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Focus on Noise, Vibration, Harshness

Focus on Noise, Vibration, Harshness

By Juban Thomas:

NVH becomes the most important customer touch point as it can cause psychological and physiological fatigue and visual discomforts

Juban Thomas,VP – Global Testing & Vehicle Dynamics, R&D, CEAT

Generally, when the discussion regarding tyre performance comes to Indian Roads, rough roads with potholes comes to the mind. However, there are other performance focussed Indian roads with high speed capabilities making the Indian road infrastructure ‘Diverse.’ With better cars and better roads, the performance envelope of tyres becomes vital. In the past tyre development for OE and aftermarket, the ride and handling attributes were important. Today, considering the environmental impacts, rolling resistance becomes the top priority followed by comfort requirements. In the future, considering the electrification and autonomous vehicles, noise performance along with rolling resistance and comfort requirements becomes the top priorities. Besides these, the regulations and proposed tyre labelling from Government of India also adds another perspective in the new product development. Overall, NVH (Noise, Vibration, Harshness) becomes the most important customer touch point as it can cause psychological/physiological, fatigue and visual discomforts.

In tyre development programs to overcome the challenges mentioned, there are various approaches to develop from tyre pattern, cavity design, construction, compounds or materials. During such development programmes, there are multiple development tests which checks the performance metrics of a tyre both from a performance and durability point of view.
The first stage of development is checking the potential patterns based on the Rolling Resistance performance and evaluate In-Cabin noise, Ride and handling and braking characteristics. Based on the results, the best pattern is taken into development and the first proto tyres are tested extensively in the second stage of development. However, after such tests, there are occasional contradictions when the same tyres gets fitted to different vehicle make and body styles.
NVH objective data can also be a part of this contradiction. This challenge calls for test methodologies beyond the traditional approach like in-cabin noise data. Such approach requires quantifying the noise levels from occupant’s ear to tyre source levels which helps in identifying the probable causes to root cause. This is when diagnostic tools like tyre contact patch noise measurements, tyre cavity noise measurements comes in handy to understand the tyre noise source mechanisms.
Once, the details are understood, tyre can get into the cycle of optimization of pitch sequence, tread design and structure optimization. Simultaneously the tactile vibrations are studied and quantified on smooth roads at constant speeds and varying speeds along with rough road comfort performance. There is a good possibility that the replacement tyres can be fitted in alloy wheels or steel wheels. This option also changes the NVH performance quantification as the tyre/wheel transmissibility also changes. So it is important to understand this contribution to the vehicle NVH as well.
At CEAT Limited, we use these NVH test methodologies at a very early stage of product development to quantify the tyre NVH characteristics, diagnose the potential concerns with resolution ‘Making Mobility Safer and Smarter Everyday.’

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