I'm intrigued by the idea of how noisy Colossus was, it was largely electronic.
The high bits of the counters were all relay logic, to keep the valve count down (they didn't need to switch as quickly). And there were a few multiselectors and things in there too. And of course the paper tape reader isn't exactly quiet when up to speed. What you hear depends on the (hard-wired!) program it's running, but if you imagine the paper tape spinnning at 5000CPS, a clatter of relays every time it complete a full loop, and the occasional burst of printer noise, you're on to the right idea.
I've no idea what the original power supply arrangement was. The rebuild project uses a modern telecoms PSU, but if there were rotary converters involved, you'd have to allow for that, too (though they might have been housed elsewhere).
The Bombes that Turing used to decode Enigma were electro-mechanical, so would have sounded like telephone exchanges.
Less so than Colossus, I expect. They were mostly rotating multi-pole switches linked with belts and gears, rather than relays. I've not seen the Bombe rebuild in action, though.
As I mentioned earlier, there's a lot of telephone exchange in Collosus, but it doesn't have the instantly recognisable telephonic rhythms.
