NCJ Number
48084
Date Published
1978
Length
55 pages
Annotation
A SIREN USING A STRONG NARROW BEAM OF SOUND IN THE FORWARD DIRECTION FOR OPEN HIGHWAY USAGE AND A BROADER BEAM FOR USE NEAR ROADWAY INTERSECTIONS IS DISCUSSED.
Abstract
THE NATIONAL BUREAU OF STANDARDS HAS DEVELOPED A DUAL-MODE DIRECTIONAL ELECTRONIC SIREN WHICH CAN BE ELECTRICALLY SWITCHED UNDER MANUAL CONTROL FROM A STRONG NARROW BEAM OF SOUND TO A BROADER BEAM. THE INTENSE BEAM OF SOUND IS PRODUCED BY A VEHICULAR ROOF-MOUNTED BROADSIDE ARRAY CONSISTING OF FOUR COMPACT COMMERCIAL 100-WATT ELECTRONIC SIREN LOUDSPEAKERS SPACED 15.2 CENTIMETERS (6.0 INCHES) APART. TWO ELECTRONIC SYSTEMS WERE DEVELOPED TO BROADEN THE INHERENTLY NARROW BEAM OF THE BROADSIDE ARRAY. ONE SYSTEM SWEPT THE BEAM FROM SIDE TO SIDE. THE SECOND SYSTEM INVOLVED THE USE OF A FILTER NETWORK. A-WEIGHTED SOUND PRESSURE LEVEL MEASUREMENTS MADE IN AN ANECHOIC CHAMBER AND OUTDOORS ON A VEHICLE SHOWED THAT THE MAXIMUM SOUND PRESSURE LEVEL OF THE DUAL-MODE SIREN IS 7 TO 10 DECIBELS HIGHER IN THE DESIRED DIRECTIONS THAN A SINGLE 100-WATT COMMERCIAL ELECTRONIC SIREN. REFERENCES AND A GLOSSARY ARE INCLUDED, AND THE APPENDIXES CONTAIN A DESCRIPTION OF THE SYSTEM, REASONS FOR CHOOSING A BROADSIDE ARRAY AND DESIGN FOR NATIONAL BUREAU OF STANDARDS SYSTEM 2 DUAL-MADE DIRECTIONAL SIREN, AND CIRCUIT DIAGRAMS FOR NATIONAL BUREAU OF STANDARDS SYSTEM 1 AND 2. (AUTHOR ABSTRACT MODIFIED)