The future of bus transit in new millennium is promising. This optimism is based on an anticipated long-term slowdown in growth of suburbs and revitalization of central cities. It reflects and escalates the public concern with traffic congestion, sprawl and pollution. This calls for double the use of public transport to address above issues. It calls for changing the mind-set of society towards public transports like buses, coaches etc. This could happen if bus design ensures right comfort, safety and TCO by ensuring refined bus transport. Hence, it is responsibility of OEMs to provide the new generation buses and coaches, which will ensure the public demands of comforts in terms of NVH refinement.
This paper covers the unique approach used to convert the existing bus NVH refinement to next level as a short-term solution and with the intention of articulating NVH strategies for new generation bus development. This work explains combined experimental and simulation approach deployed through advanced signal analysis tools, root cause analysis, source ranking and identifying the major potential sources. Vehicle measured with non-linear noise patterns, boom noise, inferior sound quality parameters and high tactile and floor vibrations. This was because of common chassis platform, common engine mount system, driveline system and clutch system for trucks and buses and the absence of acoustic material in different part of body. CAE analysis was carried out to identify structural weaknesses and resonances in chassis and power train as these were major transfer paths for higher in cab noise and vibrations.
With all potential solutions updated on vehicle, it was found that cabin noise improved by 6-7 dB (A), articulation index improved by 20-25% and vibration improved about 70% at all load conditions. The bus was successfully demonstrated to juries for reduced noise and vibration levels and confirmed for class leading NVH refinement levels. It was possible with improvement in bus manufacturing processes, critical to quality component and subsystems for NVH improvement with minimum cost impact.