Community Noise Impact Planning for a Very Large Wind Tunnel

Abstract

A study was conducted to determine community impact of noise from a large intermittent wind tunnel to be located in a predominantly rural area near several small cities. Acoustic power output will be up to 208 dB, with each run lasting 3 sec. Because run schedule and acoustic power for each run will be variable, noise impact was expressed in terms of the Noise Exposure Forecast (NEF) scale. An important part of this study was to determine noise standards whereby genuine good relations may be maintained with surrounding residents. The generally accepted NEF = 30 used near busy urban airports could not be automatically assumed for the rural community under consideration. It was therefore necessary to examine noise impact and establish limits appropriate to a quiet rural community. Data on the interference of residential activities by noise were reviewed. Based primarily on sleep disturbance and speech interference, nominal limits of NEF = 15 for residences and NEF = 5 for hospitals were determined. It was found that these limits will be generally met for average anticipated facility utilization. However, certain marginal areas exist and unacceptable levels can result under adverse meteorological conditions. Alleviation of these problem areas can be achieved by careful scheduling of facility usage. It was noted that NEF contours for an arbitrary run schedule can be related to NEF for a reference schedule through a factor representing run frequency and intensity. A nomogram was devised so that facility operating personnel can obtain this factor easily for any planned schedule. [This work was performed under Contract No. F 40600-72-C-0007.]