Feasibility of a Train Horn with Optimized Directivity: Environmental and Occupational Noise Benefit of an Ideal Train Horn
This report examines the feasibility of and recommends an acoustical specification for such an optimized horn. The detectability of the horn signal for motorists inside vehicles, the areas of environmental noise impact and occupational noise exposure have been compared for the optimized horn and several typical standard horn systems. It has been found that detectability could be improved and noise impact area reduced by 50 percent or more, depending on amplitude. The optimized horn must have a variable directivity pattern that dynamically changes as a function of train position relative to the crossing to provide substantial noise reduction. Current acoustic source technologies which generate directional sound are examined including “acoustic hailing devices”—a recent technological advancement typically used for military applications, naval communication, and crowd control. Capable of focusing high amplitudes of sound within a narrow beam, acoustic hailing devices have been identified as a feasible means of meeting the required specifications. Finally, the study provides general information concerning cost and implementation of the device.