Technology challenges for New Vehicle Noise Regulations

Current Pass By Noise (PBN) limits of both passenger and commercial vehicles are proposed to be reduced in India, in a phase-wise manner, over a period of next 3 to 4 years, mainly from Environmental Noise Pollution control.

For example, for all passenger cars (M1 category), today's PBN limit of 74 dBA is recommended to be reduced to 72 dBA (phase 1), 70 dBA (phase 2) and 68 dBA (phase 3). And for a Heavy Truck (N3 category whose power is > 250 kW), PBN is recommended to be reduced from 82 to 79 dBA again in the same phase-wise manner.

This will be associated with a revised Method of PBN measurements in line with the latest version of UN-ECE R51:03 replacing the existing Std. IS 3028:1998.

This will definitely make the Environment quieter with growing population of vehicles on road, but there will be great technical challenges before Vehicle Manufacturers as shown below:

Year 2023-24  Noise control solutions existing	Year 2026-27  new technologies needed for Noise control
[1] partial acoustic shielding to power-trains and wheel arch insulations	[a] full encapsulation of power-trains demanding super- efficient thermal mapping
[2] common rail engines with lower rates of combustion pressure rise during vehicle acceleration	[b] alternate propulsion (fuel-cells replacing IC engines) --
[3] gear ratio optimization to balance both drivability and noise radiated by power-trains	[c] intelligent management of vehicles
[4] bigger silencers with resonators & sound-absorbing elements for intake and exhaust	[d] quiet tyres with wheel-covers  producing lower rolling sound on road under full torque
[5] stiff structures & laminated damped panels for non-load carrying members of power-train	[e] higher damping materials for load carrying members of power-train structures
[6] ground gears with higher contact ratios  giving lower drive-whine	[f] active control for tyre/ rolling sound on road
[7] viscous fans for cooling engines of HCVs	[g] active control of exhaust silencer with tunable valves balancing drivability and tail-pipe noise

The above list is not exhaustive; R&D efforts from all Indian OEMs, along with their component suppliers, will continue to search for new Vehicle design solutions balancing all other performance attributes and most importantly, cost of manufacturing.