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Vehicle incab booming perception, a low frequency response of the structure to the various excitations presents a challenging task for the NVH engineers. The excitation to the structure causing boom can either be power train induced, depending upon the number of cylinders or the road inputs, while transfer paths for the excitation is mainly through the power train mounts or the suspension attachments to the body. The body responds to those input excitations by virtue of the dynamic behavior mainly governed by its modal characteristics. This paper explains in detail an integrated approach, of both experimental and numerical techniques devised to investigate the mechanism for boom noise generation. It is therefore important, to understand the modal behavior of the structure. The modal characteristics from the structural modal test enable to locate the natural frequencies and mode shapes of the body, which are likely to get excited due to the operating excitations.

In worldwide automotive markets, the migration of customers towards smaller cars having compact, fuel-efficient design is well established and accepted as an engineering challenge by global automotive OEMs. Tata Motors of India has established a precedent by developing an ultra low cost and light weight car (the Nano), and has thereby created a new market segment for such cars that are more affordable to most of the population. This is now becoming established as a brand of low cost, safe transport in both rural and urban market segments. Despite the market moving towards such compact, fuel-efficient designs, customers are unwilling to lose many of the vehicle attributes to which they have been accustomed in previous types of entry-level cars. Addressing this marketing requirement places some significant challenges before the designers of this type of car.

For an automotive exhaust system, noise level and back pressure are the most important parameters for passenger comfort and engine performance respectively. The sound quality perception of the existing silencer design was unacceptable, although the back pressure measured was below the target limit. To improve the existing design, few concepts were prepared by changing the internal elements of silencer only. The design constraints were the silencer shell dimensions, volume of silencer, inlet pipe and outlet tailpipe positions, which had to be kept same as that of the existing base design. The sound quality signal replaying and synthesizing was performed to define the desired sound quality. The numerical simulation involves 3D computational fluid dynamics (CFD) with appropriate boundary condition having less numerical diffusions to predict the back pressure. The various silencer concepts developed with this preliminary analysis, was then experimentally verified with the numerical data.

Baffle plates with heat reactive expandable foam sealants have increasingly found their applications in automotives. They are used to separate body cavities and to impede noise, water and dust propagation inside of body cavities, thus control noise intrusion into the passenger compartment. Use of these sealant materials has grown significantly as the demands to improve vehicle acoustic performance has increased. Traditionally quantification of the acoustic performance of expandable baffle samples involved making separate vehicles with and without expandable baffles and measure the incab noise to know the effect. The absolute acoustic evaluation of the baffles is very difficult as number of other vehicle parameters is also responsible for vehicle incab noise. Also, it is a time consuming and a costly method to evaluate.

The idle NVH refinement gives the customer a feel of overall quality of the vehicle. The psycho-acoustic perception of the driver/passenger during idling is primarily influenced by the power train refinement and its isolation from the passenger compartment. Power train mounting system plays a vital role in attaining the required idle NVH refinement. The modern cars being designed for higher power to weight ratio, with more powerful engines and lighter frame work has made the task of NVH refinement more difficult. The response of the lighter structure to load variation at idle due to operation of ancillary systems like HVAC, and electrical systems such as head lamps, fog lamps, wipers etc. causes discomfort to the passenger. This paper describes an approach towards identifying the key factors governing the idle vibration of the vehicle in steady state as well as in transient operation.

Quality of the sound is one of the major parameter for the occupants comfort. The vehicle noise can be broadly classified into airborne and structure borne noise contributed by numerous aggregates present in vehicle. Among different vehicle aggregates the alternator, which is an important component in vehicle electrical architecture, can be considered as a major source of airborne noise. Generally, the alternator noise is combination of mechanical, aerodynamic, and electromagnetic sources. The ratio of these sources in the overall noise varies with speed and loading pattern. The mechanical and aerodynamic noise normally depends on speed while the electromagnetic noise variation is load dependent. Alternator whining is an irritant perception of the sound quality due to electromagnetic noise. When the alternator is loaded with electrical loads (like head lamp, tail lamp, wiper and HVAC) the sound level increases further.

The automotive trend is now days switching towards less weight, cost effective and power efficient powertrain. Consumer’s expectations from comfort and NVH point of view is rising day by day. The NVH performance of a powertrain is mainly affected by the powertrain mounting System. In design and development of a new vehicle, the mounting of the powertrain (engine-transmission assembly) receives special attention. The powertrain body is the major concentrated mass in the vehicle Which if not adequately confined and quarantined, it will result in poor NVH characteristics of powertrain. In this work a powertrain mounting System of three-cylinder engine, which is transversely mounted, is analyzed. A correlation between two different simulation techniques has been established. Passive mounts are being assessed throughout the investigation. A multi body simulation approach is employed for the modelling and simulation of powertrain mounting system.

The prime target of IEA (international energy association) to reduce global average emission by 50% in 2030 has prompted focused R&D on automotive emission reduction as well as NEV (new energy vehicles). Of these strategies, engine downsizing constitutes the group of strategies employed to meet lower emission and fuel consumption targets in IC engines. Downsizing strategies have been proved successful in reducing emissions. There is widespread trend of downsizing existing engines with a goal to produce lower emissions along with equal or better performance. To achieve the stated goals downsized engines are usually charged or employ higher compression ratios. This raises NVH as well as structural issues that need further analysis. While the concept of downsizing has been studied in deep, its structural effects and NVH related issues are of concern. This paper throws light into different engine downsizing strategies and their effect on NVH.

Legislations on vehicular noise levels are becoming stringent day by day. Also the customer expectations on the vehicle noise levels has also become more refined in the India market. Intake and exhaust flow noise levels are one of the major contributors to this overall noise level of the vehicle. These drivers have led the Indian automobile manufacturers to focus on engine and vehicle noise optimization. The 3-wheeler and 4-wheeler Quadra-cycle vehicles which are powered by single cylinder engines are more prone to high noise levels due to pulsating intake and exhaust flow dynamics caused by single firing cylinder. The study focuses on the exhaust muffler design optimization of a single cylinder engine powertrain to meet the targeted noise levels. One - Dimensional (1D) Simulation tools give significant information at the system level and reduce the time required for analysis and optimization compared to the three - dimensional (3D) CFD tools.

Indian cities are among the most polluted in the world. The transportation sector is one of the major sources of gaseous pollutants. In recent years, also the effects of climate change and global warming have been felt across the globe. India has therefore committed at the CoP26 summit in 2021 to reduce its CO2 emissions by 45% till the year 2030. The Indian automotive sector is already addressing the problem with implementation of the Stage 2 BS VI norms, CAFÉ & Stage V standards and pursuing rapid electrification with application of zero emission vehicles. India also has the largest rail network of Asia, and a significant proportion of greenhouse gases is emitted by this sector. Deployment of zero emission fuel cell trains would be one of the solutions to meet India’s emission reduction targets.

Reducing vehicular noise has become a crucial step in product development to meet stringent legislation and improve passenger experience. Smaller vehicles like three-wheelers and compact cars are often powered by a single cylinder engine due to product cost, packaging and weight constraints. Unlike a multi-cylinder engine where cylinders fire one after another which helps to reduce noise levels by destructive interference of pressure waves, a single cylinder engine produces higher noise levels due to firing of a single cylinder. Intake and exhaust flow noise is one of the dominant sources of vehicular noise. This study focuses on using CAE tools to reduce intake and exhaust flow noise levels to meet target noise requirements. One dimensional (1-D) gas dynamics simulation provides a good trade-off between accuracy and run-time, allowing for evaluation of multiple design iterations with acceptable accuracy in a relatively short time frame.