Push/pull numbers of identical fans in open air essentially have the same CFM/dBA curve as a lone fan. Maybe a slight improvement, but the noise is 'broader' (and technically less noticeable if the fans are good)

On a radiator, there is improvement in airflow, though whether those 4 extra fans give you better performance, no telling.

If you had counter rotating fans in open air, those are something (and on a radiator too)