Physiological And Psychological Effects Of Aircraft Noise The physiological and psychological effects of noise vary widely among individuals. Response to noise is also strongly affected by the nature of the noise source. Voluntary exposure can be used to refer to sound or noise over which the recipient has complete control. Workplace noise exposure is semi-voluntary. Except for aircraft passengers and those employed in the aviation industry, aircraft noise exposure is involuntary. Voluntary exposure to sounds, workplace noise exposure, and involuntary noise exposure produce different psychological effects. Damage To Hearing The Environmental Protection Agency (EPA 1974, 1978) has identified a protective noise level limit on the basis of hearing loss due to long time exposure. The identified level is a 24 hr/day, 365 day/year equivalent sound level Leq = 70 dBA which would protect 96% of the population from significant hearing loss. Exposure to higher levels could produce more than 5 dB of hearing loss at a frequency of 4000 Hertz in some of the population. Consider the population outside of the day-night noise level contour DNL70 (based on aircraft noise alone). Assume outdoor activities average not more than 7 to 8 hours per day. Then, aircraft noise would contribute no more than 50% of the energy to reach an equivalent sound level Leq = 70 dBA for that population. We can then conclude that, with few exceptions, aircraft noise exposure makes a small or negligible contribution to hearing loss in the study area. Those with aircraft noise exposures that might exceed the protective noise level limit include individuals who reside or spend substantial amounts of time within day-night noise level contour DNL70. Aviation industry employees who work outdoors comprise a substantial portion of that group. Speech Interference Sentence intelligibility (i.e., identifying words in context) in a typical living room, assuming a speaker using a normal voice level, and a listener with normal hearing may be related to noise level as follows: Indoor sentence intelligibility % 80 95 99 100 Steady background noise level dBA 69 64 54 45. Intelligibility of individual words or numbers is less than 100% at a steady background noise level of 45 dBA. Sentence intelligibility is about 95% at 3 meter speaker-to-listener distance outdoors with a steady background noise level of 45 dBA. DNL is an energy average (with nighttime weighting) based on noise levels in dBA. A typical aircraft noise-vs-time pattern consists of a series of noise events throughout the day and night. At DNL = 45, there will be many events with noise levels far exceeding 45 dBA in a typical aircraft noise-vs-time history. Thus, at DNL = 45, there will typically be many intervals of speech interference. Sleep Interference Sleep is crucial to health, and noise causes sleep interruption. Using information from the FAA (1977), one can estimate the percentage of residents disturbed as a function of aircraft-generated noise exposure. At DNL=65, the approximate percentage of residents subject to sleep interference is: 46% startled 44% awakened 27% have rest or relaxation disturbed 24% kept from going to sleep It is difficult to evaluate the exact effect of outdoor noise on sleep. Individuals vary widely in sleep habits, building attenuation varies, and aircraft noise patterns vary as well. Effect Of Aircraft Noise On Children’s Health Evans (1998) reported on a study of 217 rural 3rd and 4th grade school children living near Munich. The group was assessed 6 months before and 6 and 18 months after the opening of an airport. About half of the group lived under a flight path. Modest but significant increases in blood pressure were found in the noise-exposed group. Evans said that the results of this study may predict greater likelihood of higher blood pressure throughout adulthood. Effect Of Aircraft Noise On Learning Powers (1993) reports that Gary Evans compared abilities of children from schools in quiet neighborhoods with those from four neighborhoods near Los Angeles County Airport. The study found that children from schools near the airport had diminished reading skills, gave up more quickly, and failed more often to solve puzzles. The study concluded that children may learn to cope with noise by tuning it out. Then, children may begin to tune out all auditory stimuli. It is assumed that poor auditory processing leads to reading problems. The Federal Interagency Committee on Aviation Noise, (FICAN, 1998) also examined research on the effects of aircraft noise on school-age children. FICAN decided against action at this time. |