Search Results

The innovation and application of new technologies in battery electric vehicle (BEV) development continues to be a key objective of the automotive industry. One such area of development is glazing designs that reduce transmission of noise into vehicle interiors. Highly asymmetric laminated front side lites that consist of thick soda lime glass exterior plies laminated with thinner ion exchanged interior plies with acoustic polyvinyl butyral interlayers offer substantially reduced noise transmission compared to industry standard monolithic front side lites. These asymmetric laminate designs also provide additional benefits of improved toughness and penetration resistance. This paper documents a study that uses a systematic test-based approach to understand the sensitivity of interior vehicle noise behavior to changes in acoustic attenuation driven by installation of asymmetric laminated glass front side lites.

It is a common practice to conduct NVH fingerprinting and benchmarking assessments at the powertrain level, to understand source level noise and vibration. To assess the NVH influence of engine, e-motor, and transmission, sub-system testing is often conducted in addition to full powertrain testing. These powertrain or sub-system investigations provide valuable information regarding the status of “source” level excitations relative to targets and / or competitive powertrains. In the case of transmissions and e-machines, it is particularly important to understand source level tonal content and how this will be perceived at the vehicle level. However, variation in component design results in differences in order content, which complicates the process of objectively comparing multiple products. Multiple methods are presented here for characterizing tonal content of transmission and e-machines, based on assessments conducted in a component hemi-anechoic dynamometer test cell.

The automotive industry continues to develop new powertrain and vehicle technologies aimed at reducing overall vehicle-level fuel consumption. Specifically, the use of electrified propulsion systems is expected to play an increasingly important role in helping OEM’s meet fleet CO2 reduction targets for 2025 and beyond. Electric and hybrid electric vehicles do not typically utilize IC engines for low-speed operation. Under these low-speed operating conditions, the vehicles are much quieter than conventional IC engine-powered vehicles, making their approach difficult to detect by pedestrians. To mitigate this safety concern, many manufacturers have synthesized noise (using exterior speakers) to increase detection distance. Further, the US National Highway Traffic Safety Administration (NHTSA) has provided recommendations pursuant to the Pedestrian Safety Enhancement Act (PSEA) of 2010 for such exterior noise signatures to ensure detectability.

The automotive industry continues to develop technologies for reducing vehicle fuel consumption. Specifically, vehicle lightweighting is expected to be a key enabler for achieving fleet CO2 reduction targets for 2025 and beyond. Hybrid glass laminates that incorporate fusion draw and ion exchange innovations are thinner and thereby, offer more than 30% weight reduction compared to conventional automotive laminates. These lightweight hybrid laminates provide additional benefits, including improved toughness and superior optics. However, glazing weight reduction leads to an increase in transmission of sound through the laminates for certain frequencies. This paper documents a study that uses a systematic test-based approach to understand the sensitivity of interior vehicle noise behavior to changes in acoustic attenuation driven by installation of lightweight glass.

Automotive companies are studying to add extra value in their vehicles by enhancing powertrain sound quality. The objective is to create a brand sound that is unique and preferred by their customers since quietness is not always the most desired characteristic, especially for high-performance products. This paper describes the process of developing a brand powertrain sound for a high-performance vehicle using the DFSS methodology. Initially the customer's preferred sound was identified and analyzed. This was achieved by subjective evaluations through voice-of-customer clinics using vehicles of similar specifications. Objective data were acquired during several driving conditions. In order for the design process to be effective, it is very important to understand the relationship between subjective results and physical quantities of sound. Several sound quality metrics were calculated during the data analysis process.

The definition of vehicle and powertrain level NVH targets is one of the first tasks toward establishing where a vehicle's NVH behavior will reside with respect to the current or future state of industry. Realization of vehicle level NVH targets relies on a combination of competitive powertrain (source) and vehicle (path) NVH performance. Assessment of vehicle NVH sensitivity is well understood, and can be accomplished through determination of customer interface NVH response to measured excitations at the source input locations. However, development of appropriate powertrain source targets can be more difficult, particularly related to sound quality. This paper discusses various approaches for definition of powertrain targets for sound quality, with a specific focus on impulsive noise.

Increased customer expectation for NVH refinement creates a significant challenge for the integration of Diesel powertrains into passenger vehicles that might have been initially developed for gasoline engine applications. A significant factor in the refinement of Diesel powertrain sound quality is calibration optimization for NVH, which is often constrained by performance, emissions and fuel economy requirements. Vehicle level enablers add cost and weight to the vehicle and are generally bounded by vehicle architecture, particularly when dealing with a carry-over vehicle platform, as is often the case for many vehicle programs. These constraints are compounded by the need to make program critical sound package content decisions well before the availability of prototype vehicles with the right powertrain. In this paper, a case study on NVH development for integration of a light duty Diesel powertrain is presented.

The electrification of vehicle propulsion has changed the landscape of vehicle NVH. Pure electric vehicles (EV) are almost always quieter than those powered by internal combustion engines. However, one of the key challenges with the development of range extended electric vehicles (ReEV) is the NVH behavior of the vehicle. Specifically, the transition from the EV mode to one where the range extender engine is operational can cause significant NVH issues. In addition, the operation of the range extender engine relative to various driving conditions can also pose significant NVH concerns. In this paper internal combustion engines are examined in terms of their acoustic behavior when used as range extenders. This is done by simulating the vibrations at the engine mounting positions as well as the intake and exhaust orifice noise. By using a transfer path synthesis, interior noise components of the range extenders are calculated from these excitations.

