50 results
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2. 住宅種別ごとの道路交通騒音に対する住民反応への 曝露量と非音響要因の影響
- Author
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古味 由惟, 横島 潤紀, 森長 誠, 辻村 壮平, 山内 勝也, 白橋 良宏, and 山崎 徹
- Abstract
This paper focused on the effects of non-acoustic factors on community response, namely annoyance and activity disturbances due to road traffic noise. Most of previous surveys in Japan addressed community response to noise for detached houses rather than that for apartments. However, it is likely that the above-mentioned community response differed by sound insulation performance between detached houses and apartments. Using a social survey conducted in areas facing arterial roads in 2019 and 2020, we applied the micro data to cross-tabulation and logistic regression analysis. Calculating phi coefficient and odds ratio, we discussed the difference by housing types. [ABSTRACT FROM AUTHOR]
- Published
- 2023
3. ロードノイズ低減のための機械学習による車両各部の目標特性決定手法―広帯域の周波数特性を決定可能な機械学習モデルの構築―
- Author
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市川 佳, 堤 純, 島村 島村, 立岡 宏治, and 海老澤 弘道
- Abstract
Determining the target characteristics of vehicle components for the road noise requires much development effort because component's characteristics are set through trial and error utilizing actual vehicles and FEMs. The purpose of this study is to construct a method that can determine the target characteristics without making a vehicle that achieves the target performance, in order to reduce the study time of road noise. This study focuses on drive point inertance. This paper investigates a method of constructing a machine learning model that can determine the target value of the wideband frequency response. [ABSTRACT FROM AUTHOR]
- Published
- 2024
4. ユニットモードを利用した伝達経路分析.
- Author
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望月 隆史, 鈴木 寛之, 日高 一希, and 花島 萌
- Abstract
First of all, the definition of “Unit Mode” is a smallest unit component mode which has only one loop and cannot be decomposed any further. The resonance frequency of an unit mode is almost the same as that of whole system. An unit mode is a disassembly of eigenmodes of each part, and eigenmodes are obtained by assembling the unit modes. The energy correlated with the response of interest on unit modal coordinates is called “Power Flow”. By visualizing this, it is possible to draw a mode path diagram that shows vibration transmissions from the excitation point to the evaluation point. The path can be changed by shifting the eigenvalues. This paper introduces the concept of power flow and its application to vibration transmitted through the vehicle body. [ABSTRACT FROM AUTHOR]
- Published
- 2024
5. 新型空冷ドライポンプNeoDry-G series の開発.
- Author
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松本知也
- Abstract
Quietness has become one of the key performance requirements for many users of vacuum pumps. In responcse, we launched the new air-cooled dry pump 'NeoDry-G' series in 2022. 'NeoDry-G' series is significantly quieter than its predecessor, the 'NeoDry-E' series. This paper provides a brief introduction to the NeoDry-G series, detailing how the quietness was improved and how it was evaluated. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
6. Construction of Vehicle Sound Model for Predicting Road Traffic Noise.
- Author
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Ryo Iwamoto, Yoshihiro Shirahashi, Masayuki Wada, and Toru Yamazaki
- Abstract
Road traffic noise is one of the most important issues. A more accurate prediction model is necessary to incorporate measures for reducing this noise. Current simulation models like the ASJ-RTN utilize fixed vehicle sound models. To enhance accuracy, an updated vehicle sound model, is recommended. This paper proposes a method for creating vehicle sound models with minimal measurements, applicable to all vehicle categories. Additionally, it presents a case study comparing the impact on exterior noise of a 100% electric drive hybrid system vehicle and an ICE vehicle, using the sound model developed through this method. [ABSTRACT FROM AUTHOR]
- Published
- 2024
7. リーフ式サスペンションの振動特性制御によるリヤデフうなり音低減技術
- Author
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小鍜治 純, 駒田 匡史, 佐藤 秀雄, 玉理 順造, 鈴木 浩司, and 杉山 平
- Abstract
In recent years, commercial vehicles with leaf suspension has been demanded to be as quiet as passenger vehicles. Therefore, rear differential gear whine noise also should be reduced and not to be stick out from interior back ground noise. It is known that the gear whine noise is strongly influenced by resonance of leaf suspension and the resonance frequency varies widely. This paper reports control method of the vibration characteristics of leaf suspension by changing the contact position and stiffness between each leaf, which is the main factor of variation. Using this method, gear whine noise could be decreased effectively. [ABSTRACT FROM AUTHOR]
- Published
- 2023
8. 幹線道路を取り巻く環境に関する住民意識の調査.
- Author
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古味 由惟, 横島 潤紀, 辻村 壮平, 梅﨑 良樹, and 山崎 徹
- Abstract
In recent years, the achievement of the environmental quality standards in areas facing roads has been improved. On the other hand, many residents along arterial roads are still annoyed by road traffic noise. In this paper, focusing on roadside environments of arterial roads, we try to develop a hierarchical evaluation structure model of dissatisfaction with the roadside environments based on the answers to open-ended questions of residents themselves. By deciphering the evaluation structure model, we can clarify the reasons for the dissatisfaction with road traffic noise and measures to resolve them and comprehend the position of road traffic noise in roadside environments. [ABSTRACT FROM AUTHOR]
- Published
- 2023
9. 分割計測の実稼働データを用いたロードノイズに対する 高寄与ボデーモード抽出
- Author
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荒井 雄理, 中塚 美穂, 駒田 匡史, and 吉田 準史
- Abstract
To reduce road noise effectively, focusing on high contributing principal component (PC) modes is a well known method. Although, the difficulty of simultaneous measurement when applied to actual vehicle test is one of the issues. Therefore, a method was proposed to obtain the whole body PC modes by integrating the partial PC modes. In this paper we applied this method to an operational test data for each measurement group and obtained the whole body PC modes, the effectiveness of the proposed method for practical usage was proved. [ABSTRACT FROM AUTHOR]
- Published
- 2022
10. エネルギー最適制御理論を適用した新機構アクティブサスペンションの性能・ --理想アクチュエータを用いた基本性能の把握一
- Author
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福島直人 and 芝端康二
- Abstract
This paper introduces a new active suspension system and discusses the application of the energy optimal control theory. In this new suspension system, an actuator and a damper are arranged in series. Thanks to this new design, the suspension system without an additional mass consists of an active mass-damper system. Applying the energy optimal control theory, it is shown by-the computer simulations that the riding comfort can be improved over wide range of frequency including the resonance frequency of the unsprung mass. The results show that the vibration of the sprung mass is reduced to a level which is lower than that of a Shinkansen car without causing an increase in the vibration of the unsprung mass. Additionally, the control law is interpreted and the mechanism behind the decrease in the vibration of the sprung mass is analyzed. [ABSTRACT FROM AUTHOR]
- Published
- 2022
11. 副室ジェット燃焼エンジンの高周波燃焼騒音発生メカニズム解析(第3 報) -ジェット火炎による燃焼室共鳴励起メカニズムの解析-
- Author
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鳥居 建史, 新谷 祐輔, 木村 範孝, 小林 広樹, and 小西 敬三
- Abstract
This paper compares the characteristics of in-cylinder pressure measured in actual engines for various combustion modes and the characteristics of flame distribution and fuel reaction rate due to flame propagation calculated by CFD for those same modes, based on previous research. Results show that the significant increase in high-frequency in-cylinder pressure oscillation in pre-chamber jet combustion is due to two factors: a high in-cylinder pressure rise rate that is 2 to 3 times higher than in conventional spark ignition combustion, and an asymmetrical flame distribution caused by differences in fuel reaction rate of jet flames ejected from multiple nozzles of the pre-chamber. [ABSTRACT FROM AUTHOR]
- Published
- 2023
12. 副室ジェット燃焼エンジンの高周波燃焼騒音発生メカニズム解析(第2 報) -燃焼室共鳴周波数帯の筒内圧力振動の評価法-
- Author
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小西 敬三, 鳥居 建史, 木村 範孝, 小林 広樹, and 岡田 大輔
- Abstract
In this paper, an evaluation method for in-cylinder pressure oscillation is developed to quantitatively determine the magnitude of combustion noise in the 7-10 kHz band characteristic of pre-chamber jet combustion engines. In this method, in-cylinder pressure is measured for 400 cycles of crank angle history, and peak-to-peak amplitudes of pressure oscillations in the combustion chamber resonance band are obtained for cycleby-cycle using a bandpass filter. The peak-to-peak amplitudes are then averaged to obtain an evaluation indicator for in-cylinder pressure oscillation that enables an indirect evaluation of high-frequency combustion noise without measuring engine radiation noise. The results showed that the evaluation indicator in pre-chamber jet combustion is 16 times higher than that of conventional spark-ignited combustion, which can be evaluated at a single fixed in-cylinder pressure sensor. [ABSTRACT FROM AUTHOR]
- Published
- 2023
13. 骨格パネル間の点結合部における振動エネルギー伝搬メカニズム.
