Page 28 - Spring 2009

American National Standard Quantities and Procedures for Description and Measurement of Environmental Sound—Part 6: Methods for Estimation of Awakenings Associated with Outdoor Noise Events Heard in Homes has just undergone major revisions that culminated in the new standard pub- lished last year. Based on the work by Anderson and Miller,12 this standard now provides a means to predict the probabili- ty of awakening to an ensemble of events distributed in any fashion throughout the night.
Method based on probability of awakening
The method determines the number of people or percent of the population likely to be awakened at least once from a full night of noise events. Most sleep disturbance data are reduced to a relationship of the form of a dose-response curve similar to those shown in Fig. 1. The Federal Interagency Committee on Aviation Noise recommends a functional relationship for subjects newly experiencing the noise of night-time discrete events.
(1)
where PA,single is the probability of being awakened by a Sound Exposure Level of LAE
Such relationships cannot be applied directly to deter-
mine awakenings that may result from a full night of noise events. However, such a dose-response relationship can be used to determine the probability that a single event will pro- duce an awakening. This probability may then be converted into a probability of NOT being awakened (1 minus the prob- ability of being awakened). Next, the probability of NOT being awakened all night by multiple events is computed as the joint probability of not being awakened by any of the night-time events. Finally, the probability of being awakened at least once by any of the night-time events is one minus the probability of not being awakened at all. Equation (2) expresses this approach.
(2)
where:
a = index across all N noise events during the night,
and
Pawakesingle is the probability of being awakened by the nth sin- gle event.
Therefore, if Fig. 1 gives the probability of awakening an
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