1.1 ,This specification is for measurement systems used in making sound pressure level measurements in buildings in accordance with ASTM standards and guides. Systems for making sound pressure level measurements in other environments are not addressed in this specification. A future expansion of this specification may include these environments. The systems addressed include one or more microphones and associated components to process the output of the microphone measurement system conforms to a sound level meter specification it is sufficient to specify the category of precision and accuracy required by the measurement system and that direction is given in the user manual for proper use. Where the system is composed of components, specifications are given for microphone type and orientation, filters and windscreens.