The definition of vehicle and powertrain level targets is one of the first tasks toward establishing where a vehicle will reside with respect to the current or future state of industry. Though development of sound quality metrics is ongoing to better correlate objective data with subjective assessments, target setting at the vehicle level is relatively straightforward. However, realization of these targets depends on effective cascading to system and component levels. Often, component level targets are derived based on experience from earlier development programs, or based on selected characteristics observed during component level benchmarking. An approach is presented here to complement current strategies for component level target definition. This approach involves a systematic concept for definition of component NVH targets based on desired vehicle level performance and a consequent target break down.

It is important to develop powertrain NVH characteristics with the goal of ultimately influencing/improving the in-vehicle NVH behavior since this is what matters to the end customer. One development tool called dB(VINS) based on a process called Vehicle Interior Noise Simulation (VINS) is used for determining interior vehicle noise based on powertrain level measurements (mount vibration and radiated noise) in combination with standardized vehicle transfer functions. Although this method is not intended to replace a complete transfer path analysis and does not take any vehicle specific sensitivity into account, it allows for powertrain-induced interior vehicle noise assessments without having an actual test vehicle available. Such a technique allows for vehicle centric powertrain NVH development right from an early vehicle development stage.

It is commonly accepted that refined “powertrain sound quality” is essential to the development of a vehicle which will be well received by today's discriminating automotive customer. However, though there are several metrics which correlate well with a subjective impression of powertrain level inputs, what is ultimately important is the sound quality at driver's ear. Vehicle level powertrain sound quality is influenced by the powertrain noise and vibration (source) as well as the vehicle airborne and structureborne transfer functions (path). In development as well as benchmarking activities, it can be difficult to separate the influence of source and path on overall vehicle sound quality.

The electrification of vehicle propulsion has caused a significant change in many areas including the world of vehicle acoustics. Comments from the media currently range from “silently hums the future” to “electric car roars with V8 sound”. Decades of experience in designing brand-specific vehicle sound based on noise and vibration generated by combustion engines cannot be simply transferred to the upcoming vehicles driven purely by electric powertrains. Although electric vehicles are almost always considerably quieter than those powered by internal combustion engines, the interior noise is characterized by high-frequency noise components which can be subjectively perceived as annoying and unpleasant. Moreover, such disturbing noise is no longer masked by combustion engine noise. Fundamental questions regarding the sound design of electric vehicles have yet to be answered: it remains unclear what exactly the interior noise of an electric vehicle should sound like.

NVH refinement is an important aspect of the powertrain development and vehicle integration process. The depletion of fossil-based fuels and increase in price of gasoline have prompted most vehicle manufacturers to embrace propulsion technologies with varying degrees and types of hybridization. Many different hybrid vehicle systems are either on the market, or under development, even up to all-electric vehicles. Each hybrid vehicle configuration brings unique NVH challenges that result from a variety of sources. This paper begins with an introductory discussion of hybrid propulsion technologies and associated unique vehicle NVH challenges inherent in the operation of such hybrid vehicles. Following this, the paper outlines a two-dimensional landscape of typical customer vehicle maneuvers mapped against hybrid electric vehicle (HEV) operational modes.

NVH refinement is an important aspect of the powertrain development process. Powertrain NVH refinement is influenced by overall sound levels as well as sound quality. The sound quality and hence the level of powertrain NVH refinement can be negatively affected by the presence of excessive impulsive noise. This paper describes a process used to develop an understanding of impulsive powertrain noise. The paper begins with an introductory discussion of various sources of impulsive noise in an automotive powertrain. Following this, the paper outlines a process for identifying the source of the impulsive powertrain noise using examples from case studies. The remainder of the paper focuses on certain examples of impulsive noise such as Diesel knocking noise, injector ticking, impulsive cranktrain noise, and gear rattle. For these examples, the development of key objective metrics, optimization measures, and improvement potential are examined.

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions. Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined.

Optimization of the interface between the powerplant and vehicle frame/body is critical to obtaining superior interior structureborne noise and vibration characteristics in the vehicle. This paper demonstrates the combination of new and existing simulation/experimental methodologies for powerplant integration, including results from case studies. Multi-body simulation based methodologies are used to optimize the location, number, and type of powerplant mounts on a vehicle, taking into account the input forcing from the engine and frequency-dependent mount properties. Upon obtaining the first prototype vehicle, a procedure to evaluate the effectiveness of the powerplant mounts using a vibrational power flow technique, is described. The influence of mount bracket resonances on interior vehicle sound is shown and a new procedure to optimize mount brackets, provided.

The sound quality and performance of an automotive engine are both significantly influenced by the “air-to-air” system, i.e., the intake system, the exhaust system, and the engine gas dynamics. Only a full systems approach can result in an optimized air-to-air system, which fulfills engine performance requirements, overall sound pressure level targets for airborne vehicle noise, as well as sound quality demands. This paper describes an approach, which considers the intake system, engine, and exhaust system within one CAE model that can be utilized for engine performance calculations as well as acoustic simulations. Examples comparing simulated and measured sound are discussed. Finally, the simulated sound (e.g., at the tailpipe of the exhaust system) is combined with an interior noise simulation technique to evaluate its influence inside the vehicle's interior.