Laserfiche WebLink
City of Santa Ana -Park View at Town and Country Manor <br />Draft EIR Noise <br />just detectable difference in most situations. A 5 -dB change is readily noticeable, and a 10 -dB <br />change is considered a doubling (or halving) of the subjective loudness. A 3 -dB increase or decrease <br />in the average traffic nose level is realized by a doubling or halving of the traffic volume, or by about <br />a 7 -mile- per -hour increase or decrease in speed. <br />For each doubling of distance from a point noise source, the sound level will decrease by 6 dB. In <br />other words, if a person is 100 feet from a machine and moves 200 feet from that sound source, sound <br />levels will drop by approximately 6 dB. Moving 400 feet away, sound levels will drop approximately <br />another 6 dB. For each doubling of distance from a line source, such as a roadway, noise levels are <br />reduced 3 to 5 decibels, depending on the ground cover between the source and the receiver. <br />Noise Exposure <br />An interior CNEL of 45 dB is mandated by the State of California Noise Insulation Standards (CCR, <br />Title 24, Part 6, § T25 28) for multiple - family dwellings and hotel and motel rooms. In 1988, the <br />State Building Standards Commission expanded that standard to include all habitable rooms in <br />residential use, including single - family dwelling units. Since normal noise attenuation within <br />residential structures with closed windows is about 20 dB, an exterior noise exposure of 65 dB CNEL <br />allows the interior standard to be met without any specialized structural attenuation (dual -paned <br />windows, etc.). A noise level of 65 dB is also the level at which ambient noise begins to interfere <br />with one's ability to carry on a normal conversation at reasonable separation without raising one's <br />voice. Table 4.5 -1 summarizes typical noise sources, levels, and responses. <br />Table 4.5 -7: Noise Levels and Human Response <br />Michael Brandman Associates 4.5 -3 <br />H\Cl t(P RnJ 327b327003MMVB270030 Sec01 Noi�.doc <br />Noise Source <br />Noise Level dBA Response <br />30 Very quiet <br />Library <br />Refrigerator humming <br />40 <br />Quiet <br />Quiet office <br />50 <br />Quiet <br />Normal conversation <br />60 <br />Intrusive <br />Vacuum cleaner <br />70 <br />Telephone use difficult <br />Freight train at 50 feet <br />80 <br />Interferes with conversation <br />Heavy -duty truck at 50 feet <br />90 <br />Annoying <br />Jet takeoff at 2,000 feet <br />100 <br />Very annoying-, hearing damage at sustained <br />exposure levels <br />Unmuffled motorcycle <br />110 <br />Maximum vocal effect-, physical discomfort <br />Jet takeoff at 200 feet <br />120 <br />Regular exposure over one minute risks <br />permanent hearing loss <br />Shotgun firing <br />130 <br />Pain threshold <br />Carver jet operation <br />140 <br />Harmfully loud <br />Source: Melville C. Branch and R Dale Beland, Outdoor Noise in the Metropolitan Environment, 1970. <br />Michael Brandman Associates 4.5 -3 <br />H\Cl t(P RnJ 327b327003MMVB270030 Sec01 Noi�.doc <br />