These guidelines cover the measurement of sound pressure levels in buildings from all sources; they supersede both Part 1 and Part 2 of the ANC Guidelines for measuring noise in buildings, which are withdrawn. Since the ANC guidelines were first written in 1997 and 1998, International Standards and other guidance have been published that cover measurement of sound in buildings from a variety of sources and frequency ranges. However, measurement of sound inside buildings from general external sources has not received much attention. These guidelines aim to help the reader find an appropriate method for the measurement task in hand; where there is a lack of other formalised guidance, a simple measurement method is proposed that may be appropriate. Measuring sound within buildings can involve many more complications than are present for external measurements. The simple method proposed may not be appropriate for every situation, but aims to assist in the development of a suitable, bespoke approach. All the methods described in these guidelines are intended to be used by consultants with suitable skills, knowledge and experience in sound level measurements and who are familiar with the appropriate equipment.