01590668

Monograph

http://www.trb.org/Main/Blurbs/173858.aspx

This research studied the change in sound levels and characteristics caused by sound reflections off a reflective (non-absorptive) noise barrier on the opposite side of a highway. The analysis was done using measurements at five barrier sites and adjacent sites without a barrier under equivalent site, source, and meteorological conditions. Changes in broadband and 1/3 octave band equivalent sound levels (Leq) were studied, along with statistical descriptors, particularly the L₉₀ and L₉₉ metrics. Evidence is seen of increased Leq both across the road from the barrier and at positions between the road and the barrier. In some cases, even greater increases in L₉₀ and L₉₉ suggest a sustaining of the received sound due to the reflections. Spectrograms, visualizations of the spectral time history, reveal that the presence of the barrier causes sound levels to increase over a broad range of frequencies and causes higher sound levels to be sustained for a longer period of time. Psychoacoustic metrics were calculated and combined into three measures of annoyance. Annoyance metrics opposite the barrier tended to increase relative to the No Barrier site in lighter traffic where individual vehicle pass-bys are distinct.

NCHRP Project 25-44

English

428p

2016

NCHRP Web-Only Document

9780309439633

Contractor's Final Report

Digital/other

Appendices; Figures; References; Tables

Field studies; Noise barriers; Noise control; Sound level; Sound transmission

Environment; Highways; I15: Environment

TRIS, TRB, ATRI

Feb 19 2016 2:21PM