100 mm

ELECTRO-TECHNOLOGY FOR INDUSTRYTechnologyPlanning audible signalingIn order to determine the acoustic alarm, it is important to know the’starting value’ (existing ambient noise level) and the ‘target value’ tobe calculated.According to the EN ISO 7731 standard (replacement for EN 457),a sounder should have a minimum sound level of 65 dB (A).StandardMinimum differenceto the ambient noiselevelApplicationEN ISO 7731 at least 15 dB (A) Public areas and workplacesDIN VDE 0833EN 60849at least 10 dB (A)Fire alarm (in fi re alarm systems)Evacuation signal (in alarm systems)From a required sound level of 110 dB (A) upwards, it is recommendedto use visual signaling devices in addition to acoustic alarms.Example calculationThere are various possibilities of achieving 82 dB (A) for an area of 50 x 30 m:1 x 120 dB (A) or 10 x 100 dB (A) sounders are required.Sound transmission area of a 100 dB (A) sounder in order to achieve 82 dB (A) = 200 m 2Sound transmission area of a 120 dB (A) sounder in order to achieve 82 dB (A) = 20,000 m 2100 dB (A)120 dB (A)82 dB (A)The type of signaling (number of sounders) used is essentially determined by the geometric properties of the room,the shape of any obstructions and the maximum permissible sound pressure level of the sounder. When using asounder with, for example, 120 dB (A), it must be ensured that people cannot be in the near vicinity of the sounder.If this is not possible, a divided installation should to be chosen.29