The CRM integration does not clean up any duplicates that originate either in Salesforce or Acoustic Campaign.
If you have a duplicate mess in your CRM, expect it to be recreated in your marketing database when synchronized. The integration is only a bridge. If you have a lot of duplicates in Salesforce, then the integration will recreate them in the Campaign. If Salesforce is loaded with duplicates, it might be a good time to clean them up before you synchronize with Campaign. Once the integration is live, it is recommended to implement duplicate prevention techniques in both applications to keep duplicates to a minimum. When duplicates occur, merge inside Salesforce. The integration will handle the merging of the corresponding Campaign records.