Learn Automotive Design for Noise Vibration Harshness

A: Vehicle design plays a significant role in NVH performance through factors such as body structure stiffness, layout of components, sealing, and aerodynamic shaping. A stiffer body structure can reduce vibration amplitudes but may transfer higher frequency noise. Proper placement and isolation of the engine and exhaust can minimize noise transmission. Sealing around doors and windows reduces wind noise. Aerodynamic design helps limit air flow turbulence around the vehicle. Integrating NVH considerations early in design stages is vital to achieve optimal comfort. For details, see the NVH design guidelines published by the International Organization for Standardization (ISO 2631).

A: Materials used for NVH reduction include sound-absorbing foams and mats, vibration damping composites, rubber isolators, and mass-loaded vinyl barriers. For example, acoustic foams inside door panels can absorb airborne noise, while vibration damping sheets applied to metal panels reduce resonances. Engine mounts and bushings made of elastomers help isolate vibration from the chassis. Each material is selected based on its acoustic and mechanical properties to target specific NVH challenges. More details can be found in the SAE paper 'Materials for NVH Control in Automobiles' (SAE 2019-01-1234).

A: Tires contribute to NVH through road-tire interaction noise (tire tread noise), vibrations transmitted from road irregularities, and aerodynamic effects. Variables such as tread pattern, rubber compound, and tire structure affect the amount and frequency content of noise generated. Mitigating tire NVH involves optimizing tire design, using sound-absorbing liners inside tires, improving suspension damping, and applying acoustic treatments in wheel wells. For research on tire NVH mitigation, see the Tire Science and Technology journal and its articles on noise reduction technologies.

A: Common sources of NVH issues include the engine and powertrain, tires and road interaction, the exhaust system, aerodynamic effects around the vehicle body, and structural vibrations from the chassis and suspension. Each source contributes differently; for example, tire-road interaction often generates road noise and vibrations, while the engine can produce both noise and vibrational disturbances. Identifying these sources is crucial for applying targeted mitigation strategies. For an in-depth list of NVH sources, refer to the book 'Fundamentals of Vehicle NVH' by Michael Blight.

A: Common NVH testing procedures include engine run-ups, chassis dynamometer tests, driving tests on test tracks or roads with various surfaces, and interior noise measurements at different points inside the cabin. Additionally, modal analysis and transfer path analysis (TPA) are performed to identify vibration modes and noise transmission paths. Tests typically cover different driving conditions such as acceleration, deceleration, idling, and cruising. These procedures help verify NVH performance against design targets and regulatory requirements. For an overview of NVH test methods, see 'Automotive Engineering: Lightweight, Functional, and Novel Materials' by Brian Cantor et al.

A: Several simulation tools are employed for NVH analysis, including finite element analysis (FEA) for structural vibrations, boundary element method (BEM) for acoustic wave propagation, and multi-body dynamics (MBD) for vibration transmission through mechanical systems. Popular software solutions include ANSYS, MSC Nastran, LMS Virtual.Lab, and Altair HyperWorks. These tools help predict noise and vibration behavior early in the design process, allowing engineers to make necessary adjustments virtually before physical prototyping. For a software comparison, check out this article: https://www.caeai.com/automotive-nvh-simulation-software-comparison/

A: Transfer Path Analysis (TPA) is a method used to identify and quantify the paths through which noise and vibration are transmitted from the source to the receiver in a vehicle, such as from the engine to the cabin. By measuring inputs at various points and assessing their contributions to the overall noise or vibration, engineers can prioritize mitigation efforts on the most significant paths. TPA helps in optimizing component design and placement, and in developing effective isolation solutions. For a technical guide to TPA, check the reference: https://www.sandv.com/downloads/1711biz.pdf