- Author
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阿部 啓介 and 山崎 徹
- Abstract
This paper analyzes the mechanism of vibrational energy propagation and panel vibration generation at the point joints between frame and panel which can be applied to reduce the noise. First, it is shown that the transmitted power at point joints that contribute to the panel vibration is caused by the out-of-plane component in relation to the frame deformation, and the evaluation of the out-of-plane transmitted power makes it possible to identify the effective site for reducing the panel vibration. Next, the relationship between the energy inflow to the panel and the panel vibration during the initial propagation of the traveling wave was numerically verified, and a panel vibration reduction method was proposed by suppressing the energy propagation to the panel. [ABSTRACT FROM AUTHOR]
- Published
- 2023
14. 操舵応答の振動現象のエネルギー伝達特性による記述.
- Author
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黒川 明仁, 山崎 徹, 岩田 和朗, 栗原 海, 川越 雅典, and 中村 幸宣
- Abstract
This paper describes the vibration phenomenon on vehicle motion from the perspective of energy propagation based on a two-degree-of-freedom vibration system. The energy transmissibility between the yaw and roll motions is analytically formulated by using their uncoupled natural angular frequencies, damping, and coupling characteristics. It is shown that the neutral steering character can be expressed by zero-energy transfer between the yaw and roll motion. The transmissibility is also useful to express the transient performance of the vehicle with under/over steering characteristics and the stable limit speed and so on. Finally, it is demonstrated that the transmissibility is useful to understand the transient performance under changing the roll stiffness and damping coefficient as examples. [ABSTRACT FROM AUTHOR]
- Published
- 2023
15. [Immission Assessments of Wind Turbine Noise in Residential Areas around Wind Farms].
- Author
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Fukushima A
- Subjects
- Environmental Exposure analysis, Environmental Exposure standards, Humans, Japan, Environment, Environmental Exposure adverse effects, Noise adverse effects, Power Plants, Wind
- Abstract
Since the large-scale construction of wind power facilities in Japan, serious complaints have arisen from residents regarding wind turbine noise (WTN). However, there was insufficient scientific background to assess this issue. To address this situation, several research projects have been conducted by the Ministry of the Environment, Government of Japan. In this paper, we report actual WTN field measurements for these projects. The L
Aeq values of WTN ranged from 25 to 50 dB in residential areas. On the other hand, the residual noise levels in control areas with similar local characteristics to the wind farm areas but not affected by WTN ranged from 20 to 35 dB. Thus, there was a notable difference between WTN and residual noise. Wind power facilities are often constructed in quiet, rural districts. With regards to WTN, LAeq of noise caused by wind turbines as well as the increase in the overall noise level are important. The measurements of spectral characteristics of WTN were compared against the criterion curve to assess low-frequency noise. As a result, infrasound (frequency components below 20 Hz) for all measured WTN values in the residential (immission) areas were found to be much lower than the corresponding values on the criterion curve. In addition, amplitude modulation (AM) sound (also referred to as "swish sound") is often associated with WTN, and can cause serious discomfort to nearby residents. The actual situation with regard to AM sound in residential areas located near wind farms was clarified by field measurements.- Published
- 2018
- Full Text
- View/download PDF
16. Influences of low-frequency and other noises produced by wind turbines: An epidemiological literature review.
- Author
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Kubo T, Hasunuma H, Morimatsu Y, Fujino Y, Hara K, and Ishitake T
- Subjects
- Health Status, Sleep Wake Disorders epidemiology, Stress, Physiological, Noise, Wind
- Abstract
Objectives Due to its' environment-friendly and clean energy characteristics, wind power has been increasingly used globally, particularly in advanced countries. However, concerns about health hazards, especially due to low-frequency and other noises generated from wind turbines, have been reported repeatedly. In order to manage adverse health effects appropriately, regulatory standards or guidelines that consider the health of residents need to be developed. To provide a scientific basis for the development of such regulatory standards and guidelines, this paper conducted a literature review to analyze epidemiological studies involving residents living in the vicinity of wind farms.Methods Using the PubMED database, epidemiological papers that examined the health effects of noises produced by wind turbines were searched and collected. Additional papers were collected from the abstracts presented at relevant international academic conferences such as the Inter-Noise 2013 and Wind Turbine Noise 2015. An evidence table comprising the study design, subjects, exposure assessment, outcomes, confounders, and research results of each selected study was created.Results A total of 11 papers were collected (2 of which were abstracts from the international academic conferences). These studies reported outcomes such as perception of noises, annoyance caused by the noises, and the association of the noises with stress and sleeplessness. Significant associations between the noises or annoyance produced by wind turbines and subjective adverse health effects were reported repeatedly. Two studies reported an odds ratio of 1.1 for an increase of 1 dB in the A-weighted sound pressure level as a factor representing the influence level. For other factors, it was not possible to compare the magnitude of the impact among the collected studies. Individual attitudes toward wind power and landscapes, economic benefits of wind farms, visibility of wind turbines, sensitivity to sounds, and concerns over health hazards were reported as confounders.Conclusion Significant associations between the noises or annoyance produced by wind turbines and subjective adverse health effects were reported repeatedly. However, there was insufficient evidence to conclude whether the annoyance was caused by the psychological response to the construction of wind farms or by the actual exposure to noises generated by wind farms.
- Published
- 2017
- Full Text
- View/download PDF
17. インピーダンスマッチングを活用したガラス透過音の低減技術.
- Author
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上山さぎり, 若原正明, 鴫原孝佳, 駒田匡史, 野尻昌利, and 山田宜伸
- Abstract
In order to improve wind noise in high frequency range above 2kHz, this paper proposes a new technique focusing on high damping glass-run to reduce glass transmission noise due to coincidence effect at low cost. The technique is characterized by controlling energy transmission by utilizing impedance matching between glass and glass-run without changing materials. [ABSTRACT FROM AUTHOR]
- Published
- 2022
18. 固有振動数成分除去法による マルチロータ型ドローンの吊り荷の制振.
