Atmospheric absorption conditions for horizontal sound propagation

Atmospheric absorption is important for outdoor sound propagation. Weather changes over the day and the year, and this alters the atmospheric absorption. Thirty years of meteorological measurements from six stations in Sweden were used to determine the conditions for atmospheric absorption. The size of the monthly and daily variances was frequency-dependent. The most accurate information about atmospheric absorption climate is achieved if hourly values over 30 years are used. Errors using I-year hourly data or only the mean values of temperature and humidity for the calculations were determined. Atmospheric absorptions for various parts of the world were estimated. An increase in the accuracy of calculations of outdoor sound levels can be made by taking the local climate into consideration. (C) 1997 Elsevier Science Ltd.