The prototype was indeed noisy when flying in helicopter mode, but massive reductions in tip jet noise had been achieved by the time the government pulled any further funding.
Even before then, when the Rotodyne with modified tip jets visited Battersea Heliport hardly anyone knew it had been and gone. Don't forget that the airliners of the day were also VERY noisy. Even in the early '70s, the racket made by DC-8s, Boeing 707s, VC10s and Tridents was quite something!