- Author
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栗原 海, 山崎 徹, and 岩田 和朗
- Abstract
When a drone is used to suspend and transport a load, the residual vibration that occurs when the drone stops is a problem. In this report, residual vibration is suppressed by elimination of the natural frequency component from the apparent external force, which considers the effects of non-linearity and damping. Numerical simulations and experiments have verified the effectiveness of this method for a suspended load of a multi-rotor drone. [ABSTRACT FROM AUTHOR]
- Published
- 2024
19. Cascading design method using the relation between mutual mean compliance and frequency response function based sub-structuring
- Author
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Yuichi MATSUMURA, Hirotaka SHIOZAKI, Tsukasa OHZAWA, and Kohei FURUYA
- Subjects
cascading design method ,substructuring ,mutual mean compliance ,modal analysis ,noise ,vibration ,harshness ,frequency response function ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
This paper addresses the cascading design method of NVH (Noise, Vibration and Harshness) performance between an OEM (Original Equipment Manufacturer) and suppliers. The increasing trend toward electric vehicles requires the exploring of cascading design method, because of the easiness of the assembly of the electric vehicles. However, there are difficulties for the cascading design of NVH performance to overcome the coupling problem among each subsystem. It is generally difficult to divide key evaluation characteristics of a whole structure to individual characteristics of each subsystem because of the coupling resonance. In this paper, cascading design method which utilizes the MMC (Mutual Mean Compliance) was proposed. The MMC is used as an index to meet the final NVH target levels of a whole structure. Then, the MMC is cascaded to each subsystem or component. Finally, the cascaded MMC is achieved by improving individual MMCs of each separate subsystem, while being careful about the resonance of a whole structure caused by strong coupling. In the paper, it is shown that the recalculation of MMCs after subsystem’s structural modification is feasible using FBS (Frequency response function Based Sub-structuring). In addition, MMC based cascading design method using FBS was defined and organized as a procedure. The method was also verified by a numerical case study.
- Published
- 2019
- Full Text
- View/download PDF
20. 船外機音質向上のための指標研究.
- Author
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村松 秀太, 小橋 保方, and 直江 学
- Abstract
The outboard motor market is expanding due to an increase in leisure use, and there is a demand for enhanced quietness and comfort of outboard motors. In the development of automobiles and motorcycles, original sound quality index research and sound quality development are being pursued to enhanced product value, but in the development of outboard motors, there are examples of noise reduction and compliance with noise regulations, but there are almost no examples of sound quality enhancement. In this study, we focused on the sound quality of outboard motors and conducted a questionnaire survey of North American boat users using the SD method. The difference in the impression of outboard motor sound quality was clarified, and factors affecting the results were obtained by factor analysis, and three important factors for sound quality of outboard motor could be extracted. In addition, considered the physical features of the extracted factors. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
21. Component mode synthesis with residual stiffness for brake squeal complex eigenvalue problem
- Author
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Kohei FURUYA, Kohei SHINTANI, and Satoshi ITO
- Subjects
self-excited vibration ,noise ,complex eigenvalue analysis ,component mode synthesis ,disk brake squeal ,finite element method ,residual stiffness ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
This paper discusses component mode synthesis (CMS) to solve the complex eigenvalue problem that expresses the disk brake squeal equation. The disk brake squeal is known as self-excited vibration; the real and imaginary parts of the complex eigenvalue indicate the damping coefficient and natural angular frequency, respectively. The modes that have a negative damping coefficient cause disk brake squeal. Therefore, calculating the eigenpairs (eigenvalues and eigenmodes) with accuracy is important. To solve the complex eigenvalue problem, a direct solver, such as the Hessenberg method, and an iterative solver, such as the Lanczos method, are used. By using a direct solver, all eigenpairs can be calculated with high accuracy, but the computational cost is large. Consequently, its application is limited to small DOF problems of approximately 10,000 DOF. On the other hand, calculating the eigenpairs of large DOF problems by using an iterative solver is possible; this also has disadvantages, such as missing actual modes and accepting quasi-modes. To overcome these disadvantages, a CMS that uses both a direct solver and an iterative solver is used. By using CMS, avoiding the disadvantages of missing actual modes and accepting quasi-modes while still using fewer computer resources than the direct solver alone is possible. However, the calculated eigenpairs contain computational error caused by CMS. In this paper, to improve the accuracy of CMS, a novel CMS method adapting residual stiffness is proposed. Here, novel CMS is formulated, and the advantage it offers is shown by applying the direct solver, the previous CMS, and the novel CMS to the finite element models of a disk brake.
- Published
- 2014
- Full Text
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22. Modal energy propagation method in coupled systems of rigid and flexible structure
- Author
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Koki YAMASHITA, Akinori UTSUNOMIYA, and Iwao HONDA
- Subjects
noise ,vibration ,modal analysis ,structure-borne sound ,component mode synthesis ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
Since the noise generated by mechanical structures affects the merchantability, it is important to predict it at the design stage. Statistical energy analysis (SEA), which solves the energy equilibrium equation between subsystems, is widely used to predict structural noise. However, due to the assumption that eigenmodes are treated statistically, SEA is limited to application in the high-frequency range with high mode density, so it is the challenge to develop vibration power flow analysis method for the low- and mid-frequency range. In this study, we propose a modal energy propagation analysis method to evaluate the vibration power flow between the eigenmodes of a subsystem. In this paper, the validity of the theory and the countermeasures to reduce the vibration by controlling the transmitted power between the eigenmodes are verified using a simple test apparatus. As a result, it was shown that the transmitted power between subsystems can be approximated by the summation of the transmitted powers of individual eigenmodes, confirming the validity of the calculation theory. In addition, it was confirmed that the mean square velocity of the subsystem can be reduced by identifying and controlling the transmitted power of individual eigenmodes using this method.
- Published
- 2022
- Full Text
- View/download PDF
23. Jumping Behavior of Heald in a Shedding Motion of Loom.
- Author
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Taketo, Akamura, Toshiyasu, Kinari, Tomotsugu, Shimokawa, Daisuke, Miyashita, Yoshikazu, Mochizuki, and Sukenori, Shintaku
- Abstract
Noise in weaving mills has become very serious problem with increasing speed of weaving machine in recent years. One of these sources of noise is the collision sound of healds caused by shedding motion. It was clarified in our previous paper that the collision sound of healds is significantly connected with motion of heald during a period of shedding motion. In this research, therefore, photographs of the behavior of heald in a shedding period were taken by using a high-speed-camera system on a model shedding device. At the same time, noise was measured to investigate the collision sound of healds. Collision between healds and heald bar caused by heald jumping and the collision of healds were observed. It was confirmed that noise is the largest at the both collision timings. On the other hand, it has been already understood that the tension of warp yarn significantly affects the behavior of heald. It was also observed that the collision of heald and heald bar was delayed or eliminated with increasing tension of warp yarn by photographic observation. At the same time, noise was decreased with increasing warp tension. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
24. Average vibration reduction effect in low frequency band by initial design using analytical SEA
- Author
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Kazumasa IKEDA and Toru YAMAZAKI
- Subjects
noise ,vibration ,initial design ,asea ,fem ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
In the automobile industry, quietness has been pursued with electrification and vehicle weight has been reduced for longer traveling distance. In design of component products to be mounted on vehicles, “low noise” and “weight reduction” have been also required. In order to realize them, it is important to approach sound characteristics in initial design stage and detail design stage. In the initial design stage, parts layout, material and rough dimensions are designed to decrease “average” of noise level. In the detail design stage, accurate dimensions and detailed shapes are designed to suppress noise peaks. These are called “two-step design”. Especially, analytical SEA (ASEA) is a suitable technology for the initial design because it provides results by using only theoretical equations without 3-D models. However, it has hurdles to be a practical process. One is a constraint of ASEA that accuracy of results can be kept high only in high frequency range. In this paper, we proved theoretically and practically that initial design using ASEA was effective even in low frequency range.
