Active Control Of Aircraft Cabin Noise
Active Control Of Aircraft Cabin Noise

Author: Ignazio Dimino

Publisher: World Scientific

Published: 2015-07-13

Total Pages: 303

ISBN-13: 1783266597

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'The text is well written and supported by clear and useful illustrations. This would be a useful textbook for postgraduate or advanced undergraduate studies and would also make a good introductory text for engineers moving into the field. The literature survey and bibliography provide a useful starting point for further study.'The Aeronautical JournalActive Control of Aircraft Cabin Noise provides a bridge to fill the gap between robust control theory and practical applications of active noise control systems in aircraft cabin. Both the possibilities and limitations of structural solutions to enhance aircraft cabin comfort by reducing interior noise are discussed supported by a wide range of topics in engineering, from finite element modeling to multichannel adaptive feed-forward control, usually dealt separately in the literature. In addition, experimental noise attenuation results with passengers' subjective perceptions predicting the effects of cabin noise on comfort assessments is examined. Theoretical and experimental research is detailed enough to capture the interest of the non-expert in engineering who wishes to have an overview of some of the active noise control applications in aircraft. This book may be used as an advanced textbook by graduate and undergraduate students in aeronautical engineering, and would be an authoritative resource book for research into the subject.

Large Civil Tiltrotor (Lctr2) Interior Noise Predictions Due to Turbulent Boundary Layer Excitation
Large Civil Tiltrotor (Lctr2) Interior Noise Predictions Due to Turbulent Boundary Layer Excitation

Author: National Aeronautics and Space Adm Nasa

Publisher: Independently Published

Published: 2019-01-14

Total Pages: 44

ISBN-13: 9781794075979

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The Large Civil Tiltrotor (LCTR2) is a conceptual vehicle that has a design goal to transport 90 passengers over a distance of 1800 km at a speed of 556 km/hr. In this study noise predictions were made in the notional LCTR2 cabin due to Cockburn/Robertson and Efimtsov turbulent boundary layer (TBL) excitation models. A narrowband hybrid Finite Element (FE) analysis was performed for the low frequencies (6-141 Hz) and a Statistical Energy Analysis (SEA) was conducted for the high frequency one-third octave bands (125- 8000 Hz). It is shown that the interior sound pressure level distribution in the low frequencies is governed by interactions between individual structural and acoustic modes. The spatially averaged predicted interior sound pressure levels for the low frequency hybrid FE and the high frequency SEA analyses, due to the Efimtsov turbulent boundary layer excitation, were within 1 dB in the common 125 Hz one-third octave band. The averaged interior noise levels for the LCTR2 cabin were predicted lower than the levels in a comparable Bombardier Q400 aircraft cabin during cruise flight due to the higher cruise altitude and lower Mach number of the LCTR2. LCTR2 cabin noise due to TBL excitation during cruise flight was found not unacceptable for crew or passengers when predictions were compared to an acoustic survey on a Q400 aircraft. NASA/CR-2013-218005, NF1676L-16365 Grosveld, Ferdinand W. Langley Research Center

Coupled Structural-acoustic Analytical Models for the Prediction of Turbulent Boundary-layer-induced Noise in Aircraft Cabins
Coupled Structural-acoustic Analytical Models for the Prediction of Turbulent Boundary-layer-induced Noise in Aircraft Cabins

Author: Joana Luíz Torres da Rocha

Publisher:

Published: 2010

Total Pages:

ISBN-13:

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Significant interior noise and vibrations in aircraft cabins are generated by the turbulent flow over the fuselage. The turbulent boundary layer (TBL) excitation is the most important noise source for jet powered aircraft during cruise flight. Reduced levels of interior noise are desirable both for comfort and health reasons. However, to efficiently design noise control systems, and to design new and optimized structures that are more efficient in the noise reduction, a clearer understanding of the sound radiation and transmission mechanisms is crucial. This task is far from being straightforward, mainly due to the complexity of the system consisted by the aircraft fuselage, and all the sound transmission mechanisms involved in a such complex environment. The present work aims to give a contribution for the understanding of these mechanisms.

Analysis of Acoustic Modeling and Sound Propagation in Aircraft Noise Prediction
Analysis of Acoustic Modeling and Sound Propagation in Aircraft Noise Prediction

Author: National Aeronautics and Space Adm Nasa

Publisher: Independently Published

Published: 2018-09-23

Total Pages: 76

ISBN-13: 9781723942693

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An analysis has been performed of measured and predicted aircraft noise levels around Denver International Airport. A detailed examination was made of 90 straight-out departures that yielded good measurements on multiple monitors. Predictions were made with INM 5, INM 6 and the simulation model NMSIM. Predictions were consistently lower than measurements, less so for the simulation model than for the integrated models. Lateral directivity ("installation effect") patterns were seen which are consistent with other recent measurements. Atmospheric absorption was determined to be a significant factor in the underprediction. Calculations of atmospheric attenuation were made over a full year of upper air data at seven locations across the United States. It was found that temperature/humidity effects could cause variations of up to +/-4 dB, depending on season, for the sites examined. It was concluded that local temperature and humidity should be accounted for in aircraft noise modeling.Plotkin, Kenneth J. and Shepherd, Kevin P. (Technical Monitor)Langley Research CenterNOISE PREDICTION; AIRCRAFT NOISE; ACOUSTIC PROPAGATION; SOUND PROPAGATION; NOISE INTENSITY; MODELS; TEMPERATURE EFFECTS; DIRECTIVITY