Download or read book Noise Reduction Efforts for Special Operations C 130 Aircraft Using Active Synchrophaser Control written by and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aircraft noise often inhibits mission effectiveness. As a result, flight crews, ground maintenance personnel, and passengers suffer degraded voice communication, impaired performance, increased fatigue, and hearing loss. In an effort to reduce the level of noise both inside and outside of the aircraft, techniques have been developed that attempt to quiet the environment. The simplest approach uses passive noise reduction methods, including installing acoustic insulation and exhaust modifications, but these only provide limited success. A more complicated approach uses an active noise cancellation (ANC) system, which offers improved performance that can augment passive methods to significantly reduce both internal and external aircraft noise. ANC achieves noise reduction by creating an anti-noise, which is an equal and opposite acoustic wave that cancels the unwanted noise. This type of cancellation works well in smaller volumes, like headset ear cups. For larger volumes or environments, arrays of loudspeakers are needed, but are often ineffective due to their size and weight. Since the primary noise on multi-engine turboprop aircraft, such as the C-130, originates from the engine-propeller system, the noise from one engine-propeller can be tuned to provide a canceling acoustic wave to reduce the noise generated from another engine-propeller on the same aircraft. Because the levels of noise generated from each engine-propeller combination are similar under normal operating conditions, a means to adjust the propeller phasing to create a noise canceling effect is needed. For multi-engine propeller-driven aircraft, engine-propeller phase control is accomplished using an electromechanical device called a synchrophaser. To optimally control the phase angle relationships among the four engine propellers, a controllable or active synchrophaser system is needed. The synchrophaser system described in this paper is a joint effort between AFRL and AFSOC.
Download or read book Aerodynamic Noise written by Tarit Bose and published by Springer Science & Business Media. This book was released on 2012-11-09 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamic Noise extensively covers the theoretical basis and mathematical modeling of sound, especially the undesirable sounds produced by aircraft. This noise could come from an aircraft’s engine—propellers, fans, combustion chamber, jets—or the vehicle itself—external surfaces—or from sonic booms. The majority of the sound produced is due to the motion of air and its interaction with solid boundaries, and this is the main discussion of the book. With problem sets at the end of each chapter, Aerodynamic Noise is ideal for graduate students of mechanical and aerospace engineering. It may also be useful for designers of cars, trains, and wind turbines.
Download or read book Potential Subjective Effectiveness of Active Interior Noise Control in Propeller Airplanes written by Clemans A. Powell and published by . This book was released on 2000 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active noise control technology offers the potential for weight-efficient interior noise reduction, particularly for propeller aircraft. However, there is little information on how passengers respond to this type of interior noise control. This paper presents results of two experiments that use sound quality engineering practices to determine the subjective effectiveness of hypothetical active noise control (ANC) systems in a range of propeller aircraft. The two experiments differed by the type of judgments made by the subjects: pair comparisons based on preference in the first and numerical category scaling of noisiness in the second. Although the results of the two experiments were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference. The reductions in subjective response due to the ANC conditions were predicted with reasonable accuracy by reductions in measured loudness level. Inclusion of corrections for the sound quality characteristics of tonality and fluctuation strength in multiple regression models improved the prediction of the ANC effects.
Download or read book Potential Subjective Effectiveness of Active Interior Noise Control in Propeller Airplanes written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-16 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active noise control technology offers the potential for weight-efficient aircraft interior noise reduction, particularly for propeller aircraft. However, there is little information on how passengers respond to this type of interior noise control. This paper presents results of two experiments that use sound quality engineering practices to determine the subjective effectiveness of hypothetical active noise control (ANC) systems in a range of propeller aircraft. The two experiments differed by the type of judgments made by the subjects: pair comparisons based on preference in the first and numerical category scaling of noisiness in the second. Although the results of the two experiments were in general agreement that the hypothetical active control measures improved the interior noise environments, the pair comparison method appears to be more sensitive to subtle changes in the characteristics of the sounds which are related to passenger preference. The reductions in subjective response due to the ANC conditions were predicted with reasonable accuracy by reductions in measured loudness level. Inclusion of corrections for the sound quality characteristics of tonality and fluctuation strength in multiple regression models improved the prediction of the ANC effects.Powell, Clemans A. and Sullivan, Brenda M.Langley Research CenterEFFECTIVENESS; ACTIVE CONTROL; SENSITIVITY; PROPELLER NOISE; NOISE REDUCTION; AIRCRAFT NOISE; PROPELLERS; PROCEDURES; PASSENGERS; LOUDNESS; JUDGMENTS; CORRECTION; AIRCRAFT COMPARTMENTS; SOUND TRANSDUCERS
