Nielsen has confirmed that it has bought audience data business VisualDNA for an undisclosed sum, The Drum can reveal.The acquisition comes just a day after it was reported that Nielsen had paid $560m for media metadata business Gracenote. VisualDNA is an audience data business that supplies data to brands, agencies and publishers. The data is based off the results of a psychographic personality test that's been taken by over 40m people.A spokesperson for Nielsen, said: "I can confirm that Nielsen has completed an acquisition of VisualDNA, a leading audience personality data provider and marketing technology company."He said the business wouldn't comment on the price of the deal but that it was made to bolster the Nielsen Marketing Cloud rollout:"For Nielsen, the acquisition brings together the UK's two leading data players into a powerful new union. Additionally, the VisualDNA analytics solution, consumer survey capabilities and data footprint will enhance Nielsen Marketing Cloud rollout in Europe," he added.Additional reporting by Charlotte McEleny, Asia editor.