For emergency call takers who worked on the day of the Christchurch earthquake in 2011, it's the sound and the voices of the day they remember most.
From inside the communications centre, they couldn't see the destruction outside, but they could hear it.
Now, some of the audio from Fire and Emergency's response to the disaster is being played for the first time.
From the moment the quake hit, calls over the radio didn't stop.
"We're just having a large earthquake now, over."
"Looks like she's been a good one in town here."
"Town is chaotic."
FENZ crews from across Canterbury then sprung into action.
"Priority message, persons reported building collapse at Gloucester St."
"Building collapsed, multiple trapped and casualties."
"Possibly 70 people trapped in a multi-storey building collapse."
Lyn Crosson, shift manager of the FENZ southern communication centre, says the calls kept coming in.
"The calls started coming in, and then you realised that this was a totally different kettle of fish," she says.
The severity then started increasing.
"We have a fatality out here."
"Multiple building collapses, multiple persons trapped."
"We've got a floor collapse with 11 people missing."
Crosson and her team did whatever they could to help.
"When you get a call about a house fire, you can tell people 'get out of the house' and all that. You can't say that an earthquake's not going to happen or stop," she says.
Sometimes, being a calm voice on the end of the phone was all they could do.
"Getting calls from people who were getting texts from friends and family saying 'I'm stuck in such and such a building', and then not being able to get a hold of them."
When Crosson's 12-hour shift finished, she got to see the damaged city for herself. She had hoped things weren't as bad as they had sounded.
"You're having to tell yourself it's real, it's not a movie scene. You have cars crushed, you have collapsed buildings, and curtains blowing out of broken windows," she says.
Ten years on and these recordings from February 22 are a raw reminder of the earthquake's destruction.
"Three people missing, one confirmed K41-1," the audio says, which is the code to say someone is dead.
For those who needed help on that day, there's another sound they will remember too, the calm voices of emergency call takers during a moment of tragedy.