Browse Topic: Noise, Vibration, and Harshness (NVH)
ABSTRACT A methodology based on a combination of commercial software tools is developed for rendering complex acoustic scenes in real time. The methodology aims to bridge the gap between real time acoustic rendering algorithms which lack important physics for the exterior urban environment and more rigorous but computationally expensive geometric or wave-based acoustics software by incorporating pre-computed results into a real time framework. The methodology is developed by surveying the best in class commercial software, outlining a general means for accommodating results from each, and identifying areas where supplemental capability is required. This approach yields a real time solution with improved accuracy. Strengths and limitations in current commercial technologies are identified and summarized
ABSTRACT Awareness of the surroundings is strongly influenced by acoustic cues. This is of relevance for the implementation of safety strategies on board of electric and hybrid vehicles and for the development of acoustic camouflage of military vehicles. These two areas of research have clearly opposite goals, in that developers of electric vehicles aim at adding the minimum amount of exterior noise that will make the EV acoustically noticeable by a blind or distracted pedestrian, while the developers of military vehicles desire to implement hardware configurations with minimum likelihood of acoustic detectability. The common theme is the understanding of what makes a vehicle noticeable based the noise it generates and the environment in which it is immersed. Traditional approaches based on differences of overall level and/or one-third octave based spectra are too simplistic to represent complex scenarios such as urban scenes with multiple sources in the soundscape and significant
ABSTRACT Under the sponsorship of TARDEC, UTRC is developing 5–10 kW Solid Oxide Fuel Cell (SOFC) Auxiliary Power Units (APU) that will be capable of operating on JP-8 with a sulfur concentration of up to the specification’s upper limit of 3000 ppmw. These APUs will be sized to fit within the relatively tight space available on U.S. Army vehicles such as the Abrams, Bradley and Stryker. The objective of the base development program that commenced in August 2010 is a 1000 hour TRL-5 demonstration of an APU in an Abrams configuration by mid-2013. This SOFC system is expected to provide power to the 28 VDC vehicle bus at a net efficiency ≥35%. In addition, the noise level is anticipated to be far below that generated by combustion engine-based APU concepts. UTRC has completed the Preliminary Design of the system and has finalized the overall system configuration and the requirements for each of the components. During the Preliminary Design phase, evaluations of the performance of sub
ABSTRACT When we assess compliance of crew exposure to vibration within a military tracked vehicle we use international standards, these are ISO 2631 and BS 6841. Within these standards, weighting factors based on research carried out 40 years ago are applied to the measured vibration. These weighing filters attenuate and remove vibration above 80Hz. After conducting tests for over 30 years, it is the author’s intention to prove that these filters are no longer fit for purpose and the standards need revisiting
ABSTRACT Curtiss-Wright has developed an acoustic based sensor technology for measuring friction, shock, and dynamic load transfer between moving parts in machinery. This technology provides a means of detecting and analyzing machine structure borne ultrasonic frequency sounds caused by friction and shock events between the moving parts of the machine. Electrical signals from the sensors are amplified and filtered to remove unwanted low frequency vibration energy. The resulting data is analyzed as a computed stress wave energy value that considers the amplitude, shape, duration and rates of all friction and shock events that occur during a reference time interval. The ability to separate stress waves from the lower frequency operational noise makes this technology capable of detecting damaged gears/bearings and changes in lubrication in equipment earlier than other techniques, and before failure progression increases cost of repair. Already TRL9 in adjacent industries, this technology
WHY DO WE NEED SIMULATIONS? This paper is intended to provide a broad presentation of the simulation techniques focusing on transmission testing touching a bit on power train testing. Often, we do not have the engine or vehicle to run live proving ground tests on the transmission. By simulating the vehicle and engine, we reduce the overall development time of a new transmission design. For HEV transmissions, the battery may not be available. However, the customer may want to run durability tests on the HEV motor and/or the electronic control module for the HEV motor. What-if scenarios that were created using software simulators can be verified on the test stand using the real transmission. NVH applications may prefer to use an electric motor for engine simulation to reduce the engine noise level in the test cell so transmission noise is more easily discernable
Over the past twenty years, the automotive sector has increasingly prioritized lightweight and eco-friendly products. Specifically, in the realm of tyres, achieving reduced weight and lower rolling resistance is crucial for improving fuel efficiency. However, these goals introduce significant challenges in managing Noise, Vibration, and Harshness (NVH), particularly regarding mid-frequency noise inside the vehicle. This study focuses on analyzing the interior noise of a passenger car within the 250 to 500 Hz frequency range. It examines how tyre tread stiffness and carcass stiffness affect this noise through structural borne noise test on a rough road drum and modal analysis, employing both experimental and computational approaches. Findings reveal that mid-frequency interior noise is significantly affected by factors such as the tension in the cap ply, the stiffness of the belt, and the properties of the tyre sidewall
