calculated.These indexes were considered in pre-exposure,1 day post exposure(1DPE),1 week post exposure(1WPE)and 1 month post exposure(1MPE)to noise.Finally,the samples were histologically analyzed.ABR wave-I amplitude was different between pre and 1DPE(p-value≤0.05).However,at 1WPE,it was recovered at low intensities but at 70 dB SPL and above,the differences persisted even till 1MPE.In masked ABR,the latency shift of wave-III was different between pre and 3 post exposure assessments(p-value≤0.05).Electro-microscopic analysis confirmed the synaptic degeneration,as the ribbons were larger than normal,hollow inside,and spherical and irregular in shape,also,the post synaptic density was abnormally thick and missed its flat orientation.These data revealed that noise at level below that can produce permanent hearing loss,can incur synaptic injury.So,noise is considered to be more damaging than previously thought.Accordingly,designing tools for clinical assessment of synaptopathy is beneficial in comprehensive auditory evaluation of those with history of noise exposure and also in hearing protection planning. 展开更多
关键词 Cochlear synaptopathy noise induced hearing loss hidden hearing loss EXCITOTOXICITY hearing protection
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Noise Exposure and Its Auditory Effect on Industrial Workers
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作者 Ifeoluwa Victor Owolawi 《International Journal of Otolaryngology and Head & Neck Surgery》 2021年第5期365-375,共11页
This paper analyzes the effect of exposure to noise among industrial workers in Nigeria to discover the level of exposure to noise that causes auditory defects or noise-induced hearing loss (NIHL), this paper primaril... This paper analyzes the effect of exposure to noise among industrial workers in Nigeria to discover the level of exposure to noise that causes auditory defects or noise-induced hearing loss (NIHL), this paper primarily covers the evaluation of hearing impairment and its severity on exposure to loud sounds (acoustic trauma) and the role of hearing protective devices for industrial workers for prevention of Noise Induced Hearing Loss (NIHL). The paper also discusses the findings and guides as preventive methods for such industries. A total sample of seventy (70) workers were selected from three (3) manufacturing industries for this study. This study revealed a statistically significant difference in the hearing threshold within the selected industries over the selected period of time relating to the theory of excessive noise present in a given environment tends to affect people or in this case study employees hearing if proper hearing protection isn’t used for prolonged hours or time, the study also surveys the various effect of noise on human health including various steps of noise control in such settings. 展开更多
关键词 noise noise induced Hearing Loss NRR Auditory System HEARING Hearing Protective Devices Acoustic Trauma
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Prediction of line-spectrum noise induced by high speed vehicle counter-rotation propellers in water
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作者 ZHU Xiqing WU Wusheng(China Ship Scientific Research Center Jiangsu 214082) 《Chinese Journal of Acoustics》 1998年第1期37-48,共12页
Line-Spectrum noise of counter-rotation propellers has constructed the main part of the radiated noise of high speed vehicles in water. The line-spectrum noise of the counter-rotation propellers is due to the interact... Line-Spectrum noise of counter-rotation propellers has constructed the main part of the radiated noise of high speed vehicles in water. The line-spectrum noise of the counter-rotation propellers is due to the interaction between fore or aft propeller and wake of the vehicle,and the interaction between fore and aft propeller. Based on a combination of the lifting surface theory and acoustic method, the prediction of line-spectrum noise is presented in this paper.Theoretical calculation method, characteristics and numerical prediction of the line-spectrum noise are detailed too. The effect of different wake and different distance between fore and aft propeller on the propeller noise is also studied by numerical method. The agreement of predicted results compared with existing experimental data is quite satisfactory. 展开更多
关键词 LINE Prediction of line-spectrum noise induced by high speed vehicle counter-rotation propellers in water high
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Hidden Hearing Loss: Causes, Current Knowledge, and Future Directions
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作者 Alexandra Jalkh 《International Journal of Otolaryngology and Head & Neck Surgery》 2023年第3期107-123,共17页
