01661425

Component

Under the NCHRP Project 25-45, acoustic beamforming was used to localize noise sources on heavy trucks operating on highways in California and North Carolina at a total of 20 sites. Over 1,200 trucks were measured under a variety of operating conditions, including cruise on level highways, on upgrades, down degrades, low speed acceleration, and for various speeds and pavements. The acoustic contours produced by the beamforming measurements were used to produce vertical profiles of sound level versus height above the pavement surface. The profiles were normalized to the highest noise level at ground level. The profile averages from each measurement site were found to be independent of speed and operating conditions and were consistent from site-to-site. These profiles were averaged to produce a single profile representing all sites and trucks. For acoustic modeling purposes, the profiles for each ⅓ octave band were approximated using two-point sources, one at ground level and one at a height above the pavement that varies depending on the frequency band of the profile. The upper source heights range from 3.3ft (1m) at 315 Hz to 1ft (0.3m) at 4,000 Hz. For each upper source height, the strength of the two sources varied by frequency. The development and results of these models are presented in this paper and contrasted with those used in the FHWA Traffic Noise Model, TNM®.

This paper was sponsored by TRB committee ADC40 Standing Committee on Transportation-Related Noise and Vibration.

18-02961

English

17p

2018

Transportation Research Board 97th Annual Meeting

Digital/other

Figures; Photos; References; Tables

Acoustic emission; Heavy duty trucks; Height; Measurement; Noise

Environment; Highways; Vehicles and Equipment

Transportation Research Board Annual Meeting 2018 Paper #18-02961

TRIS, TRB, ATRI

Jan 8 2018 10:42AM