This Aerospace Information Report (AIR) is limited in scope to the general consideration of environmental control system noise and its effect on occupant comfort. Additional information on the control of environmental control system noise may be found in 2.3 and in the documents referenced throughout the text. This document does not contain sufficient direction and detail to accomplish effective and complete acoustic designs
Bemis Manufacturing and BASF collaborated to develop a lighter-weight and lower-cost hydraulic tank for compact excavators that was recognized with a lightweighting award traditionally reserved for automotive innovations. Receiving an honorable mention in the Enabling Technology category of this year's Altair Enlighten Awards, the development team leveraged a combination of injection molding and vibration welding techniques to lower costs by approximately 20% and reduce mass by about 5% compared to the traditional roto-molding process. The solution also is more eco-efficient, delivering both environmental savings (reductions in lifecycle CO2 emissions) and reducing lifecycle costs
Vehicle HVAC noise performance is an important vehicle design validation criterion since it significantly links the brand image of a vehicle. It affects the customer’s buying decision and the business of selling vehicles because it directly affects driving comfort. Customers expect continuous improvement in HVAC noise without compromising cooling performance. The process of cascading vehicle-level acoustic performance to subsystem and component levels becomes an important factor in the vehicle NVH development process. It was found that the component-level [HVAC unit without duct] performance of an HVAC system measured in an anechoic chamber was at par when compared to targets, whereas the subsystem-level performance [HVAC unit with duct and dashboard] was on the higher side of the targets. Advanced NVH tools were used to identify the source of noise at the subsystem level. It helped to locate the source and its transfer path. A design modification done at the transfer path location
Moisture adsorption and compression deformation behaviors of Semimet and Non-Asbestos Organic brake pads were studied and compared for the pads cured at 120, 180 and 240 0C. The 2 types of pads were very similar in moisture adsorption behavior despite significant differences in composition. After being subjected to humidity and repeated compression to 160 bars, they all deform via the poroviscoelastoplastic mechanism, become harder to compress, and do not fully recover the original thickness after the pressure is released for 24 hours. In the case of the Semimet pads, the highest deformation occurs with the 240 °C-cure pads. In the case of the NAO pads, the highest deformation occurs with the 120 0C-cure pads. In addition, the effect of pad cure temperatures and moisture adsorption on low-speed friction was investigated. As pad properties change all the time in storage and in service because of continuously changing humidity, brake temperature and pressure, one must question any
The influence of moisture adsorption, prior braking, and deceleration rate on the low-speed braking noise has been investigated, using copper-free disc pads on a passenger car. With increasing moisture adsorption time, decreasing severity of prior braking or increasing deceleration rate, the noise sound level increases for the air-borne exterior noise as well as for the structure-borne interior noise. The near-end stop noise and the zero-speed start-to-move noise show a good correlation. Also, a good correlation is found between the noise measured on a noise dynamometer and on a vehicle for the air-borne noise. All the variables need to be precisely controlled to achieve repeatable and reliable results for dynamometer and vehicle braking groan noise tests. It appears that the zero-speed start-to-move vehicle interior noise is caused by the pre-slip vibration of the brake: further research is needed
Researchers have developed SPINDLE, a pioneering robotic rehabilitation system. Combining virtual reality (VR) with customized resistance training, SPINDLE offers personalized therapy to enhance strength and dexterity for activities of daily living (ADLs). Its adaptability and potential for home use represent a major advancement in tremor rehabilitation, with broader healthcare implications
Researchers at Chalmers University of Technology have developed an optical amplifier that they expect will revolutionize both space and fiber communication. The new amplifier offers high performance, is compact enough to integrate into a chip just millimeters in size, and crucially, does not generate excess noise
Radio frequency (RF) and microwave signals are integral carriers of information for technology that enriches our everyday life – cellular communication, automotive radar sensors, and GPS navigation, among others. At the heart of each system is a single-frequency RF or microwave source, the stability and spectral purity of which is critical. While these sources are designed to generate a signal at a precise frequency, in practice the exact frequency is blurred by phase noise, arising from component imperfections and environmental sensitivity, that compromises ultimate system-level performance
Researchers worldwide are currently working on the next evolution of communication networks, called “beyond 5G” or 6G networks. To enable the near-instantaneous communication needed for applications like augmented reality or the remote control of surgical robots, ultra-high data speeds will be needed on wireless channels. In a study published recently in IEICE Electronics Express, researchers from Osaka University and IMRA AMERICA have found a way to increase these data speeds by reducing the noise in the system through lasers
This procedure is applicable to modes from 500 Hz and 13000 Hz. The parameters measured with this procedure are defined as the damping factor, ξ, for the first nine vibration modes of the beam. The measurement will be done in free-free conditions and with temperature
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