Should a tsunami strike the Coromandel Peninsula locals should not be solely reliant on warning sirens, says the Thames Valley Civil Defence.

Last week tsunami sirens throughout the peninsula were activated as part of Civil Defence's annual testing of the system.

Anxious locals have reported they failed to hear Coromandel's tsunami sirens which were tested last week.

But many locals have been left feeling anxious after reporting they did not or could not hear the sirens when turned on.

TVCD manager Gary Talbot says aside from sirens in Matarangi which did not operate correctly, every other system functioned properly.

'We have received reports from a number of people to indicate that they didn't hear the siren.

'This is the issue of sirens, many mitigating factors such as back ground noise or wind direction affects their audibility.

'The current position of Civil Defence is the type of sirens used on the Coromandel is not recommended because there are limitations.”

There are about 20 sirens dotted along the Coromandel coastline, with most being installed at the request of local communities.

When activated the noise emitted by the siren goes up and stays up until danger has passed and they are switched off.

Gary feels the sirens were installed in an 'ad hoc fashion” without consideration to acoustic engineering or a proper investigation into where they would be most beneficial.

There has always been a debate around the efficiency of sirens to warn people about tsunami, he says.

'The Ministry has always maintained that if you choose to use sirens, because of their limited value, they should only been used if you have voice over capability.

'But those systems are hugely expensive. I saw 18 sirens were recommended for Tauranga city and that's going to be around the $1 million mark to install.”

Ideally, multiple systems should be used to warn people of an approaching tsunami which would include sirens but also text message alerts, plus information transmitted via radio and television.

Each system had their benefits and flaws and there was no 'one single silver bullet”.

'The important thing is if you live in coastal areas you need to be familiar and respond to the natural signs – that's the key message

'The other key message we want to get out there is for people to have an evacuation plan in case of a tsunami.

'In the event of an earthquake the sirens may not operate anyway, they may have been knocked over, so do not rely on the sirens alone.”

For more information on what to do in the event of a tsunami visit www.getthru.govt.nz/disasters/tsunami/