A network of siren units will be configured so that the alert signals received in each area of the IRZ are of sufficient volume to be heard distinctly above ambient noise levels in the area.

Community characteristic descriptions, with their associated sound pressure level requirements, are as follows:

a. Uninhabited areas where there are no permanent dwellings, no agricultural land use, and no identified recreation (hunting, fishing, etc.) areas. No alerting is required.

b. Rural areas where single-family housing density is less than 1 dwelling per 100 acres (may include agricultural land use but no recreation areas used by transient populations). Average ambient background noise level is estimated to be less than 30 dBC; therefore, sirens should provide sound pressure level of at least 40 dBC in these areas.

c. Suburban residential areas including primarily single-family housing with density less than 1 dwelling per 5 acres, and which may include agricultural land use or recreation areas used by transient populations, but no significant industrial or commercial activity. Average ambient background noise level is estimated to be 40 dBC; therefore, sirens should provide sound pressure level of at least 50 dBC in these areas.

d. Residential areas consisting primarily of single-family housing with density less than 1 dwelling per 1/4 acre, and with no significant industrial or commercial activity. Average ambient background noise level is estimated to be 50 dBC; therefore, sirens should provide sound pressure level of at least 60 dBC in these areas.

e. Urban residential areas consisting of single- and multiple-family housing with density equal to or greater than 1 dwelling per 1/4 acre, but with no significant industrial or commercial activity. Average ambient background noise level is estimated to be 60 dBC; therefore, sirens should provide sound pressure level of at least 70 dBC in these areas.

f. Commercial/industrial areas where land use is primarily commercial or industrial with daytime population density greater than 2500 persons per square mile or containing major highways or thoroughfares with vehicle counts in excess of 300 per hour for any one hour period. Average ambient background noise level is estimated to be 70 dBC; therefore, sirens should provide sound pressure level of at least 80 dBC in these areas.

[ Chrysler Air Raid Coverage Area ]