Some Christchurch residents are calling the city's new tsunami warning system a "dud'' after today's test.

The first test of the Christchurch City Council's 22 tsunami sirens was held at 11am.

The $550,000 sirens had been installed on the coastline between Waimari Beach and Sumner.

Some residents reported on social networking sites that the sirens sounded "faint", and some said they could not hear them at all.

However, Civil defence and emergency management manager Murray Sinclair said the sirens were only meant to be heard up to 600 metres away from the coast, and were not designed to penetrate walls.

"We had volunteers around; some of the feedback they've picked up is that some people just couldn't hear it at all, or only just ... but if you were outside, you heard it fine."

The sirens were set at 85 decibels, which was the balance between having as many people hear it as possible and preventing anyone nearby from suffering hearing damage, Sinclair said.

It was also designed to start off quietly, with the volume increasing in three stages.

Those who did hear the siren were encouraged to check on their neighbours, especially those who were elderly or had a disability, Sinclair said.

The sirens would be tested twice a year from now on - when daylight saving ends and beings - so residents are able to identify the sound of the siren and know when to evacuate the coastal area.

If the sirens were activated for more than 10 minutes, it was not a test and residents should evacuate the area.

The system would not be used for a local tsunami, but could be used in a regional one.

The council was also asking Christchurch residents to provide feedback on the testing, by filling out an online survey.

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