What on earth is that noise: Parliament's bell keepers.

Behind many MP interviews is an incessant ringing. It's like parliament itself has tinnitus, or is trying to drown out its inhabitants. What is that noise?

If you watch television news, you've probably seen a fair share of interviews with MPs from 'the tiles' of Parliament.

You know the drill - members scurry, parade, or swagger over the bridge into Parliament, and are met by a melee of cameras and microphones, belonging to a jamboree of interrogative journos.

A MP submerged under a media scrum on parliament's 'tiles'.

The "explain what you meant by / do you stand by what you said..." questions are recited and the answers end up as soundbytes on the news.

In the background of all of those soundbytes, you will have noticed a constant ringing sound - it's pretty hard to ignore. Like so many things at Parliament, there is method in the madness - which in this case manifests as the routine ringing of a bell that sounds a bit like an ailing fire alarm.

The bells, officially known as the division bells, ring out across the precinct shortly before 2pm on sitting days. Traditionally, they were used to summon MPs to the chamber to conduct a vote - or division. They still ring for that purpose on conscience issues, but these days, they operate more generally to tell MPs "hey, get down to the chamber, the sitting is commencing."

They don't just ring out in members offices though, oh no. The division bells are played electronically in every corner of the parliamentary precinct. That includes the Beehive, Parliament House, the Library, the Parliamentary Service offices 500 metres down the road, and yes, even in the toilets around parliament.

Maintenance of the bells is one of the many responsibilities of parliament's audio visual services team. Every so often, the team audits the roughly 400 bells around the buildings to ensure they're all still loud enough.

You'd hope an MP would know when they need to be in the chamber, but the bells are a sort of insurance in case they forget. Interestingly, the bells failing to ring in any part of the precinct is not an excuse for invalidating a vote.

A few weeks ago, on a chilly Sunday morning at 6am, The House tagged along with Cameron and Sam from AV services as they embarked on a bell-quest, seeking out bells from the rafters to sub-basements across the precinct. You can listen to audio from that at the top of this page.

RNZ's The House - journalism focussed on parliamentary legislation, issues and insights - is made with funding from Parliament's Office of the Clerk.

Go to this episode on rnz.co.nz for more details