"Quiet" Tyres

[jumbuck]

I have just purchased a new TDCi (new 6sp auto) and find that there is quite a bit of road noise. The reviews I have read all seem to mention this and suggest different tyres might reduce the level of noise.
Does any know or can recomend some tyres that produce less road noise? What makes them quieter - softer compound or a particular tread pattern?
Although this is my first Focus (and diesel) it is apparent that these cars handle extremely well and are a lot of fun to drive so I think they also need tyes that are up to the job.