Here are the dc23 hepa filters , Old style left new style right
Brilliant, thanks for that
I'll have a look and let you know which style I've got - can believe the cost to replace though, even trade prices
Yes I have the old style HEPA filter - removed the filter, switched on and the noise disappeared
What I did do though was pull the larger rubber seal up so it sat right at the top the groove and when I refitted it like this, the whine was still gone.
I think just pulling the rubber seal out 1-2mm was enough to make it air tight again.
Will run it for a few days just to check the whine doesn't reappear but hopefully sorted without the expense of a new filter.