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The reduction of full acceleration truck pass-by noise conforming to Type ECE-51 regulation (Reference 1) was predicted in a hemi-anechoic chassis dynamometer chamber with microphone arrays and compared with actual test track results. This gave a close match to the track data, with both showing a 4 dB reduction in the A-weighted overall noise level after identical acoustic treatments were applied. Noise control materials were selected to perform as acoustic barriers and absorbers. These were optimized by analyzing the 1/3 octave spectra, determining dominant frequency bands, in critical source locations and engine speeds, and using combinations that dissipate or contain energy well within those bands. With the truck being stationary while tested, important source locations could be quickly identified both subjectively and with localization tools such as Beamforming.

Governmental regulations regarding exterior noise emitted by motor vehicles vary throughout the world. A vehicle which is compliant in one market may not be compliant in another market. In this case, a production North American class 8 truck was being prepared for sale overseas. The requirement to meet European Union (EU) pass-by regulations as tested per the EU standard meant development of a production feasible package to substantially reduce noise emissions without changing any fundamental design or operating parameters of the truck. The development testing was done on a chassis dynamometer in a hemi-anechoic chamber without any specific pass-by noise simulation software. Efforts to develop a reasonably accurate correlation from lab to track, use of acoustic beamforming for source localization and package design iterations leading to a final successful package are discussed.

This paper reports the correlation of truck interior noise, near the driver's right ear, between driving on road and while operating on a dynamometer. It was a critical benchmark in the commissioning process of a heavy-duty truck anechoic chassis dynamometer. It required road load data to be gathered on a Proving Ground, using the Coast Down procedure detailed in SAE J2263 OCT96, and then simulated, while operating the same test vehicle on the dynamometer, using SAE J2264 APR95. The criteria for interior noise comparisons were typical Class 8 driving scenarios: constant high gear cruising, full power single gear acceleration runs, and engine braking. The analyses using these SAE standards, together with the final correlation results, are presented and discussed. A footnote is the unique challenge of Class 8 testing versus SAE coast down procedure, since truck transmissions must not be tested in Neutral, per SAE protocol, to avoid damage.

The objective of this work was to synthesize the time and space average operating airborne noise excitation field from discrete noise sources, to the exterior surfaces of a Class 8 truck cab while operating fully loaded at 60 mph. This noise field was subsequently used as input to a statistical energy analysis (SEA) model, for designing a sound package to reduce interior noise. As a relatively simple and inexpensive alternative approach to direct measurements using a heavy-duty chassis dynamometer in a semi-anechoic chamber, the method nevertheless provided an acceptable input for the SEA development work.

A laboratory technique has been developed for simulating high frequency tyre noise in a car. The technique characterises air-borne tyre noise and its transmission from the tyre and road contact patch to the occupant positions. The technique could be applied to the rapid definition of design modifications in a laboratory environment and the generation of competitive criteria for vehicle benchmarking.