Download or read book Special Operations Forces written by United States. General Accounting Office and published by . This book was released on 1998 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Active Control Techniques for Noise Reduction in an Aircraft Fuselage Model written by James D. Jones and published by . This book was released on 1987 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optimal Guidance and Control for Investigating Aircraft Noise impact Reduction written by Elwood C. Stewart and published by . This book was released on 1978 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Airframe Noise Reduction Challenge written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: The NASA goal of reducing external aircraft noise by 10 dB in the near-term presents the acoustics community with an enormous challenge. This report identifies technologies with the greatest potential to reduce airframe noise. Acoustic and aerodynamic effects will be discussed, along with the likelihood of industry accepting and implementing the different technologies. We investigate the lower bound, defined as noise generated by an aircraft modified with a virtual retrofit capable of eliminating all noise associated with the high lift system and landing gear. However, the airframe noise of an aircraft in this 'clean' configuration would only be about 8 dB quieter on approach than current civil transports. To achieve the NASA goal of 10 dB noise reduction will require that additional noise sources be addressed. Research shows that energy in the turbulent boundary layer of a wing is scattered as it crosses trailing edge. Noise generated by scattering is the dominant noise mechanism on an aircraft flying in the clean configuration. Eliminating scattering would require changes to much of the aircraft, and practical reduction devices have yet to receive serious attention. Evidence suggests that to meet NASA goals in civil aviation noise reduction, we need to employ emerging technologies and improve landing procedures; modified landing patterns and zoning restrictions could help alleviate aircraft noise in communities close to airports.Lockard, David P. and Lilley, Geoffrey M.Langley Research CenterAEROACOUSTICS; AIRFRAMES; AIRCRAFT NOISE; NOISE REDUCTION; AIRCRAFT CONFIGURATIONS; WINGS; FLAPS (CONTROL SURFACES); VORTICES; TRAILING EDGES
Download or read book Noise Reduction and Communications in the CC 130 Hercules Aircraft written by and published by . This book was released on 2001 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this project was to study ways of creating a better acoustical environment for the crew of the search and rescue CC 130 Hercules aircraft. The ultimate goals were to improve communications & reduce noise, thus preserving hearing. Several commercial products were tested to assess their effectiveness in accomplishing the two goals. The products included various active noise reduction headsets, the communication ear plug (CEP), and the standard issue communications headset. The microphone in real ear technique was used in human subjects to assess the amount of attenuation provided by each headset when exposed to 97 decibels of mauve noise. A binaural acoustic test mannequin was used to assess the amount of attenuation offered by the CEP in the same environment. Human subjects were also subjected to the modified Rhyme test in combination with the maximum likelihood procedure to determine the signal to noise ratio required for each communications device to achieve a level of 60% speech intelligibility. Based on the results, the device that provided the greatest amounts of noise attenuation is identified.
Download or read book An Assessment of Propeller Aircraft Noise Reduction Technology written by and published by . This book was released on 1995 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Project Report written by United States. Office of Noise Abatement and Control and published by . This book was released on 1976 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Estimate of Aircraft Flyover Noise Reduction by Application of Active Noise Control to Engine Fan Tones written by R. E. Kraft and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Special Issue written by and published by . This book was released on 2008 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Noise Control in Aircraft written by Sven Johansson and published by . This book was released on 1998 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Veggie tales God wants me to give them written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Special Operations Forces C 130 Upgrade Plan Could Help Fix Electronic Warfare Deficiencies written by and published by . This book was released on 1998 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: In response to a concern that threats to the U.S. Special Operations Command's (USSOCOM) aircraft are increasing, while funds available for electronic warfare are decreasing, the General Accounting Office (GAO) are reviewing USSOCOM'S acquisition strategy for aircraft electronic warfare systems. This report focuses on fixed-wing C-130 aircraft operated by USSOCOM'S Air Force component, the Air Force Special Operations Command (AFSOC). As requested, GAO determined (1) the soundness of AFSOC's electronic warfare acquisition strategy and (2) the extent to which AFSOC is correcting deficiencies and maximizing commonality in its electronic warfare systems. GAO also identified a funding source that could help AFSOC further implement its electronic warfare acquisition strategy. GAO will address USSOCOM'S rotary-wing aircraft in a separate report. The nation's special operations forces provide the National Command Authorities a highly trained, rapidly deployable joint force capable of conducting special operations anywhere in the world. In November 1986 Congress enacted section 1311 of Public Law 99-661, which directed the President to establish USSOCOM, a unified combatant command to ensure that special operations forces were combat ready and prepared to conduct specified missions. USSOCOM'S component commands include AFSOC, the Army Special Operations Command, the Naval Special Warfare Command and the Joint Special Operations Command. AFSOC, located at Huriburt Field, Florida, deploys and supports special operations forces worldwide. To ensure that special operations were adequately funded, Congress further provided in section 1311 of Public Law 99-661 that the Department of Defense create for the special operations forces a major force program (MFP) category for the Future Years Defense Plan of the Department of Defense.
Download or read book Guide to Industrial Control Systems ICS Security written by Keith Stouffer and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
