ISO 9921-1:1996

Ergonomic assessment of speech communication — Part 1: Speech interference level and communication distances for persons with normal hearing capacity in direct communication (SIL method)

Provides a method for prediction of the effectiveness of speech communication in the presence of noise generated by machinery as well as in noisy environment. Parameters are the ambient noise at the speaker’s position, ambient noise at the listener’s position, distance between the communication partners and a great number of physical and personal conditions.