USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Acoustical Warning Device for Locomotive Horns

Document Series
Technical Reports
Federal Railroad Administration
Report Number
Subject Grade Crossing Technology
Acoustic Warning Device, AWD, air horn, variable directivity, grade crossing, sound beam steering, speaker array, locomotive, detectability, noise reduction

This report summarizes the research and development of a variable directivity Acoustic Warning Device (AWD) used as a locomotive horn. A Global Positioning System (GPS) was developed to control an arrangement of directional loudspeakers. Loudspeakers are arranged on the locomotive so that sound is directed forward when the horn is initially sounded 1/4 mile from a grade crossing. Other loudspeakers are sounded approaching a crossing to direct sound more to the wayside. This approach reduces wayside noise and maintains horn detectability. The work took place at the Transportation Technology Center (TTC) with wayside sound levels comparing well to predicted patterns.

Last updated: Friday, February 11, 2022