What is the test for a police officer to invoke the emergency aid exception?

protect an occupant from imminent injury. [Citations.]" (Brigham City v. Stuart (2006) 547 U.S. 398, 403-404.) "This 'emergency aid exception' does not depend on the officers' subjective intent or the seriousness of any crime they are investigating when the emergency arises. [Citation.] It requires only 'an objectively reasonable basis for believing,' [citation], that 'a person within [the house] is in need of immediate aid,' [citation]." (Michigan v. Fisher (2009) 558 U.S. 45, 47.) "Officers do not need ironclad proof of 'a likely serious, life-threatening' injury to invoke the emergency aid exception." (Id. at p. 49.)