The sound appears to come from the general area of the cartridge. I haven't recently replaced anything
I've already tried this.
Since you seem unaware that the Canon PBP has only one cartridge I'm not sure that you're the expert for my problem. I'm going to ask for another. Sorry.
In my second last reply to Freddie I said I'd already removed the cartridge, checked for cleanliness, and replaced the cartridge. I have also - lest there be a doubt - switched the printer off and on again.