I've questioned elsewhere why the Vanguard was so noisy
Much of the noise derived from the compressors for the cabin pressurisation, driven by engines 2 & 3. IIRC On the Merchantman only eng 3 drove a compressor which theoretically should have meant less noise but I don't recall whether this occurred in practice.
Like the Trident, the Vanguard was over-complex engineering-wise. For example, the props, engine intakes and tail leading edges were anti-iced electrically, the engines internally by bleed air and the wing leading edges by hot air generated by heat exchangers taking in ambient air and warming it using exhaust gases.
Ditto the Trident: converting from the T-bird on to the 737 we were surprised to learn that, in contrast to the highly complex anti-icing system on the former's tail surfaces, the tail of the Boeing was not anti-iced at all.