- Published
- 2020
- Full Text
- View/download PDF
25. Extension of experimental statistical energy analysis to structural vibration with low modal density
- Author
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Kazumasa IKEDA and Toru YAMAZAKI
- Subjects
noise ,vibration ,sea ,measurement ,modal density ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
Statistical energy analysis (SEA) is a method for understanding energy transfer paths related to vibration noise generation. In SEA, a target object is separated virtually into subsystems among which the transfer of vibration energy can be quantified. Conventionally, SEA is applied to structures that comprise thin plates, such as the bodies of large ships. The structure is then designed so that the transfer of vibration energy is varied to avoid energy being concentrated on any one subsystem. Although SEA is an effective method for preventing vibration noise problems, it becomes critically inaccurate when applied to structures with low modal density. This paper is aimed at clarifying an appropriate measuring process for constructing SEA models with two subsystems that provides high accuracy for structures with arbitrary modal densities. Evaluations of three simplified structures with different modal densities are conducted to determine how to improve the conventional measurement method.
- Published
- 2019
- Full Text
- View/download PDF
26. Development of double nearfield acoustic holography method (Basic experimental results)
- Author
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Masao NAGAMATSU
- Subjects
acoustic holography ,sound localization ,acoustics ,noise ,low frequency ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
There are several types of sound localization methods. In middle frequency around 1kHz, these methods are effective to detect the sound source location. However, for low frequency sound under 100Hz, almost sound localization methods do not have enough resolution to detect the sound source location. To overcome this problem, the author is now developing a new sound localization method, "Double Near-field Acoustic Holography method." This method is converted method of conventional Near-field Acoustic Holography method. The Near-field Acoustic Holography method has best resolution in all sound localization method. However, for low frequency sound sources lower than 100Hz, this method does not have enough resolution to detect the its position. The proposed Double Near-field Acoustic holography method is developed to improve the resolution of low frequency sound localization. In this paper, the experimental results with small speaker are reported. By these experiments, it is probed that the proposed Double Near-field Acoustic holography method has enough resolution to detect the position of the low frequency sound source.
- Published
- 2019
- Full Text
- View/download PDF
27. Noise increase phenomenon of the air flow through a perforated metal plate
- Author
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Hiroki MATSUMOTO, Sou IGARASHI, and Masaki UMINO
- Subjects
aerodynamic sound ,perforated metal plate ,air flow ,lock-in ,coherent output power ,noise ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
The aerodynamic noise generated from a perforated metal plate varied by air-flow direction. In the case of expansion type perforated metal plate, it generates very large level aerodynamic noise with a prominent peak in the frequency characteristic. In this paper, velocity fluctuation at some measuring points is measured by a hotwire anemometer to examine its cause. In the experiment, coherent output power (COP) of velocity fluctuation is calculated. The coherence function is defined by the relations between the generated noise and velocity fluctuation of air flow behind perforated metal plate. The expansion type perforated metal plate generates orderly vortex shedding and it brings the vibration of perforated metal plate. The distribution of partial overall value of COP indicates strong correlation with the plate vibration mode. That phenomenon is predicted as lock-in phenomenon between vortex and vibration of the plate.
- Published
- 2019
- Full Text
- View/download PDF
28. 音響的ソフト境界を有する消音器の広帯域化と縮小化及びその応用に関する研究
- Author
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Fujiwara, Kyoji and 藤原, 恭司
- Subjects
sound ,ダクト ,noise ,騒音 ,消音器 ,ソフトダクト ,duct ,soft duct ,音響 ,silencer - Abstract
本論文は,ダクト騒音の低周波数域において良好な低減性能を持つ,ダクト断面周囲の音響特性がソフトである消音器について検討するものである。 音響的にソフトな境界とは,表面の吸音率が0複素反射率が-1というもので,境界面での音圧が零となる,音響的に剛な境界の対極をなすものである。理想的なソフト境界を有するダクトでは,入射する平面波は完全反射され,下流側へ騒音が伝搬しないため,騒音制御にソフト境界を導入することで良好な効果を得られることが期待される。「理想的」とするのは,一般的な材質で定義通りの条件を満たすものが存在しないからであるが,対象周波数の1/4波長となる音響管を配列することで近似的に実現される。 1/4波長音響管を騒音制御に用いた検討はこれまでに幾つか行われてきている。ダクトへの適用に関する基礎的な研究としては,音響管の幅や配列寸法と得られる効果の関係について調べられている。しかし,減音効果と密接な関係があるダクトの幅と効果の関係について検討が為されていない。 また,1/4波長音響管は,その機構が故に減音性能が周波数依存することが避けられない。そのため,広帯域化に関する応用的研究が行われており,異なる設計周波数の音響管を組み合わせる場合について検討されており,一定の成果を得ている。しかし,その際に組み合わせるべき設計周波数に関する指標を示すまでに至っておらず,実用的な設計に向けては検討の余地が多く残されている。 なお,ソフトダクトは低周波数域において良好な成果が得られるが,制御対象周波数が低くなるに従って必要となる音響管の寸法も大きくなる。この問題について,ダクトスペースを縮小化させるための検討が行われており,音響管開口端に薄膜を付加したり,音響管にヘルムホルツ共鳴器を組み込むことに関する検討が行われている。しかし,これらの方法は,減音効果が小さくなったり効果の得られる帯域が狭くなったりするなどといった二次的な問題を生じており,縮小化に関しても多くの課題が残る。 防音壁への応用についても検討されているが,基となるべきソフトダクトにおける広帯域化や縮小化の検討に課題が残されていることもあり,開口部へのソフトダクト適用方法について有用なアイデアが出されたものの,実用に向けては多くの課題が残されている。 本論文では,これらの既往の研究に関する課題点を整理した上で,ソフトダクトの減音性能に関して,ソフトダクトを構成する寸法と得られる効果についてダクト幅をパラメータに含めた体系的な整理を行うことや,基本形状及び広帯域化のための配列について設計指針の策定を目的とした。また,ソフトダクトの縮小化に関して,効果の得られる帯域幅が制限されないような新しい形状を提案して縮小化を図ると共に,提案した音響管を用いてソフトダクトの広帯域化についても検討する。また,ソフトダクトの広帯域化と縮小化について得られた知見を基に,ダクト以外の騒音対策への適用について実用的な対策案を提案することを目的とする。 まず,ソフトダクトを構成する各部寸法と効果の関係について整理した結果,ダクトの幅が遮断周波数決定要因となる重要な知見を得て,その遮断周波数と音響管の設計周波数の関係により得られる周波数特性が大きく影響されることを示した。また,設計周波数の波長に対するソフトダクト各部寸法を一定の比率として,異なる設計周波数の音響管を組み合わせた場合,組み合わせる設計周波数が概ね明示的に得られることになるため,設計が容易になることを示した。更に,設計周波数を連続的に変化させた場合に得られる効果について数値計算による検討を行ったところ,設計周波数のシフト幅と設計周波数の波長に対するダクト幅の比の逆数を掛け合わせたパラメータと非常によい相関関係にあることを明らかにし,広帯域化設計の指標となるものを導き出すことができた。 次に,ソフトダクトの縮小化について検討を行った。本論文では,縮小化によって帯域が制限されないような形状として,音響管の側面を傾斜させる新たな形状を提案した。この形状により,体積を一定にした状態で減音効果をより低周波数域へシフトさせることが可能であることや,体積を一定にした状態で減音効果を低域にも高域にもシフトさせることが出来ることを示した。また,音響管寸法変化では説明できない周波数シフトの理由について,円筒進行波の解析から説明した。更に,側面の傾斜タイプが異なる音響管を組み合わせることでソフトダクトユニットの縮小化や広帯域化が可能であることを示した。 最後に,上記で得た知見を基に,防音壁開口部への適用について検討した。広帯域騒音である新幹線騒音を対象にした検討では,それまでに検討してきた広帯域化の音響管ユニットを適用しても有意な効果は得られなかった。しかし,特定の周波数が卓越する変圧器を対象とした検討では,開口部へソフトダクトを配列した場合に得られる効果が,開口部のない同じ高さの単純障壁と同じとなり,防音壁に開口が設けられた場合であってもソフトダクトを用いた騒音制御が非常に有効であることを示した。