Evaluation of Worst-Case and Mitigation of Pass-By Noise for
                    Commercial Passenger Vehicle under Indian Standard 3028:2023 with Low-Cost
                    Instrumentation

Mohit Gupta

doi:10.4271/2026-01-5071

Stringent environmental noise regulations in India, specifically the transition to IS 3028:2023 (Part 2), have established revised pass-by noise (PBN) limits for commercial vehicles ranging from 74 dB(A) to 75 dB(A) based on gross vehicle weight (GVW) and engine power. Unlike passenger cars, heavy commercial vehicles (HCVs) are primarily driven by diesel engines where powertrain-induced vibration and cooling fan engagement significantly impact exterior noise levels. This study investigates the “worst-case” configuration within a commercial fleet, typically characterized by high gear ratios or unladen drive-away chassis that experience high acceleration rates.

To solve this challenge in a cost-effective manner, a practical and low-cost approach was taken in this study:

Smart Shielding Instead of Vehicle Hardware Changes: Instead of expensive engine/transmission or axle redesigns, simple noise shields were added having sufficient noise absorption capabilities made of basic sound-absorbing foam. By placing these “acoustic blankets” below or around the gearbox, engine block, or wheel arch, the noise was blocked at the source before it could reach the test microphones.
The “Tape and Foam” Strategy: A simple method called masking was used in this study. By temporarily covering parts of the vehicle with a sound-absorbing shield one by one, it could be pinpointed exactly which part was the loudest—like a noisy intake or a vibrating exhaust—without needing costlier lab equipment.
Economical Testing: High-end sensors were swapped with standard handheld sound-level meters and basic global positioning system (GPS) units to track speed and revolutions per minute (RPM) of the engine. Simplified instrumentation and software were used to analyze the frequency pattern generated during the test and thereby reduce the noise from affected components. Otherwise, costlier radar-based instrumentation is required for the evaluation of this revised PBN testing. Many test iterations have been performed on the test track to find the best shield placement before going for the final, official certification.
Worst-Case Identification: To arrive at the worst-case vehicle, multiple vehicles having different lengths and drivelines were tested. The worst case was identified as having the maximum noise contribution during the testing for analysis. This paper emphasizes simplified techniques to bring noise to the specified limit values as per the revised noise standard.