Introduction: Hidden hearing loss (HHL) is a type of auditory disorder that affects the auditory neural processing and hearing sensitivity in subjects with normal hearing thresholds. Unlike central auditory processing... Introduction: Hidden hearing loss (HHL) is a type of auditory disorder that affects the auditory neural processing and hearing sensitivity in subjects with normal hearing thresholds. Unlike central auditory processing disorders, HHL happens when the cochlea (the peripheral auditory organ) is affected. There are several known risk factors to HHL which includes noise exposure, ototoxic drugs, and peripheral neuropathies, and age. Recent studies have shed light on this type of hearing loss, its etiology, prevalence, and how it can affect the auditory acuity in humans. Methods: This paper covers the current research regarding HHL, its causes, the different mechanisms involved in this disorder, and the diagnosis and potential treatments related to it. We will delve deeply into different researches concerning HHL. 4 articles from 285 were selected focusing on normal hearing individuals with bad speech intelligibility were discussed in this paper. In addition, articles discussing the effects of noise exposure on hearing impaired individuals were not considered as this study solely aims to focus on normal hearing sensitivity individuals with HHL, resulting in 4 articles from 285. Results: Numerous literatures over the decades have suggested that HHL is due to the degeneration of cochlear ribbon synapses, or hair cells synapses without hair cell damage. Their association with HHL was noted several times through this study, whether we were studying the effect of noise exposure, of age, or of ototoxicity. In all cases, no significant hair cell damage was observed, and normal thresholds were recovered. However, a decline in the amplitude of Auditory Brainstem Response (ABR) peak I from auditory nerve (AN) responses in noise exposed subjects and a decline in compound action potential (CAP) was measured when certain drugs were applied to the round window of Guinea pigs. Conclusion: Most studies, have proven that cochlear synaptophysin is the major contributor to noise induced, age, and ototoxic related HHL. There are several audiometric tests that were used to help identify HHL including Puretone audiometry in background noise, ABR, CAP, Distortion Product Otoacoustic Emission (DPOAE). 展开更多
关键词 Hidden Hearing Loss Speech Testing Speech Intelligibility noise induced Hearing Loss OTOTOXICITY Schwan’s Cells Ablation
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氧化损伤与噪声性听力损失 被引量:1
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作者 李泽文 龚树生 +1 位作者 曾旭东 杨志敏 《国际耳鼻咽喉头颈外科杂志》 2008年第6期341-344,共4页
噪声性聋是一种常见的职业病,随着人们对该疾病认识的逐渐深入,针对其发病机制也提出了不同的防治方法。现就目前已得到大多数学者认同的氧化损伤机制及针对该机制的一些防治措施做一综述。
关键词 听力丧失 噪声性(Hearing Loss noiseinduced) 活性氧(Reactive Oxygen Species)
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噪声性聋的易感性与CDH23基因 被引量:1
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作者 郭晓民 薛希均 戴朴 《国际耳鼻咽喉头颈外科杂志》 2007年第6期331-333,共3页
噪声性聋(noise induced hearing loss,NIHL)存在个体的易感性差异,是一种不可逆但可预防的听力损害。强噪声暴露可导致内耳感觉毛细胞上的静纤毛损害,而 CDH23对维持静纤毛束的正常组织形态起重要的作用,是第一个被证实可引起人类耳聋... 噪声性聋(noise induced hearing loss,NIHL)存在个体的易感性差异,是一种不可逆但可预防的听力损害。强噪声暴露可导致内耳感觉毛细胞上的静纤毛损害,而 CDH23对维持静纤毛束的正常组织形态起重要的作用,是第一个被证实可引起人类耳聋且与噪声性聋易感性有关的基因。编码钙黏蛋白23的 CDH23基因的突变可引起噪声性聋及老年性聋。 展开更多
关键词 基因(Gene) 钙黏蛋白类(Cadherins) 听觉丧失 噪声性(Hearing Loss noiseinduced)
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Effect of Cavities inside Tube Banks on Acoustic Resonance
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作者 Hiromitsu HAMAKAWA Hidenobu MIYAGI Eiichi NISHIDA 《Journal of Thermal Science》 SCIE EI CAS CSCD 2010年第1期67-71,共5页
In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured the sound pressure level... In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured the sound pressure level, the amplitude and the phase delay of acoustic pressures and the gap velocity. As a result, we found many peak frequencies of sound pressure level with different Strouhal numbers, mainly about S1=0.15, 0.26 and 0.52. The variation of SPL for S,=0.26, 0.52 components in the tube banks with cavities was the same as the result of no cavities. The existence of cavities inside in-line tube banks caused the resonance of St=0.15. And the acoustic resonance of the first mode in the transverse direction was generated if the small cavities existed inside the tube banks. This resonance was not generated from the tube banks of no cavities. The resonance onset velocity in the transverse mode was fairly slower than that of no cavities. It was easy to generate acoustic resonance when there were small cavities inside in-line tube banks. 展开更多
关键词 Acoustic Resonance Flow induced noise In-line Tube Banks Cavity BOILER
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