Asia’s largest automotive proving ground uses Simcenter to offer state-of-the-art pass-by noise testing and engineering capabilities

A comprehensive testing track

National Automotive Test Tracks (NATRAX) is a world-class automotive proving ground for the comprehensive testing and evaluation of all vehicle types. It is set on 1,200 hectares outside of Indore, India. The facility is designed to cater to the testing needs of the Indian and Asian automotive industries. It offers many different track designs and surface coatings to test vehicles against varying conditions and terrains. The facility is used to evaluate the functional performance of vehicles with regards to speed, acceleration, breaking, fuel efficiency, noise, vibration, handling, stability, and more. With its vehicle dynamics laboratory, NATRAX is also a center of excellence for vehicle dynamics assessment and engineering.

NATRAX is one of the automotive test centers under the umbrella of the National Automotive Testing and R&D Infrastructures project (NATRiP). NATRiP is an initiative funded by the government of India to support the growing Indian automotive industry. NATRiP invested over $200 million (USD) to create this worldclass facility.

Combating noise pollution to improve public health

One of NATRAX’s primary objectives is to help reduce noise emissions by providing vehicle manufacturers with cutting-edge facilities and services for acoustic engineering. Noise pollution has damaging effects on public health, with consequences ranging from stress and ill-being to impairing cognitive performances, disturbing the human hormonal system, affecting the cardiovascular system and increasing the risk of stroke. Similar negative effects have been observed on the fauna in and near urban or noisy areas.

Road traffic accounts for more than 80 percent of total noise pollution, and as world population rises, so does traffic. Consequently, decreasing noise emission in the transportation industry has become a priority to improve environmental safety with a positive effect on public health.

Dr. N. Karuppaiah is the additional director and site head of NATRAX. In this role, he is tasked with finding solutions for the challenges associated with road transportation, including the necessity for reduced noise emissions.

“Reducing the noise at its source is the most effective noise abatement approach,” says Dr. Karuppaiah. “The complex and pervasive problem of noise pollution has no single solution. It requires a combination of short, medium and long-term approaches and careful consideration of the nature of the noise source.”

State-of-the-art facilities

Pass-by noise testing designates a mandatory procedure which certifies that current and newly developed vehicles do not exceed the noise emission limits sets by local and international rules and regulations. Governments and regulatory institutions worldwide take various actions to safeguard public health and limit the impact of traffic growth and the resulting noise pollution. They set legislation and impose norms on vehicle noise emissions which lower acceptable noise level limits for both vehicle pass-by and tire rolling noise levels. These norms include pass-by and coast-by noise testing procedures as prescribed by the International Standards Organization (ISO). These tests are regulated mainly by the United Nations Economic Commission for Europe (UNECE), which promotes global harmonization of vehicle regulations. Apart from maximum noise levels for combustion engine vehicles, minimum noise levels are imposed for hybrid and electrical vehicles. These make a very limited amount of noise at low speeds and impose safety risks for bicycle riders and pedestrians, especially children and the visually impaired.

NATRAX’s noise testing track is split into two surfaces. The first surface is complaint to ISO 10844:2014 and the second surface to ISO 10844:1994. Both surfaces used to homologate vehicles according to the widely used ISO 362-1 pass-by noise testing standard and its regulatory counterpart UNECE Regulation 51.3. The second surface is designed to certify vehicles according to the standard’s latest revision. Both test surfaces are standards compliant in terms of surface homogeneity, texture depth, residual void content and noise absorption coefficient. The entire track series has lighting arrangements to allow night testing when temperatures are within range of the standards and environmental background noise is typically at its lowest.

“Testing is an essential step in the process of developing new vehicles, from their components to their full systems,” says Dr. Karuppaiah. “In India, the availability of appropriate testing facilities was limited and not aligned with the rising demand from the vehicle and component manufacturers. This was a bottleneck for the development of the local transportation industry. The new full-fledged proving ground now covers the testing needs of all types of vehicles, from two- and threewheelers to passenger and commercial vehicles.”

With regards to noise abatement, the testing facilities include world-class passby noise testing tracks, helping manufacturers comply with the latest standards and regulations.