, This paper studies a silencer with a soft acoustic feature of the circumference of a duct section which has good reduction performance at low frequencies of duct noise. In addition, since it is unrealizable with a general material, the soft surface is realized by approximation using quarter-wavelength sound tubes. Some study using quarter-wavelength sound tubes for noise control has been carried out until now. But many problems are also left behind. So, in this paper, a problem is adjusted about conventional study. It aimed at leading a design manual about the arrangement for a bloadbanding, and the miniaturization of the soft duct was studied by suggesting the new shape. Furthermore, the application except for a duct was also considered based on the knowledge acquired about the bloadbanding and miniaturization of the soft duct. As a result of adjusting about each part size which constitutes a soft duct and the relation of the noise reduction effect, it turned out that the width of a duct becomes an important factor which determines cutoff frequency. Since the rough design frequency to combine would be taken in advance when the sound tube of different design frequency setting the size which constitutes a soft duct to the wavelength of design frequency as a fixed ratio is combined, it became clear that a design becomes easy. Furthermore, the effect acquired when varying design frequency continuously was studied. As a result, it becomes clear that it is in very good correlation about the parameter which consists of the ratio of duct width and the shift width of design frequency to the wavelength of design frequency, and the design manual for a bloadbanding was able to be drawn. About the miniaturization of the soft duct, the new shape which made the side plate of the sound tube incline was suggested. It becomes possible to shift the noise reduction effect of it to the low frequency, where volume is fixed. Moreover, it is possible to shift the noise reduction effect to both low frequency and high frequency depending on the inclination pattern of a sound tub side plate. And it was shown by combining the sound tub from which the inclination type of a side plate differs that the miniaturization and bloadbanding of a soft duct unit are possible. Finally, application to the sound barrier which has an opening was considered based on the knowledge acquired above. In the study for the transformer in which specific frequency surpasses, the effect acquired when a soft duct is arranged to an opening became the same as the simple barrier of the same height without an opening. Even if it was a sound barrier which has an opening, it was shown that the noise control using a soft duct is very effective.
- Published
- 2010
29. Modal damping ratios of the two-degree-of-freedom acoustic model having a Helmholtz resonator
- Author
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Shinichi MARUYAMA, Seiji TSUTSUMI, and Takashi YAMAMOTO
- Subjects
acoustic ,sound field control ,resonance ,noise ,damping ,dynamic absorber ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
Helmholtz resonators are used in many industrial products as devices for reducing low-frequency noise. An advantage of the Helmholtz resonator is that the structure is simple and applicable to low-frequency noise for its size. Further, an important feature is that the development costs and product costs are relatively low in actual product development. The optimum combination of the natural frequency and modal damping ratio of a Helmholtz resonator is dependent on the characteristic of the noise source. It is selected so as to minimize the sound pressure levels when the noise is stationary. In the case of a transient noise problem, the natural frequency and modal damping ratio is tuned for maximizing the modal damping ratios of the system consisting of the main system and a Helmholtz resonator. Noise reduction effects of Helmholtz resonators are generally predicted by 3D acoustic analysis. Recently, the effects are estimated by CFD at higher sound pressure levels exceeding 100dB, because they are greatly affected by eddies generated in the neck portion of resonators. However, there is no suitable method to predict the noise reduction effects of Helmholtz resonators that engineers can use easily in the early stages of design. This paper describes a simple method for estimating the optimum value of modal damping ratios of the acoustic system having a Helmholtz resonator. Here, two-degrees-of-freedom models similar to the mass-spring-damper models used in the design of tuned mass dampers are used. In addition, the differences between the optimum conditions of tuned mass dampers and Helmholtz resonators are described.
- Published
- 2016
- Full Text
- View/download PDF
30. DEVELOPMENT OF REAL-TIME VOICE PROCESSING SYSTEM FOR THE LOUDSPEAKERS USED UNDER NOISY ENVIRONMENTS
- Subjects
noise ,loudspeakers ,voice ,speech processing - Abstract
Age related deterioration of hearing make elder persons difficult to listen human voices especially under noisy environments like train stations. The aim of this study is to develop a speech pre-processing system used for public address systems used under noisy environments. The proposed system is based on multi channel compression, and the compression levels are function of surrounding noises. Furthermore the system includes amplitude adjustments to keep the output power of the public address system unchanged, in comparison with the system without the proposed system, to avoid bothering young persons. The validity of this concept was confirmed in previous work. The experimental system used for the work can not process speech in real-time, however. This paper deals with modifications applied to the system to enable real-time processing. Furthermore, the experiments conducted on subjects using the proposed system and their results are also discussed. The objective results did not show effectiveness of the system statistically. On the other hand, the subjective ones statistically showed the effectiveness regarding intelligibility. Therefore, the objective effectiveness may become statistically significant as the number of subjects increases.
- Published
- 2021
31. ECG Cycle Recognition
- Subjects
noise ,fuzzy inference ,ファジィ推論 ,ECG ,pattern recognition ,1周期の検出 ,パターン認識 ,ノイズ ,cycle detection ,心電図 - Abstract
本論文では,心電図波形の1周期を認識する方法について述べる。従来の認識システムでは,波形の個人的,時間的変化やノイズを多く含む場合に対処できていない。ここでは,心電図データをある程度確からしさが保証されたあいまいなデータとして扱い,従来の認識システムの問題点に対処した。波形の特徴として傾斜に注目し,傾斜を一定区間内での相対的なファジイデータとして表現し,ファジィ推論を行うことで1周期を認識する。ファジィ推論により,ノイズや波形形状の変化に対処する認識を実現した。AHA(American Heart Association)の評価用心電図データを用いて実験した結果,88.7~99.8%,平均で96%の認識率を得た。, This paper describes a new approach for ECG cycle detection. The method in this paper is based on ECG cycle pattern recognition in fuzzy environment. For the purpose of diminishing noise interference, ECG signals are transformed into fuzzy data. The transform criteria are adjusted to follow the variance of ECG. The ECG cycle is recognized by fuzzy inference using the rule base. An overall 96% correct detection rate is obtained with the AHA (American Heart Association) database.
