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23 Nearly every aspect of aviation, and related technology, has changed since the 1985 publication of FAAâs Aviation Noise Effects. Although much has been learned, both technically and socially, the process of identifying, quantifying, and alleviating noise effects of aviation remains an art. We now know that because aviation noise does not approximate those of occupational health criteria, hearing loss is unlikely; avia- tion noise effects do not influence newborn birth weight, and annoyance may be largely influenced by non-acoustic factors. Sleep interference, with great variability between laboratory and in-home studies, occurs much less than previously thought. We have also learned that cross-sectional studies are notori- ously difficult to interpret, often report conflicting results, and do not result in dose-response relationships. Investigations that report a distinct percentage of the population who are âhighly annoyedâ at any given day-night average noise level may be incorrectly interpreted as having a more precise meaning than should be taken from the data. Areas of annoyance that remain to be investigated include the relationship between single-event noise levels and annoy- ance. Use of data not previously available, including airport noise monitoring systems, flight tracking systems, and geographic information systems, may prove to be a rich source of data in understanding annoyance and meteorologi- cal and topographical effects. Aviation noise effects on schools and school children have been well-researched and documented. Recent studies indicate a potential link between aviation noise and both reading comprehension and learning motivation, particularly for those children who are already scholastically challenged. Other studies indicate increased stress levels for children in high-noise environments. New best practices designs for interior classroom acoustics and speech intelligibility have been completed, but do not address intermittent noise such as aviation noise. Some research has indicated that effects of aviation noise may differ from the effects of other transporta- tion noises. Speech interference, although quite important, has not had the benefit of research as related to intermittent noise sources. New definitions and criteria for natural soundscape in national parks and Native American tribe lands are being established, and new dose-response relationships may be used to guide important policy decisions. Low frequency noise with its related vibration, meteorological, and topological data con- tinue to drive modeling improvements, and correct some lim- ited under-predictions of sideline-noise levels. Home property values may have limited relationship to noise levels, and future research linked with powerful geographic information system tools may provide new insights. Although long-term averages are typically used in conjunction with land use planning and residential property location, new research indicates that the use of Leq (equivalent sound level) may display a greater accu- racy in identifying areas most affected by aviation noise. In conclusion, despite decades of research and new, well- documented information, aviation noise effects continue to be an enigma waiting to be solved. CHAPTER THIRTEEN CONCLUSIONS
