Improvement of signal to noise ratio at outdoor listing position by sound emission timing control over the Internet for mass notification system

Abstract

Mass notification system has multiple nodes, where a node consists of some loudspeakers, in order to cover wide service area. Sound signal is emitted from grouped nodes simultaneously in general. Thus, the simultaneous emission from grouped nodes sometimes makes overlapping of sound signals at a listening point in the service area. Since it affects speech intelligibility, reduction of overlapping is a quite important issue not only for emergency but also reduction of wasteful signal power on mass notification system. Recently,global positioning device and network devices, such as 3G/LTE, become reasonable to be equipped to a node of mass notification system. Therefore, it makes easy to control emission timing at each node intelligently. Development of an intelligent algorithm for mass notification is introduced and a part of the algorithm is implemented on a single board computer, Raspberry PI. Performance on signal to noise ration at all the listing points in service area is presented and discuss it with...