- Published
- 1990
32. Application of shape optimization to brake squeal phenomena
- Author
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Kohei SHINTANI, Kohei FURUYA, and Satoshi ITO
- Subjects
self-excited vibration ,noise ,complex eigenvalue analysis ,component mode synthesis ,disk brake squeal ,finite element method ,residual stiffness ,optimum design ,h1 gradient method ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
The present paper describes an application of non-parametric shape optimization to disc brake squeal phenomena. The disk brake squeal is known as self-excited vibration; the real and imaginary parts of the complex eigenvalue indicate the damping coefficient and natural angular frequency, respectively. The modes that have a negative damping coefficient cause disk brake squeal. Therefore, a main problem is defined as complex eigen value problem and a real part of the complex eigenvalue causing the brake squeal is chosen as an objective cost function for the shape optimization problem. For the solution to main problem which has a large number of DOF, component mode synthesis method adapting residual stiffness (CMS-R) is used in order to improve the accuracy of eigenpairs by conventional component mode synthesis method (CMS). The Fre´chet derivative of the objective cost function with respect to the domain variation, which we call the shape derivative of the objective cost function, is evaluated using the solution of the main problem and the adjoint problem. A scheme to solve the shape optimization problem is presented using an iterative algorithm based on the H1 gradient method for reshaping. For an application of the shape optimization method, a numerical example by using a practical disc brake model is presented. From the numerical result, the real part of the target complex eigenvalue monotonously decreases until it reach zero and effectiveness of CMS-R with regard to the shape optimization problem is presented.
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- 2015
- Full Text
- View/download PDF
33. Experimental study on vibration and noise characteristics of small fan motors
- Author
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Masaki OGUSHI, Koki SHIOHATA, Takako OTSUKA, Atsushi TARODA, Zhong YAN, Yoichi KAWAI, and Miyuki FURUYA
- Subjects
rotary machinery ,fan motor ,noise ,vibration of mechanism ,electromagnetic induced vibration ,natural frequency ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
In this paper, the phenomenon of vibration and noise in a small fan motor caused by electromagnetic forces were experimentally investigated. First, vibration characteristics of the fan motor in a non-operating state were determined by experimental modal analysis. Next, vibration and noise characteristics of the fan motor in an operating state were determined. The rotational speed was continuously decreased from 2200 r/min to 1200 r/min while the measurements were taken. A detailed frequency analysis was also performed to investigate the directional patterns of noise at the rotational speed which the significant resonance were confirmed. In addition, analysis on the vibration and noise of the fan motor after turning off its power were performed. As a result, it was found out that the significant vibration and noise were generated in the axial direction, and were resonance phenomena between harmonic frequency of electromagnetic force and natural frequency of the fan.
- Published
- 2014
- Full Text
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34. パンチングメタル板を通過する気流による騒音増大現象
- Author
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Hiroki Matsumoto, Sou Igarashi, and Masaki Umino
- Subjects
Materials science ,Aerodynamic sound ,Physics::Instrumentation and Detectors ,Lock-in ,Acoustics ,Airflow ,Coherent output power ,Air flow ,Perforated metal plate ,Physics::Fluid Dynamics ,Noise ,Perforated metal - Abstract
The aerodynamic noise generated from a perforated metal plate varied by air-flow direction. In the case of expansion type perforated metal plate, it generates very large level aerodynamic noise with a prominent peak in the frequency characteristic. In this paper, velocity fluctuation at some measuring points is measured by a hotwire anemometer to examine its cause. In the experiment, coherent output power (COP) of velocity fluctuation is calculated. The coherence function is defined by the relations between the generated noise and velocity fluctuation of air flow behind perforated metal plate. The expansion type perforated metal plate generates orderly vortex shedding and it brings the vibration of perforated metal plate. The distribution of partial overall value of COP indicates strong correlation with the plate vibration mode. That phenomenon is predicted as lock-in phenomenon between vortex and vibration of the plate.
- Published
- 2019
35. A new method to compute sound transmission loss by acoustic FEM
- Author
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Sachiko ISHIDA, Hiroaki MORIMURA, You GOTOU, and Ichiro HAGIWARA
- Subjects
sound insulation ,sound transmission loss ,noise ,acoustics ,sandwich panels ,finate element analysis ,origami ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
In this paper, a new method to evaluate performance of sound insulating plates in closed medium is investigated by using acoustic finite element method (FEM) under such two conditions that plates are having free ends and that plates are simply supported. The proposed method is able to compute sound transmission loss by using sound pressures at the small numbers of properly selected nodes considering acoustical symmetry of modal shapes in the closed medium, which is equivalent to the theoretical transmission loss without using all nodes existing in the medium. By the proposed method, the computed transmission loss does not depend on sizes or shapes of the medium; it is the unique transmission loss of the sound insulating plate itself. As sound insulating plates, the following three models are constructed; a single plate, double-leaf plates and the high-rigid sandwich panel called “trusscore panel”. It is also shown that sandwich trusscore panel works effectively at low frequency range since it is sufficiently rigid and that computed sound transmission loss of the trusscore panel has tendency as observed on a single plate having the equivalent weight and stiffness to the trusscore panel. Trusscore panels can be applied widely in industrial fields in the future such as walls or floors in a car, train or building to reduce interior noise.
- Published
- 2014
- Full Text
- View/download PDF
36. 小弦節比翼列ディフューザにおける二次流れの挙動解析 (第1報, 翼前縁位置の影響)
- Subjects
Diffuser performance secondary flow ,Centrifugal Blower ,Low solidity cascade diffuser ,Noise - Abstract
This paper deals with the effect of the blade leading edge location of low solidity cascade diffuser (LSD) on noise and diffuser performance in a centrifugal blower. The noise of the vaneless diffuser, varied little in a wide flow rate range, on the other hand, that of the LSD increased remarkably as the flow rate decreased. Two kinds of discrete frequency noise appeared due to interaction between the rotating jet-wake flow and the LSD blade and another interaction between the rotating impeller blades and the reverse flow toward the impeller exit, however, it was found that the LSD noise was mainly dominated by the broadband noise. By shifting the LSD blade leading edge location downstream from RLSD = 1.10 to 1.20, the noise was reduced by about 3 dB at maximum without deterioration of the diffuser performance. The mechanism being able to maintain the high pressure recovery was pursued in view point of formation of the recirculating secondary flow.
- Published
- 2010
37. Layout of Sound Absorbing Materials in 3D Rooms Using Damping Contributions with Eigenvectors as Weight Coefficients(Mechanical Systems)
- Subjects
Finite Element Method ,Noise ,Modal Strain and Kinetic ,Energy Method ,Damping ,Computer Aided Analysis ,Damping property - Abstract
This paper deals with analysis for layout of sound absorbing materials in three-dimensional rooms using damping contributions with eigenvectors as weight coefficients. Elements of absorbing materials are modeled by 3D finite element, which having complex density and complex volume elasticity. By expanding the solution of complex eigenvalue problem with small parameter, equations of motion are derived using first order of asymptotic components. From the equations, contribution of damping elements on modal damping is derived in consideration of multiple modes. The sound absorbing materials are arranged in three-dimensional rooms according to this contribution and the components of eigenvectors at the evaluation points. The availability of this method is verified using an expansion type chamber.
