[Harry Robins]

Just as I was finishing a carpet, I noticed that one of the vacuums was making a slightly different sound to the other.  Nothing too dramatic, just slightly higher pitched (especially during the first few seconds of starting).  I checked both for suction, there didn't seem to be any difference between them.  I'm using a Steempro Powerplus.
Do you think I have much to be worried about?  Thanks.

[Kinver_Clean]

It may be the brushes near the end of their life- I would check them out.
Also it may be a vac stack pipe a bit blocked with debris, maybe a fluff filter has a hole.
A new set of brushes are not hard to fit and are a lot cheaper than a new motor.

[Harry Robins]

Thanks Kc for feedback, Will check it out tomorrow.
Had another look today (before reading your reply); noise was still there, I also noticed a hint of a burning smell.  Do you think this could still be brushes or vac stack? 

[Kinver_Clean]

Burning smell point at brushes.

[Harry Robins]

Cheers.