Living close to LHR and being an 'enthusiast' one soon got to know the distinctive noise of the Trident 3 , quite an achivements Tridents were pretty noisy anyway. Looking at the pics in the posts the engines look tiny compared to modern-day turbofans and I am not sure the Spey could really be called a turbofan as there is no separate exit for fan-generated thrust as was the case on the first fan jet 707s .
While on the subject I always wondered how a Caravelle would perform with only one engine since being an early generation jet it must have had a pretty heavy airframe and a hefty four wheel main gear