H&K UK chief executive Marie-Louise Windeler confirmed that Noble, who was unavailable for comment as PRWeek went to press, was to depart the agency and had a six-month notice period.
Windeler said that the agency would be boosted by the planned return next week of marcoms group head Wendy Mair from maternity leave.
Freud Communications declined to return calls.
Noble joined H&K only two years ago from Dubai-based Bain Euro RSCG, where she was managing director. Prior to this, she worked at Biss Lancaster Euro RSCG.