Newnes Audio and Hi-Fi Engineer's Pocket Book, 3rd Edition

Public address

Objectives

Intelligibility The first and most important requirement of a

p.a. system is intelligibility. Speech must be heard with clarity,

the syllables distinct, and words readily understood.

Adequate volume Listeners must be able to hear

comfortably without strain or being deafened. In an auditorium,

peaks of around 75 dB A are required, for outdoor events

80 dBA. Where there is high ambient noise such as in a

machine shop, the level must be 10 dB greater than the noise,

but this could take it above the safe hearing limit (see page 4).

High level by itself accomplishes nothing if speech is

indistinct, so volume comes secon ...