Evaluating project-related noise impacts on sleep in environmental assessments: A proposal to apply decibel adjustments to nighttime noise events based on their time of occurrence over the sleep period time

Health Canada is updating its Guidance for evaluating noise in environmental assessments. Current advice on sleep is drawn from the World Health Organization (WHO) which advises that average noise within the bedroom not exceed 30 dBA, and noise events not exceed 45 dB LAmax on more than 10–15 occasions. Both limits increase by 15 dB outdoors assuming partially opened windows. The WHO’s recommended outdoor nighttime annual average of 40 dBA is also used. Two situations commonly arise: (1) the outdoor annual average sound level is exceeded at baseline; or (2) the number of events during sleep exceeds 15, but are just below threshold. Under these situations, the estimated prevalence of high noise annoyance is applied to protect sleep because it includes a 10 dB nighttime penalty. However, this may not account for the variation in the acoustic threshold that has been observed throughout the sleep period. This paper presents two proposals: (1) apply a decibel adjustment to noise events occurring during periods where thresholds are known to be lower (i.e., the first hour and final 3 h) and/or (2) derive a rating level for estimating annoyance using an alternative nighttime adjustment that splits the night into distinct time periods.Health Canada is updating its Guidance for evaluating noise in environmental assessments. Current advice on sleep is drawn from the World Health Organization (WHO) which advises that average noise within the bedroom not exceed 30 dBA, and noise events not exceed 45 dB LAmax on more than 10–15 occasions. Both limits increase by 15 dB outdoors assuming partially opened windows. The WHO’s recommended outdoor nighttime annual average of 40 dBA is also used. Two situations commonly arise: (1) the outdoor annual average sound level is exceeded at baseline; or (2) the number of events during sleep exceeds 15, but are just below threshold. Under these situations, the estimated prevalence of high noise annoyance is applied to protect sleep because it includes a 10 dB nighttime penalty. However, this may not account for the variation in the acoustic threshold that has been observed throughout the sleep period. This paper presents two proposals: (1) apply a decibel adjustment to noise events occurring during periods...