- Published
- 2008
38. Evolution of Novel Studies on Thermofluid Dynamics with Combustion
- Subjects
Active Combustion Control ,Pressure Oscillation ,Oscillatory Combustion ,Noise - Abstract
This paper mentions the recent development of combustion control technology and describes some results on theactive combustion control system for suppressing flame instabilities. As for the combustion control technology, there arethree typical elements including their coupling effects; thermoacoustic, heat release and fluid dynamics. In this research,development of the active combustion control system is carried out experimentally, which is based on a thermoacousticcontrol and a flame structure control. As the thermoacoustic approach, a feedback control system using a loudspeaker isdeveloped, and furthermore a flame structure control system is also investigated using a secondary injection method.Both results of the thermoacoustic and the flame structure control show a good performance of suppressing the pressureoscillation.
- Published
- 2008
39. 伝達情報量に基づくX線画像画質評価法に関するシミュレーション実験
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noise ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,image quality ,resolution ,transmitted information ,entropy - Abstract
Although radiographic image quality is considered difficult to evaluate in a straightforward and systematic manner. it may be possible by using an index of transmitted information. As a preliminary study, relations between transmitted information and two image characteristics, namely. image noise and image blurring, were evaluated by simulation. The value of transmitted information was decreased if image noise and image blurring increased. The relationships were corroborated on an experimental basis. This paper suggests the possibility of a simple, straightforward method for synthetically evaluating radiographic images by a single parameter in terms of transmitted information.
- Published
- 2007
40. 自己補償型ラングミュアプローブ測定系におけるノイズ低減の試み
- Subjects
Plasma ,Physics::Plasma Physics ,Circuit ,RF ,Probe ,Noise - Abstract
Although the method of inserting electrodes probes in a plasma is effective to determine electron temperature, electron density and plasma potential, many problems have been appeared in the real measurements of the physical properties of plasma for using ordinary electrical probes. One of these difficulties is the noise which is contained in the signals through the probe. This paper proposes a new method of the noise suppression. The isolation between circuits for measurements and power lines in high frequency regions, reduces the peak to peak value of noise currents significantly, namely below 10μA., プラズマ中に電極を挿入して測定を行う手法は,電子温度,電子密度そしてプラズマポテンシャルの値を決定するのに効果的であるが,一般的な静電プローブを用いたとしても,プラズマの物理的特性を実際に測定する際には多くの問題が持ち上がってくる。これらの問題の一つにプローブからの信号に含まれるノイズの存在がある。本論文は,このノイズを抑制する新規の手法を提案している。高周波領域において測定回路と電力線間を絶縁することで,ノイズ電流のピークピーク値を10μAと大幅に抑制した。
- Published
- 2007
41. A Noise Reduction Method in Calculating Correlation of FFT-GPS
- Subjects
IFFT ,GPS ,ドップラー効果 ,Navigation message ,平均化 ,相関計算 ,Doppler effect ,FFT ,Correlation ,Averaging ,雑音 ,Phase ,位相 ,Noise ,Narrow band ,航法メッセージ ,狭帯域化 - Abstract
金沢大学理工研究域 電子情報学系, 近年,全地球測位システム(GPS)は携帯電話に搭載され,また,子供や徘徊老人の位置確認等に威力を発揮するなど,その応用は大きく広がっている.いろいろな環境で使用されるため,受信電波が弱いことや環境雑音が大きいなどのために測位精度が低下するという問題がある.また,パーソナルな携帯性が求められるため小型化,低電力化が重要となる.本稿では,GPSの耐雑音特性の改善及び計算量の低減について検討する.GPSでは受信コードと参照コードの相関計算により,衛星とその衛星からの距離を求めている.ドップラー効果により搬送周波数が変動するが,これを補正するために膨大な計算が必要とされる.これを効率的に計算する方式としてFFTを用いる方式が提案されている.雑音の影響を低減する方法は平均化と狭帯域化の方法が用いられる.平均化の場合は平均を計算する時間区間長が問題となる.平均化の区間長を長くとれば雑音低減効果が高くなるが,航法メッセージにより位相反転が生じるため,平均化の区間長には制限がある.この問題を解決する方法を提案し,特に,受信レベルが低く,雑音の影響が大きい場合において従来法よりも有効であることを確認した. In recent years, Global Positioning System (GPS) has been widely used. The GPS system will be built into cellular phones of the third generation by April 2007. The number of GPS terminal units will be greatly increased. However, accuracy of positioning is not enough under severe environments, for instance very weak received signals, high level noises and so on. Furthermore, a huge of computations is required for calculating correlation between the received code and the reference codes stored in the GPS receiver. For calculating the correlation in the GPS system, FFT and IFFT have been effectively applied in order to save the amount of computations. However, a large number of computations is still required. Furthermore, the carrier frequency is slightly changed by the Doppler effect. This deviation is compensated for in the frequency domain. In some environments, where the received signal is weak compared to the noises, integration over multiple code periods to detect the peak of the correlation is required. On the other hand, there is a limitation for the integration interval due to a period of the navigation message. In this paper, a technique is proposed for removing the influence of the navigation messages. As a result, the amount of the frequency corrections is decreased, the computational complexity is also decreased by approximately 40 percent of the conventional method.
- Published
- 2006
42. Jumping behavior of heald in a shedding motion of loom
- Author
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Akamura, Taketo, Kinari, Toshiyasu, Shimokawa, Tomotsugu, Miyashita, Daisuke, Mochizuki, Yoshikazu, and Shintaku, Sukenori
- Subjects
Heald ,Warp tension ,Shedding motion ,Weaving machine ,Noise - Abstract
金沢大学理工研究域機械工学系, Noise in weaving mills has become very serious problem with increasing speed of weaving machine in recent years. One of these sources of noise is the collision sound of healds caused by shedding motion. It was clarified in our previous paper that the collision sound of healds is significantly connected with motion of heald during a period of shedding motion. In this research, therefore, photographs of the behavior of heald in a shedding period were taken by using a high-speed-camera system on a model shedding device. At the same time, noise was measured to investigate the collision sound of healds. Collision between healds and heald bar caused by heald jumping and the collision of healds were observed. It was confirmed that noise is the largest at the both collision timings. On the other hand, it has been already understood that the tension of warp yarn significantly affects the behavior of heald. It was also observed that the collision of heald and heald bar was delayed or eliminated with increasing tension of warp yarn by photographic observation. At the same time, noise was decreased with increasing warp tension. © 2006 The Textile Machinery Society of Japan.
