Vehicle pass-by noise
Characterizing the overall acoustic signature of a vehicle requires measuring it in operation – as it passes stationary microphones.
The external sound of a moving vehicle is part of its character and can be an essential part of its appeal. But the collective traffic noise from thousands of cars and trucks can be considerable. To help reduce noise in our environment, government agencies set pass-by noise limits for each type of ground vehicle – critical regulations that must be respected.
Characterizing the overall acoustic signature of a vehicle requires measuring it while in operation – as it passes by stationary microphones. To measure vehicle noise in circumstances that most accurately reflect the vehicle’s real use, measurement standards stipulate how noise must be measured. The methods for wheeled vehicles like trucks, automobiles and motorbikes dictate the precise position where the test vehicle must be accelerated at full power, with a wide-open throttle. Similarly, aircraft-certification tests require take-off and landing-noise measurements.
Pass-by noise development
Since it is an intensely standardized area, it’s important to stay abreast of the latest developments in pass-by testing. A good example is the additional sound emission provisions (ASEP), which increase the amount of tests for vehicles and considerably deepen the complexity of calculations. Another is indoor pass-by, which can save expensive time on a test track but is subject to its own particular measurement standards. Our software helps guide you through all of the required testing steps for the relevant standards within your industry.
Pass-by noise measurement is mandatory for automotive manufacturers for product certification and the measurement procedures and conditions are recommended by international standard, ISO 362-3. In addition, pass-by noise measurements can be used as a product development and troubleshooting tool.
PULSE Indoor Pass-by provides a tool for simulating field pass-by performance for a vehicle running on a chassis dynamometer in a hemi-anechoic test chamber according to a range of international standards. Measuring a vehicle’s interior and exterior noise during operation is far simpler in such a chamber. Eliminating variables such as weather and site variations makes measurements more reproducible, while the stationary vehicle allows more instrumentation. Simulation of normal pass-by noise is achieved by placing a row of microphones alongside the test vehicle so that there is no need to drive the test vehicle past stationary microphones as is standard in a conventional outdoor pass-by measurement. Instead, the vehicle is accelerated in the same way on a chassis dynamometer.
A typical Indoor Pass-by system is based on the PULSE LabShop data acquisition and analysis platform. The software components — PULSE Indoor Pass-by — are combined with LAN‐XI data acquisition hardware (including frame, modules and front panels), free-field microphones and a data recorder.
The Exterior Noise Contribution Analysis option gives further possibilities for identifying the major contributions of exterior noise corresponding to the specific noise sources, for example, powertrain, intake/exhaust system and tyres.
Certifying that vehicles comply with noise emission specifications requires measuring according to procedures defined by international standards. These specify a test of powertrain and tyre/road noise under typical urban traffic conditions, putting stringent demands on pass-by and coast-by noise testing.
Test equipment must support the specialized measurement methods and validate the defined values dictated by the test standard. Our solutions cover the full spectrum of pass-by testing – from simple conformance testing to multi-channel diagnostics. All of our pass-by solutions (outdoor or indoor) support the most common international standards, including ISO 362, SAE J1470, ISO 13325 and ISO 5130. In addition, our beamforming array selection provides outdoor sound mapping, helping to accurately locate the sound sources that contribute to the vehicle’s sound.
The PULSE vehicle pass-by solutions are complete PULSE data acquisition and analysis platforms. They include LAN-XI data acquisition hardware, pass-by related accessories (such as photocells) for giving absolute position reference, a speed sensor (radar, GPS or other device) for providing continuous speed and position information, and a weather station for providing environmental parameters. The system is scalable, ranging from conformance test configurations to multi-vehicle configurations with on-board vehicle measurement channels. Single-person operation is also supported.
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