Browse Topic: Noise, Vibration, and Harshness (NVH)
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
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
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
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
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
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
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
Airplane manufacturers running noise tests on new aircraft now have a much cheaper option than traditional wired microphone arrays. And it’s sensitive enough to help farmers with pest problems. The wireless microphone array that one company recently created with help from NASA can locate crop-threatening insects by listening for sound they make in fields. And now, it’s making fast, affordable testing possible almost anywhere
The transition from ICE to electric power trains in new vehicles along with the application of advanced active and passive noise reduction solutions has intensified the perception of noise sources not directly linked to the propulsion system. This includes road noise as amplified by the tire cavity resonance. This resonance mainly depends on tire geometry, gas temperature inside the tire and vehicle speed and is increasingly audible for larger wheels and heavier vehicles, as they are typical for current electrical SUV designs. Active technologies can be applied to significantly reduce narrow band tire cavity noise with low costs and minimal weight increase. Like ANC systems for ICE powertrains, they make use of the audio system in the vehicle. In this paper, a novel low-cost system for road induced tire cavity noise control (RTNC) is presented that reduces the tire cavity resonance noise inside a car cabin. The approach is cheap in terms of computational effort (likewise ICE order
When dealing with the structural behavior of a car body, analyzing the dynamic distortion in all body closure openings in a complete vehicle, provides a better understanding of the body characteristics compared to traditional static load cases such as static torsional body stiffness. This is particularly relevant for non-traditional vehicle layouts and electric vehicle architectures where mass distribution and in particular battery mass and stiffness play a completely different effect with respect to the internal combustion engine vehicles. A methodology typically adopted to measure the body response, e.g. when driving a vehicle on a rough pavé road, is the so-called Multi Stethoscope (MSS). The MSS is measuring the distortion in each body closure opening in two diagonals. During the virtual development, the distortion is described by the relative displacement in diagonal direction in time domain using a modal transient analysis. The results are shown as Opening Distortion Fingerprint
When traveling in an open-jet wind tunnel, the path of an acoustic wave is affected by the flow causing a shift of source positions in acoustical maps of phased arrays outside the flow. The well-known approach of Amiet attempts to correct for this effect by computing travel times between microphones and map points based on the assumption that the boundary layer of the flow, the so-called shear layer, is infinitely thin and refracts the acoustical ray in a conceptually analogy to optics. However, in reality, the turbulent nature of both the not-so-thin shear layer and the acoustic emission process itself causes an additional smearing of sources in acoustic maps, which in turn causes deconvolution methods based on these maps – the most prominent example being CLEAN-SC – to produce certain ring effects, so-called halos, around sources. In this paper, we intend to cast some light on this effect by describing our path of analyzing/circumventing these halos and how they are linked to the
Tire/Road noise is a dominant contribution to a vehicle interior noise and requires significant engineering resources during vehicle development. A process has been developed to support automotive OEMs with road noise engineering during vehicle design and development which has test as its basis but takes advantage of simulation to virtually accelerate road noise improvement. The process uses noise sources measured on a single tire installed on a test stand in a chassis dynamometer. The measured sources are then combined with vehicle level transfer functions calculated using a Finite-Element model for structure-borne noise and a Statistical Energy Analysis (SEA) model for airborne noise to predict the total sound at the driver’s ears. The process can be applied from the initial stages of a vehicle development program and allows the evaluation of vehicle road noise performance as perceived by the driver long before the first prototype is available. This process is also extensible to
Encapsulations of E-drive systems are gaining importance in electric mobility, since they are a simple measure to improve the noise behavior of the drive. Current experimental evaluation methods, however, pose substantial challenges for the test personnel and are associated with considerable effort in both time and cost. Evaluating the encapsulation on an e-drive test bed, for example, requires a functional e-drive and test bed resources. Evaluations in the vehicle on the other hand make objective assessments difficult and are subject to increasingly limited availability of prototype vehicles fit for NVH testing. To overcome these challenges, AVL has developed a new experimental evaluation method for the NVH efficiency of e-drive encapsulations. In this method, the e-drive is freely suspended in a semi-anechoic chamber and its structure is excited using shakers while the radiated noise with and without encapsulation is measured. The NVH efficiency of the encapsulation is evaluated by
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