Danny in belated response to your question re the Spey and noise in the 70s. It didn't power the noisiest subsonic aircraft at that time but it probably caused the most disruption although not with the BAC 1-11 but with the three in the Trident 1.
Whilst the 1-11 had a better climb rate than the Trident with all engines operating it was the lack of understanding of perceived decibels, minimum Noise Routings and flying procedures that caused the most disruption.
I fortunately didn't fly the original Trident 1C which was quickly re-engined because it couldn't get airborne at MTOW from Heathrow on a summer's day. The re-engined one was hardly any better, was aptly named the "Gripper" as in "Ground Gripper" and was rumoured to get airborne because of the curvature of the earth.
The NAR at LHR were avoiding the built up areas but paid no attention to the environmental noise levels.
I lived on the edge of the Slough and Maidenhead built up areas, on the Burnham/Taplow boundary..... Open spaces and just where a heavy Trident 1 would be setting climb power on a Daventry departure. The windows would shake, waves were set up in wine glasses and conversation was impossible.
It was the only aircraft that disturbed us as BEA management had a dangerous and ridiculous flying procedure.
At beginning of roll we started stop watches...and between 65 and 90 seconds we retracted trailing edge flaps and pulled back the levers to 70% thrust.
With the result that we staggered along on the back side of the drag curve spreading slightly less DBs far and wide.
At 3000ft we set climb power...around Crawfords biscuit factory on the Maidenhead road and just down the road from my semi. We then flew nearly level, at 225 knots retracted the droop and accelerated to climb speed.
If we had left the flaps at TO, set climb power, routed along the M4/A4, over Slough and it's industrial estates then less people would have been exposed to the noise nuisance and a Trident would have probably never been parked in a field at Staines!