Technical Booklet G Resistance to the Passage of Sound·Page 119·B2.11
Test room volume requirements
Test rooms should have minimum volumes of at least 25 m³; if this is not possible, the actual volumes used must be reported.
Section 1 gives guidance on the room types that should be used for testing. These rooms should have volumes of at least 25 m3. If this is not possible then the volumes of the rooms used for testing should be reported.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet G - Resistance to the Passage of Sound.pdf