- Published
- 2006
43. Aeroacoustic Simulation around a Circular Cylinder by the Equations Split for Incompressible Flow Field and Acoustic Field
- Author
-
KATO, Yoshihiro, MEN'SHOV, Igor, and NAKAMURA, Yoshiaki
- Subjects
Numerical Analysis ,Aerodynamic Acoustics ,Aeroacoustics ,Wave ,Computational Fluid Dynamics ,Noise - Abstract
A method for computational aeroacoustics using the equations split into the incompressible flow part and the acoustic part is investigated in this paper. The equations derived based on Mach number expansion, and the method to solve them with high accuracy and stability are shown. The finite volume method using WENO scheme is applied to the acoustic field around a circular cylinder. Comparing the present method with the approximate solution based on the acoustic analogy, it is found that the acoustic field has been decayed according to the square root of the distance from the object further from about 10 times the diameter. In addition, 15 grid points per a wave length can give a sufficiently accurate solution by the present method.
- Published
- 2005
44. 制振材を積層した自動車車体用パネルの減衰特性の有限要素解析 : 第1報, ビードパネルの減衰特性の実験結果と数値計算結果の比較
- Subjects
Condensed Matter::Soft Condensed Matter ,Automobile ,Noise ,Damping ,Damping Material ,Computer Aided Analysis ,Sound-Proof Structure - Abstract
This paper describes vibration phenomena for stiffened elastic panels having viscoelastic damping layer. The panels are stiffened by beads. The laminated panels are modeled using three-dimensional finite elements in consideration with complex modulus of elasticity. Further, applying asymototic method to the discreted equations of motion, explicit expressions of modal loss factors for the laminates are derived. Consequently, the expressions have similar form to Modal Strain Energy Method, which is proposed by Jonson. Numerical code is developed related to the expressions. Vibration damping properties of the bead panels, which are calculated by the code, is consistent with experimental results. Temperature dependence of the damping properties by FEM also agreed well with the experiments. These investigations reveal that modal damping decreases due to beads of the panels.
- Published
- 2003
45. Sound Radiation from Ventilation Aperture with Circular Thin Air Layer Setting up Machinery Wall : Noise Attenuation by Using Active Noise Sources
- Subjects
Active Noise Control ,genetic structures ,Machine Tool ,Filtered-XLMS ,Circular Slit Resonator ,sense organs ,Noise ,eye diseases ,Noise Control - Abstract
This paper describes insulation characteristics of slit resonator that a single channel ANC system for silencing leakage noise at ventilation aperture of package. The circular slit resonator composed of thin air layer that is radial expansion with very short axial length was set up package wall. The circular thin air layer is driven by one to four speakers that are controlled using Filtered-X-LMS algorithm to minimize sound power at error microphone. The experimental results show that the noise reduction region spreads to the high frequency side, as the slit depth decreases. The noise reduction quantity increases, as the slit width widens. Visualization of SPL and phase on the circular slit resonator indicate that the noise reduction mechanism is the interference of control sound and noise.
- Published
- 2002
46. Damping Analysis of 3D Acoustic Fields Involving Sound Absorbing Materials Using FEM
- Subjects
Automobile ,Modal Strain and Kinetic Energy Method ,Noise ,Damping ,Damping Material ,Computer Aided Analysis ,Sound Absorbing Material - Abstract
This paper deals with analysis for acoustic properties of three-dimensional closed sound fields having sound absorbing materials. In this analysis, the sound absorbers can have arbitrary shapes and can be located anywhere in the fields. The fields involve gas and sound absorbers which are modeled using Finite Element Method. A new three-dimensional element are developed for the absorbers. This element has two damping parameters which are complex density and complex volume elasticity. The elements are constructed, and then the corresponding simultaneously coupled equations are solved to obtain the frequency response. Further, a new expression is also derived to get distribution of contribution to modal damping for each element. These approachs are applied to three-dimensional rooms where the absorbers exist in different positions. The results are compared with the experiments carried out by Utsuno and are discussed.
- Published
- 2002
47. 駆動電流波形制御による直流モータの騒音抑制法
- Subjects
Quantitative Biology::Subcellular Processes ,High Frequency ,Motor ,Control ,Current ,Wave ,Noise ,DC-Motor ,Vibration - Abstract
Since a commutator of the DC-motor is divided into a number of segments to have the torque in the circumference direction, the currents in the coils of the rotor vary and have alternative waves during the rotor rotation even in a constant input voltage. The currents become sharp waves, so that they have high frequency component. This implies that the rotor shaft and the case of motor are excited electromagnetic forces with high frequency components. Since high frequency noises are loud when they are input to human ears, so that when high frequency vibrations are suppressed, noises become small. From the situation, this paper discusses a method of noise reduction of Dc Motor. In the method, the current waves are controlled to be sinusoidal waves. The method and the control algorithm are given. In order to validate the method, experimental tests are carried out. It is proven that our method is applicable to the motor noise control.
- Published
- 1999
48. Aerodynamic Sounds Generated by Curved Columns in a Uniform Air Flow
- Subjects
Aeolian Tone ,Sound ,Curved Column ,Frequency Analysis ,Aerodynamic Acoustics ,Uniform Air Flow ,Noise ,Broad Band Noise - Abstract
This paper deals with aerodynamic sounds generated by the curved columns in a uniform air flow experimentally. The curved column is formed in V-shape by bending a straight column to an angle of 2θ. The angle θ means the angle between the direction of air flow and a one-sided straight part of V-shaped column. The bend part has a radius of curvature of R. In the experiment, the effects of θ's and R's on the aerodynamic sound have been examined in detail. The results of the frequency analyses of aerodynamic sounds show that when θ≤90°, eminent aeolian tones are generated by the curved columns and moreover, that the peak frequencies of aeolian tones are affected by the values of R and θ. However, when θ > 90°aeolian tones are not generated but whistling noises generated in a broad frequency range.
- Published
- 1998
49. 一様気流中に弾性支持された円柱の振動及び放射音
- Subjects
Physics::Fluid Dynamics ,Computer Science::Sound ,Aerodynamic Sound ,Circular Cylinder ,Noise ,Flow-induced Vibration - Abstract
This paper deals experimentally with aerodynamic sound generated by an elastically supported circular cylinder in a uniform air-flow. The circular cylinder is supported by two. plate springs-at both ends. The air-flow induces vibrations on the circular cylinder and generates aerodynamic sounds. In the experiment, the frequency spectra of cylinder vibration and radiated sound are analyzed. As a result, it becomes clear that the sound generated from the elastically supported circular cylinder is larger than the sound from the fixed one, when the frequency of Karman vortex agrees with the natural frequency of the circular cylinder.
- Published
- 2004
50. Studies on Combustion and Exhaust emissions in a High Speed Diesel Engine : 2nd Report, Combustion, Vibration and Noise of Water-in-Oil Type Emulsified Fuel
- Subjects
Ignition Improver ,Emulsified Fuel ,Combustion ,Physics::Chemical Physics ,Diesel Engine ,Noise ,Vibration ,Physics::Atmospheric and Oceanic Physics - Abstract
This paper deals with quantitatively the influence of water emulsified fuel on combustion, engine vibration and noise, and the effect of ignition improver on the reduction of vibration and noise. The main conclusions obtained are as follows : (1) With an increase in the water addition rate, ignition delays and the maximum pressure rise rate increases. As a result, engine vibration and noise increase, in proportion to the pressure rise rate. (2) An increase in ignition delay with the addition of water is closely related to the heat quantity required to evaporate water in the fuel spray under a high temperature and high pressure condition. (3) Increases in engine vibration and noise due to the addition of water can be reduced by adding a small amount of ignition improver without aggravating engine performance., 日本機械学會論文集. B編, 54(498), pp.513-517; 1988
- Published
- 1988
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