Christchurch's 45 tsunami warning sirens may be upgraded as the noise they make does not comply with the national standard.
The Christchurch City Council is looking at options to make them compliant with the national standard.
The council installed the sirens, which are located along the coastline between Brooklands and Taylors Mistake, in two stages between 2012 and 2014.
The sirens are regularly tested to ensure they are working properly however, the noise they make does not comply with the tone set in the National Emergency Management Agency's (NEMA's) Technical Standard.