Cant say for the 1, but way back when I had my kettle if I ran the expansion system on it I had same problem, my solution was
twin air horns one mounted either side of radiator with home made brackets they were fitted to rear of rad to keep out of road muck way, and also from the front you could not see them.........downside, have to find an area for compressor, need to keep relay fairly dry and make brackets. Was it worth it you bet when horn pushed sound would have made a ghost jump.

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Over winter I am making a system using a 900rr nos harpoon inox can, if that is loud I will do the above to mine.