The track is used for development and homologation testing according to the applicable standards for pass-by noise testing. It is also employed to perform vehicle interior noise, rolling noise or stationary noise measurements. The passby noise tests measure noise emitted as the vehicle passes by the microphones at a given speed, gear and acceleration ratio. Precise evolution of overall levels in function of vehicle position, speed and acceleration are calculated according to the standards. The next step in pass-by noise engineering is determining the source contribution to the pass-by noise levels. This includes interior noise test measurements that can be performed simultaneously with pass-by noise tests, such as the noise at the driver’s and passenger’s ear level, and rolling noise measured at the tires while a vehicle is decelerating with the engine off and the gears disengaged. Finally, the stationary noise test is measured with microphones by the vehicle exhaust as the operator revs the engine to higher rotations per minute (rpm).

The NATRAX test tracks are designed to support the flawless execution of all these tests according to various national and international standards. They are equipped with leading-edge equipment to perform accurate measurements, including light barriers, weather station, microphones, and Siemens Digital Industries Software’s Simcenter™ SCADAS data acquisition hardware and Simcenter™ Testlab™ analysis software.

“Simcenter Testlab gives us a very detailed, user-friendly reporting structure,” says Sagar Bendre, project engineer, NATRAX. “It builds the standard procedures which guides us through the testing processes but also offers additional information on the vehicle’s aggregate noise performance beyond a simple ‘pass’ or ‘fail.’”

Pass-by noise testing procedures

Accurate exterior pass-by noise measurements require reliable equipment and a systematic approach. Measuring by using sound level meters, for example, would yield results that may not account for vehicle and atmospheric parameters or monitor the test conditions.

“We have been recently equipped with a complete pass-by noise testing system from Siemens to perform accurate, quick, repeatable and reliable measurements,” says Dr. Karuppaiah. “We are now able to monitor all parameters comprehensively as per the requirements. In the near future, we are considering placing permanent pass-by noise testing equipment on the test track. Where manufacturers need to perform more tests in a shorter timeframe, we will upgrade our track equipment to allow for continuous testing of vehicles.”

Revised pass-by noise procedures make testing more challenging and create the need for better data management and more user guidance. More precise driver guidance, for instance, has become paramount. This contributes to maximizing the number of successful, valid pass-by noise test runs. The Simcenter™ Testlab™ Driver’s Aid App gives clear, unmistakable instructions to the vehicle driver to make sure the acceleration starts at the right position and at the correct speed.

In the future, the Simcenter multi-vehicle pass-by noise solution will enable NATRAX engineers to perform more tests per day, with multiple vehicles being driven simultaneously. In this robust configuration, each vehicle is equipped with its own measuring system and a laptop. Simcenter SCADAS Pass-by noise software uses a global positioning system (GPS) sensor to measure vehicle speed. All data is recorded with GPS-based absolute time stamping for later synchronization. Multiple sets of microphones are connected to a trackbased Simcenter SCADAS system. After each measurement, data from the vehicle and track systems are merged using GPS absolute time stamping and are directly processed into results and an overview report for the driver. Thanks to the multiple pairs of microphones, Simcenter Testlab software can automatically select the one at which the speed is closest to the target center speed. This helps obtain repeatable results and greatly increases the success rate of a test.

Beyond homologation

Fast and accurate homologation results are not the only outcome of vehicle acoustics tests at NATRAX. While powertrain noise remains the main contributor to the overall exterior noise level of internal combustion engine vehicles, noise abatement efforts increasingly focus on reducing tire noise.

New requirements have been set by the Indian government concerning tire rolling noise levels, tire wet grip and rolling resistance. NATRAX’s facilities shall offer both the vehicle and tire industries a one-stop solution for all of their noise, vibration, and harshness (NVH) benchmarking and testing needs. NATRAX’s pass-by noise testing facilities support this with the UNECE Regulation 117 tire noise testing standard.

“NATRAX’s ambition goes beyond offering state-of-the-art reliable service and facilities for vehicle and part homologation,” says Dr. Karuppaiah. “The analysis capabilities of Simcenter Testlab software brings deeper engineering insights into the NVH behaviour of vehicles. Advanced transfer path analysis techniques such as acoustic source quantification allow engineers to identify, quantify and rank the contributions of separate subsystems, such as intake, powertrain, exhaust, tailpipe and tires, to the overall pass-by noise level. Those techniques are efficient troubleshooting tools for noise reduction; they are also employed for precise target setting early in the design process.

“With our facility, equipment and expertise, we are confident that we offer the industry the toolset it needs to make the world a quieter place.”