Agenda - 11-22-2004-c1 - Laserfiche WebLink

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24 Attachment 3 Environmental Sound Page 9 Sleek Interference ~ ~ .l [ Sleep interference is a consistent and prevalent complaint in surveys taken about community noise problems, Research reviews clearly show noise interferes with sleep either by awakening the sleeper, by altering the depth of the sleep, or by making it difficult to go to sleep, It is accepted that steady noises of a given level are not as disturbing as intermittent noises of that level. However, a complicating factor in research is that meaningfulness of the noise has an effect on whether or not a person is awakened. For instance, the cry of a baby may awaken a concerned mother but not others, Undesired sound including information such as speech or music is difficult to ignore when one is trying to go to sleep. A developed attitude about a noise also influences ability to go to sleep. A person upset by sound fiom a neighbor's au conditioner may have difficulty going to sleep. However, the same person may have no problem with a very similar sound from his own ventilation system at other times. Older people aze more likely to be awakened, but aze less affected by the loss of sleep, There is widespread consensus that steady sound levels in bedrooms should be below 47 dBA. Lower levels are desirable as long as they are steady, Key factors are to prevent changes of 10 decibels or more in sound level, or intermittent sounds over about 55 dBA. A higher level of steady sound, less than 47 dBA, can help mask intermittent sounds that would be a problem with lower steady sound levels, Community Reaction and Annovance The adverse responses of people to noises introduced into their environment are measured in two ways, These are counting complaints to autlrorities or"communityreaction,"and bysurveys that rate "annoyance." The number of complaining people does not directly indicate annoyance. Some people who aze annoyed do not complain.. One study examined the relationship between the number of people "highly annoyed" and the number who complained, The reseazchers found that if 1 % complained, 17% were highly annoyed, and if 10% complained, 43% were highly annoyed. A few complaints may show a high community- annoyancelevel. As a result of various research studies, several important factors were identified for determining the community reactionand annoyance produced by noise. These were identified by the US EPA as follows. Level and frequency content of the noise. Duration of the noise, Time of day noise occurs, Time of year the noise occurs, History of prior exposure to the noise source, Perceived attitude of the noise source owner,