Where is this ruddy noise coming from!

[Brucey]

such noises can be highly elusive and can drive you completely batty in the meantime. IME 90% of the time a noise will emanate from the pedals or the chainrings so these are the first things to check. Particularly if a creak is coming from an Al-to-something joint, the noise will have been caused by tiny movements, and these will have generated black debris. IME this needs to be cleaned out; otherwise it may not matter how tight the bolts are or how much lube there is, it still might creak.

If you have a noise that can only be made whilst riding it can be very difficult to pin the source down. Noises that can be reproduced when the bicycle is stationary are much easier to deal with, eg. with a mechanic's stethoscope. Mobile/transient noises may be pinpointed using a cheap USB voice recorder; this can work because the microphone is equally sensitive to vibration as to airborne noises; the closer the recorder is sited to the source of the noise, the louder it will seem to be, all else being equal.

[Navrig]

Some chains are directional. If so, have you put it on the correct way?

[gxaustin]

I had a funny clicking noise. I even changed the BB in case that was responsible. I was still scratching my head when I just happened to notice that the cable end for the rear derailler was very close to the chain where it passed between the idlers. That seems to have been the culprit.

[sjs]

I once had an annoying once-per-pedal-revolution noise which turned out to be caused by a few coins in a jacket pocket.

[Brianjeff50]

Just an update:
Saddlebag, bar bag removed
Saddle tightened.
Shoes changed.
Pedals changed.
Cable end not flicking shoe.
No money in pocket
Chainrings removed and checked (and sent Absolute Black photo to advise on state of teeth wear - it was ok)
Reset front derailleur.
Cranks spinning free without play.
Pulled forks to check head bearings. Okay.

And after all that … it’s still feckin’ tapping!!

It’s a definite knock, not a click, creak or squeak. And it’s once every revolution - though sometimes it just stops for a short time.
I’m going to re-check the FD. It is a bit fiddly to set with oval rings. Could it be the bottom bracket, even though there’s no obvious play and it spins freely?
After that I just give up and wear ear plugs.

[rareposter]

And after all that … it’s still feckin’ tapping!!

Did you check for any stiff links in the chain?

The logical place for the issue, given that it has only started when you changed the chain, is somewhere within the drivetrain, very probably connected to the new chain you now have...

[Cyclothesist]

Just an update:
Saddlebag, bar bag removed
Saddle tightened.
Shoes changed.
Pedals changed.
Cable end not flicking shoe.
No money in pocket
Chainrings removed and checked (and sent Absolute Black photo to advise on state of teeth wear - it was ok)
Reset front derailleur.
Cranks spinning free without play.
Pulled forks to check head bearings. Okay.

And after all that … it’s still feckin’ tapping!!

It’s a definite knock, not a click, creak or squeak. And it’s once every revolution - though sometimes it just stops for a short time.
I’m going to re-check the FD. It is a bit fiddly to set with oval rings. Could it be the bottom bracket, even though there’s no obvious play and it spins freely?
After that I just give up and wear ear plugs.

Yes it could be the BB. It could also be the seatpost - try removing and regreasing it. It could be hub bearings, wheel dropouts and several other things covered in the link in my earlier post.
The thing you can't trust completely is your own unaided ears because of the way sound and vibration travels around the frame invariably appearing to come somewhere around the BB area. It's a painstaking job of elimination. Starting with common likely candidates may shorten the process.
I've been there (for me it was driveside rear hub ball bearing corrosion due to water ingress and miserly application of grease at the factory).
Let me wish you good luck!

[Brucey]

....It’s a definite knock....... Could it be the bottom bracket, even though there’s no obvious play and it spins freely?......

IME any BB can make a knocking sound if one of cups isn't quite tight enough in the frame.Re-installing the cups with loctite or epoxy resin normally stops them from moving around. In addition, IME HT2-type BBs can make noises if there is any wear between the BB spindle and the bearings.

In both instances above, the BB can rotate smoothly with no obvious play. Furthermore, the root cause should always be established and dealt with, else any respite may only be temporary.

[Brianjeff50]

And after all that … it’s still feckin’ tapping!!

Did you check for any stiff links in the chain?

The logical place for the issue, given that it has only started when you changed the chain, is somewhere within the drivetrain, very probably connected to the new chain you now have...

The chain seems okay - i cleaned and re-lubed just in case. I took a thorough look at the chainrings for any damage - ok too.

[mig]

does it make a difference to hold the 'bars more lightly?

when you say 'once per revolution' then that's the pedals? always at the same point in the 360 degrees?

[peetee]

Is your headset adjusted correctly?
Is the front mech inner plate clearing the chainrings? (This should not be assumed from the ‘correct’ height of the outer plate).
Are the gear cables fouling anywhere? (A resounding single creak comes from my partners bike when the steering is turned slightly - it’s the end of the gear outer in the frame stop!
And, as per my earlier post, can the noise be felt anywhere? (Hands, feet, bum - and this is worth trying to establish as it can be hard to notice if it is).

[drossall]

I nearly replaced my BB this year, before I noticed that the tapping noise was because my pump had moved and was getting caught by my feet

[Brianjeff50]

SILENCE IS GOLDEN! Tapping sorted at last.
On the advice of (I think) Brucey I decided to check if the bottom bracket cups were tight in the frame. I needed to get a tool for the job from my LBS so after a bit of Q&A in the shop, I thought ‘sod it, let’s invest thirty quid in a new set of bearings’. The old ones had no roughness or obvious symptoms of wear apart from some slight movement which may or may not have just been in the dust covers.
Anyway cleaned and greased it all, re-assembled and this morning all is perfect.
I would never have said there was any issue when pedalling but it’s discernibly smoother now.
So all’s well, I haven’t torn all my hair out and I’ve tackled some new to me spannerwork as a bonus.
Thanks for all the advice folks.

[Jdsk]

Well done. And thanks for posting the solution.

Jonathan