A complex of analytical models for predicting noise in an aircraft cabin

A series of analytical calculated models for predicting the noise in an aircraft cabin is developed: an orthotropic model, a model with discrete frames, a model with discrete stringers, a model with isolated cells, and a model with a cross system of discrete ribs. The analytical solution is constructed on the basis of the method of space harmonic expansion. Vibrations are represented in the form of double trigonometric series. Strict periodicity allows dividing the series into a large number of independent groups, which makes it possible to effectively perform calculations for large fragments of the fuselage in the entire frequency region both for deterministic and random external force fields.     

The vibro-acoustic response and analysis of a full-scale aircraft fuselage section for interior noise reduction

The surface and interior response of a Cessna Citation fuselage section under three different forcing functions (10-1000 Hz) is evaluated through spatially dense scanning measurements. Spatial Fourier analysis reveals that a point force applied to the stiffener grid provides a rich wavenumber response over a broad frequency range. The surface motion data show global structural modes (approximately < 150 Hz), superposition of global and local intrapanel responses (approximately 150-450 Hz), and intrapanel motion alone (approximately > 450 Hz). Some evidence of Bloch wave motion is observed, revealing classical stop/pass bands associated with stiffener periodicity. The interior response (approximately < 150 Hz) is dominated by global structural modes that force the interior cavity. Local intrapanel responses (approximately > 150 Hz) of the fuselage provide a broadband volume velocity source that strongly excites a high density of interior modes. Mode coupling between the structural response and the interior modes appears to be negligible due to a lack of frequency proximity and mismatches in the spatial distribution. A high degree-of-freedom finite element model of the fuselage section was developed as a predictive tool. The calculated response is in good agreement with the experimental result, yielding a general model development methodology for accurate prediction of structures with moderate to high complexity.     

Propeller aircraft interior noise model,part I: Analytical model

Theoretical results are given for a basic propeller aircraft interior noise model. Results allow prediction of tonal levels in the cabin of a propeller-driven airplane at the blade passage frequency and its harmonics. Part I of this paper contains the analytical model, and in Part II scale-model and flight test comparisons are considered.     

Propeller aircraft interior noise model,part II: Scale-model and flight-test comparisons

Part I [1] of this paper contains the theory used to create a basic propeller aircraft interior noise model. The model predicts tonal levels of blade passage harmonics in the cabin of a propeller driven aircraft. Part II presents the results of validation studies based on scale-model and flight comparisons.     

Development and experimental validation of analytical thermal models for the evaluation of the depth of laser-treated zones

Received: 5 January 1998/Accepted: 27 March 1998     

Sound quality prediction of vehicle interior noise using deep belief networks

The sound quality of vehicle interior noise strongly influences passengers’ psychological and physiological perceptions. To predict the sound quality of interior noise, a vehicle road test with four compact cars has been conducted. All recorded interior noise signals have been denoised via a discrete wavelet transform (DWT) denoising procedure and subsequently evaluated subjectively through the anchor semantic differential (ASD) test by a jury. In addition, a novel prediction method, namely, regression-based deep belief networks (DBNs), which substitute the support vector regression (SVR) layer for the linear softmax classification layer at the top of the general DBN’s structure, has been proposed to predict the interior sound quality. The parameter selection of the DBN model has been compared and studied using a grid search. In addition, four conventional machine-learning-based methods have been introduced to enable a comparison of the performance with the newly developed DBNs. Furthermore, the feature fusion ability of DBNs has been studied by varying the amount of information that the dataset offers. The results show the following: (1) The accuracy and robustness of the proposed DBN-based sound quality prediction approach are better than those of the 4 other referenced methods. (2) The multiple-feature fusing process can strongly affect the prediction performance. (3) Finally, the unsupervised pre-training process of the DBNs can enhance the information fusing ability. Finally, the newly proposed regression-based DBN approach may be extended to address other vehicle noises in the future.     

The design of synthesized structural acoustic sensors for active control of interior noise with experimental validation

In this paper, the feasibility of using synthesized structural acoustic sensors (SSAS) for active noise control inside irregularly shaped enclosures is investigated. A SSAS consists of a cluster of inter-connected discrete PVDF elements, located on the surface of a vibrating structure enclosing a sound field. An optimal design ensures the sensor output to be directly related to the acoustical potential energy inside the enclosure. Hence, synthesized structural acoustic sensors can provide error signals for an active noise control system, and the use of microphones inside the enclosure can be avoided. A cylindrical shell with a floor partition, which can be used to model an aircraft cabin, is used as a test case. PZT actuators are used as control actuators. Both SISO (single input and single output) and MIMO (multi-input and multi-output) control systems are optimally designed using Genetic Algorithms and implemented with a Filtered-X Feedforward LMS (least-mean-square) controller. Their control performances are evaluated with different types of disturbances. To show the effectiveness of the optimal design approach, some non-optimal control systems are also tested and compared with the optimal one. It is shown that with optimally designed SSAS, an active structural acoustic control system can effectively reduce noise inside the enclosures without using any acoustic transducers.     

