Provisions to control unreasonable noise emissions include the ability to establish and, if appropriate, require compliance with rules setting permitted noise levels. This includes the Christchurch City Council’s City Plan (May 1995), which has rules with noise level standards. These restrictions form part of controls pursuant to the Resource Management Act 1991 designed to maintain the peaceful amenity of residential neighbourhoods – an important environmental health consideration. If standards in the City Plan are to effectively maintain acoustic amenity then they should not be significantly louder than ambient sound levels. As ambient sound levels significantly vary over a day the applicable standards should reflect such variation. An investigation examined ambient daytime sound levels in Christchurch’s residential areas. In particular consideration was given to the possibility that ambient noise levels reduce during the early evening period (1800 to 2200 hours) so as to warrant an adjustment of the applicable standards during that period.