Active Control of Fan Noise by Vane Actuators

An active noise control system for ducted fan noise was built that uses actuators located in stator vanes. The actuators were piezoelectric benders manufactured using the THUNDER technology and were custom designed for the application. The active noise control system was installed in the NASA ANCF rig. Four actuator array with a total of 168 actuators in 28 stator vanes were used. Simultaneous reductions of acoustic power in both the inlet and exhaust duct were demonstrated for a fan disturbance that contained two radial mode orders in both inlet and exhaust. Total power levels in the target modes were reduced by up to 9 dB in the inlet and total tone levels by over 6 dB while exhaust power levels were reduced by up to 3 dB. Far field sound pressure level reductions of up to 17 dB were observed. A simpler control system, matched to the location of the disturbance with two radial actuator arrays, was demonstrated to control total acoustic power in four disturbance modes simultaneously in inlet and exhaust. The vane actuator met the requirements given for the ANCF, although in practice the performance of the system was limited by the constraints of the power amplifiers and the presence of control spillover. The vane actuators were robust. None of the 168 vane actuators failed during the tests

ACTIVE NOISE CONTROL USING CARBON NANOTUBE THERMOPHONES: CASE STUDY FOR AN AUTOMOTIVE HVAC APPLICATION

The goal of this project was to reduce the overall noise levels emitted by the HVAC components in a vehicle’s cabin. More specifically, the feasibility of achieving this goal using two key technologies was investigated. The first of these technologies, Active Noise Control (ANC), is a noise attenuation technique that relies on destructive interference that “cancels” unwanted noise. Typically used in situations where physical constraints prevent passive attenuation techniques from being used, ANC is known for its high size-to-effectiveness ratio. This benefit cannot be gained without a cost however; the complexity of ANC systems is significantly higher than their passive counterparts. This is due to the signal processing and actuator designs required. These actuators often take the form of moving-coil loudspeakers which, while effective, are often bulky. Because of this they are difficult to “drop in” to an existing system. This is where the second technology comes in. Carbon Nanotube (CNT) Thermophones are solid-state speakers that operate by using rapid heat fluctuations to create sound. Called the “thermoacoustic effect,” (TE) the theory of this operating principle dates to the turn of the 20th century. Useful demonstration of TE did not occur until 2008, however, when researchers first developed the first CNT thermophones. The hallmark characteristics of these transducers are their small size and flexible nature. Compared to traditional loudspeakers they have a much smaller form factor and are more versatile in terms of where they can be placed in a cramped system. The marriage of CNT transducers to ANC technology shows promise in improving the application space and ease of installation of ANC systems. Getting these two to cooperate, however, is not without challenges. A case study for this union is presented here; the application space being the ducted environment of vehicle HVAC systems

Implementation of manifold bridge tuning for noise control of an automotive intake system.

The considerable effort invested by automobile manufacturers to attenuate various noise sources within the passenger compartment has resulted in other sources such as induction noise having become more noticeable. This study was undertaken to investigate the feasability of using a non conventional noise cancellation technique to improve the acoustic performance of the induction system by introducing exhaust noise into the intake system through a manifold bridge. The effectiveness of this technique was first investigated using Ricardo Wave, a computational, engine simulation, software program. Using a one-dimensional, finite-difference approach to analyse the dynamics of the pressure waves, mass flows, and energy losses within the ducts, an optimized bridge configuration was determined. A physical model incorporating the design of the optimized bridge was installed and tested on a motored engine for comparison to the numerical results. The realized attenuation of induction noise due to the manifold bridge was evaluated using 1/12th octave frequency spectra and three-dimensional colour maps of both the unmodified and bridged engine for steady state and transient engine cases. A sound quality analysis was also performed using various psychoacoustic metrics including loudness, sharpness, roughness and fluctuation strength. Both the numerical and experimental models demonstrated reductions in the overall sound level measured at the intake opening with the experimental results being more favourable. While the results of the sound quality analysis correlated well between the numerical and experimental models, the success of the bridging technique was somewhat ambiguous, depending on the sound quality metric used. As with the traditional analysis techniques, the reported loudness was lower for the numerical and experimental bridged engines. Sharpness was found not to be a relevant metric in this study due to a lack of high frequency content to the noise. Depending on the engine speed, values for roughness and fluctuation strength were either improved or diminished with the implementation of the manifold bridge. For the conditions tested, implementation of the manifold bridge has demonstrated promise. Before it can be declared commercially viable, however, further considerations such as the effects of exhaust gas recirculation and fired engine tests, are warranted.Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .N68. Source: Dissertation Abstracts International, Volume: 66-11, Section: B, page: 6097. Thesis (Ph.D.)--University of Windsor (Canada), 2005

Design considerations for a monolithic, GaAs, dual-mode, QPSK/QASK, high-throughput rate transceiver

A monolithic, GaAs, dual mode, quadrature amplitude shift keying and quadrature phase shift keying transceiver with one and two billion bits per second data rate is being considered to achieve a low power, small and ultra high speed communication system for satellite as well as terrestrial purposes. Recent GaAs integrated circuit achievements are surveyed and their constituent device types are evaluated. Design considerations, on an elemental level, of the entire modem are further included for monolithic realization with practical fabrication techniques. Numerous device types, with practical monolithic compatability, are used in the design of functional blocks with sufficient performances for realization of the transceiver

LASER Tech Briefs, September 1993

This edition of LASER Tech briefs contains a feature on photonics. The other topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, Life Sciences and books and reports

Feasibility study of common electronic equipment for shuttle sortie experiment payloads

A study was conducted to determine the feasibility of using standardized electronic equipment on the space shuttle vehicle in an effort to reduce the cost estimates. The standards for Nuclear Instrument Modules (NIM) and CAMAC electronic equipment are presented and described. It was determined that the CAMAC electronic equipment was more suitable for use with the space shuttle systems. Specific applications of the CAMAC equipment are analyzed. Illustrations of the equipment and circuit diagrams of the subsystems are provided

Technology 2002: The Third National Technology Transfer Conference and Exposition, volume 2

Proceedings from symposia of the Technology 2002 Conference and Exposition, December 1-3, 1992, Baltimore, MD. Volume 2 features 60 papers presented during 30 concurrent sessions

NASA Tech Briefs, June 1992

Topics covered include: New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

A Multi-Band Far-Infrared Survey with a Balloon-Borne Telescope

Nine additional radiation sources, above a 3-sigma confidence level of 1300 Jy, were identified at 100 microns by far infrared photometry of the galactic plane using a 0.4 meter aperture, liquid helium cooled, multichannel far infrared balloon-borne telescope. The instrument is described, including its electronics, pointing and suspension systems, and ground support equipment. Testing procedures and flight staging are discussed along with the reduction and analysis of the data acquired. The history of infrared astronomy is reviewed. General infrared techniques and the concerns of balloon astronomers are explored