Honking noise corrections for traffic noise prediction models in heterogeneous traffic conditions like India

In developing countries like India, the nature of the composition of traffic is heterogeneous. A heterogeneous traffic flow consists of vehicles that have different sizes, speeds, vehicle spacing and operating characteristics. As a result of the widely varying speeds, vehicular dimensions, lack of lane disciplines, honking becomes inevitable. In addition, it changes the urban soundscape of developing countries. In heterogeneous traffic conditions, horn events increase noise level (L_den) by 0.5–13 dB(A) as compared to homogenous traffic conditions. Therefore, the traffic prediction models that are used for homogenous traffic conditions are not applicable in heterogeneous traffic conditions. To increase the accuracy of noise prediction models, in depth understanding of heterogeneous traffic noise is required. Understanding the real traffic noise characteristics requires quantification of some of the basic traffic flow characteristics such as speed, flow, Level Of Service (LOS) and density. In a given roadway, the noise level changes with density and LOS on the road. In this paper, a new factor for horn correction is introduced with respect of Level Of Service (LOS). The horn correction values can be incorporated in traffic noise models such as CRTN, FHWA, and RLS 90, while evaluating heterogeneous traffic conditions.     

Development and validation of consensus machine learning-based models for the prediction of novel small molecules as potential anti-tubercular agents

Molecular Diversity - Tuberculosis (TB) is an infectious disease and the leading cause of death globally. The rapidly emerging cases of drug resistance among pathogenic mycobacteria have been a...     

The effect of motion on acoustic dipole models for aerodynamic noise prediction

The effect of motion on acoustic dipole models for aerodynamic noise is shown to greatly alter their directivity patterns. When this effect is included in an analysis of airframe noise measurements, directivity patterns computed with acoustic surface dipoles are in better agreement with observations than those obtained with edge dipole sources.     

An assessment of certain causal models used in surveys on aircraft noise annoyance

The causal relationships which have so far been proposed between aircraft noise exposure, annoyance and certain “psycho-social” variables (fear of aircraft crashing, general attitude towards aviation, etc.), are re-analysed, and it is demonstrated that by using correlational analysis one can arrive at contradictory results. From the sociological surveys undertaken to date, one can derive only an ordered sequence of verbal reactions to aircraft noise, and not a causal sequence between these verbal reactions: the only clear cause of annoyance is the noise itself.It is suggested that future surveys on noise annoyance should include personality tests and health questionnaires, if one wishes to establish reliable causal sequences.     

金属烧结丝网在内场消声中的应用

利用试验手段研究暂冲式风洞稳定段内安装不同规格烧结金属丝网对风洞上游控制阀后气流噪声和湍流度抑制作用。试验结果表明:多层金属烧结丝网可在全频段内大幅度降低上游气流的噪声,最大可达21 dB;消声量与金属烧结丝网无量纲的压力损失系数成正比,压力降与金属烧结丝网层数呈现出非线性叠加的结果。另外发现烧结金属烧结丝网对气流速度脉动亦具有突出的抑制效果。例如,试验段马赫数Ma=1.5时,120目26层+160目26层组合烧结金属丝网出口气流速压脉动幅值减小为入口来流的18%,湍流度由11.7%降至3%。因此金属烧结丝网适合于暂冲式风洞的内场降噪。     

A measurement model for general noise reaction in response to aircraft noise

In this paper a measurement model for general noise reaction (GNR) in response to aircraft noise is developed to assess the performance of aircraft noise annoyance and a direct measure of general reaction as indicators of this concept. For this purpose GNR is conceptualized as a superordinate latent construct underlying particular manifestations. This conceptualization is empirically tested through estimation of a second-order factor model. Data from a community survey at Frankfurt Airport are used for this purpose (N=2206). The data fit the hypothesized factor structure well and support the conceptualization of GNR as a superordinate construct. It is concluded that noise annoyance and a direct measure of general reaction to noise capture a large part of the negative feelings and emotions in response to aircraft noise but are unable to capture all relevant variance. The paper concludes with recommendations for the valid measurement of community reaction and several directions for further research.     

考虑噪声烦恼度的机场飞机噪声收费模型和应用研究

随着我国民航运输业的飞速发展,机场噪声影响问题日趋严重。通过向航空公司或旅客收取噪声费来进行治理,是民航发达国家的普遍做法,也是我国未来的发展方向。该文在国外机场飞机噪声收费模型的基础上,提出了基于飞机噪声特性、噪声烦恼度、噪声治理投入费用和资金回收周期等因素的机场噪声收费模型。模型将机场噪声治理费用通过合理的回收周期按一定比例分配到各年度,再根据飞机噪声特性、噪声烦恼度将每年噪声收费分配到每架次飞机(或每位旅客)。飞机噪声特性根据ACI的机场噪声分级R1～R8来确定,噪声烦恼度借助Mamdani模型构建。应用表明,该收费模型关键因素考虑全面,计算方法先进简洁,费率合理。对于噪声较高飞机,夜间起飞收费为1219.06元/架次,客均收费10.16元;对于噪声很低的飞机,昼间着陆收费为66.10元/架次,客均收费仅0.15元。费率确定符合国际民航组织倡导的以支定收原则,有助于形成航空公司/旅客减噪激励机制同时又不致抑制机场航空业务增长。