All pushers seem noisy to me - I've always assumed it to be the disturbed airflow form the airframe going through the prop disc.
The Cessna 337 seemed particularly noisy presumably because of the front engine's prop wash also going through the rear prop! Never heard the similarly configured Rutan Defiant, Dornier 335 or Moynet Jupiter in the air so are/were they the same?
Can remember seeing Marconi's P166 G-APWY around and about - now in the Science Museum at Wroughton and hearing (and then seeing!) a blue P180 rather more recently.