Development and validation of preliminary analytical models for aircraft interior noise prediction

1982 ◽  
Vol 82 (4) ◽  
pp. 541-575 ◽  
Author(s):  
L.D. Pope ◽  
D.C. Rennison ◽  
C.M. Willis ◽  
W.H. Mayes
2014 ◽  
Vol 118 (1208) ◽  
pp. 1125-1135 ◽  
Author(s):  
M. J. Kingan

Abstract The purpose of this paper is to describe the current status of open rotor noise prediction methods and to highlight future challenges in this area. A number of analytic and numerical methods are described which can be used for predicting ‘isolated’ and ‘installed’ open rotor tonal noise. Broadband noise prediction methods are also described and it is noted that further development and validation of the current models is required. The paper concludes with a discussion of the analytical methods which are used to assess the acoustic data collected during the high-speed wind-tunnel testing of a model scale advanced open rotor rig.


Author(s):  
E Latorre Iglesias ◽  
J Xia ◽  
ME Farooq ◽  
A Bistagnino ◽  
J Sapena

Noise emissions play a key role in the development of environment-friendly rolling stock. Noise limits given by EU directives for interoperability purposes but also by internal directives of the different countries where any kind of rolling stock operates have to be respected for train approval. Exterior noise predictions are used nowadays to validate the design of new rolling stock. These predictions are used within the companies to evaluate the different design options, to optimize costs, to assess the risks and for virtual certification in cases where existing products are modified. Potentially predictions could be used in the future for a complete virtual certification of the train allowing to decrease or even to completely avoid the noise tests that are currently carried out by the train manufacturers. As a consequence, the cost of the certification process will be reduced. One of the challenges for a complete virtual certification is the assessment of uncertainties in the predictions as probably this will not be accepted by the stakeholders without a defined and validated uncertainty assessment. This work presents a methodology to estimate the uncertainty of the predictions of train noise emissions. An example of the application of the proposed framework for uncertainty evaluation is provided for a typical suburban rolling stock showing the feasibility of its use for railway exterior noise predictions but potentially also for interior noise calculations and for different applications other than railway.


Author(s):  
Joana da Rocha ◽  
Afzal Suleman ◽  
Fernando Lau

Flow-induced noise in aircraft cabins can be predicted through analytical models or numerical methods. However, the analytical methods existent nowadays were obtained for simple structures and cabins, in which, usually, a single panel is excited by the turbulent flow, and coupled with an acoustic enclosure. This paper discusses the development of analytical models for the prediction of aircraft cabin noise induced by the external turbulent boundary layer (TBL). The coupled structural-acoustic analytical model is developed using the contribution of both structural and acoustic natural modes. While, in previous works, only the contribution of an individual panel to the cabin interior noise was considered, here, the simultaneous contribution of multiple flow-excited panels is also analyzed. The analytical models were developed for rectangular and cylindrical cabins. The mathematical models were successfully validated through the good agreement with several independent experimental studies. Analytical predictions are presented for the interior sound pressure level (SPL) at different locations inside the cabins. It is shown that identical panels located at different positions have dissimilar contributions to the cabin interior noise, showing that the position of the vibrating panel is an important variable for the accurate prediction of cabin interior noise. Additionally, the results show that the number of vibrating panels significantly affects the interior noise levels. It is shown that the average SPL, over the cabin volume, increases with the number of vibrating panels. The space-averaged SPL is usually accepted to provide the necessary information for the noise prediction. However, in some real life applications, the local sound pressure may be desirable. To overcome this point, the model is also able to predict local SPL values, at specific locations in the cabin, which are also affected by number of vibrating panels, and often differ from the average SPL values. The developed analytical model can be used to study a wide range of different systems involving a cabin coupled with vibrating panels, excited by the TBL. The properties of the external flow, acoustic cabin, and panels, as well as the number of vibrating panels, can be easily changed to represent different systems. These abilities of the model make it a solid basis for future investigations involving the implementation of noise reduction techniques and multidisciplinary design optimization analyzes.


2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Joana da Rocha ◽  
Afzal Suleman ◽  
Fernando Lau

The turbulent boundary layer is a major source of interior noise in transport vehicles, mainly in aircraft during cruise flight. Furthermore, as new and quieter jet engines are being developed, the turbulent flow-induced noise will become an even more important topic for investigation. However, in order to design and develop systems to reduce the cabin interior noise, the understanding of the physical system dynamics is fundamental. In this context, the main objective of the current research is to develop closed-form analytical models for the prediction of turbulent boundary-layer-induced noise in the interior of aircraft cylindrical cabins. The mathematical model represents the structural-acoustic coupled system, consisted by the aircraft cabin section coupled with the fuselage structure. The aircraft cabin section is modeled as a cylindrical acoustic enclosure, filled with air. The fuselage structure, excited by external random excitation or by turbulent flow, is represented through two different models: (1) as a whole circular cylindrical shell with simply supported end caps and (2) as a set of individual simply supported open circular cylindrical shells. This paper presents the results obtained from the developed analytical framework and its validation through the successful comparison with several experimental studies. Analytical predictions are obtained for the shell structural vibration and sound pressure levels, for the frequency range up to 10,000 Hz.


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