Trumpets under the hood

[brucemillar]

Folks

My (New to me) 4.8is makes a sound (I think from the windscreen scuttle area) like a trumpet when I get up to 65mph. This stops if I go above 70mph or drop back below 65mph.

I am sure it is wind noise? But cannot find what is causing it.

I have tried (when it is making the sound):

Switching on the windscreen wipers = No effect.
Folding in the mirrors = No effect.
Putting Gaffa Tape over the letterbox slot for the pollen filter so there are no air gaps = No effect.

It does sound like it comes from the scuttle area under the windscreen where the pollen filter slots in.

I removed the scuttle, cleaned all the debris out and fitted new screw studs and a new pollen filter. No effect.

This is a loud noise and spoils a nice run out. When it starts it is monotone but just fades out as you drive thru it. It also fades in as you drive up to it.

Anybody had this? Anybody know how to stop it?