What is the emergency aid exception to a warrant to enter a home without a search warrant?

The " 'police may enter a home without a warrant when they have an objectively reasonable basis for believing that an occupant is seriously injured or imminently threatened with such injury.' [Citation.] ' "The need to protect or preserve life or avoid serious injury is justification for what would be otherwise illegal absent an exigency or emergency." ' [Citation.] ' " '. . . [] The ' "emergency aid exception" ' to the warrant requirement 'does not depend on the officers' subjective intent or the seriousness of any crime they are investigating when the emergency arises.' [Citation.] Rather, the exception 'requires only "an objectively reasonable basis for believing . . ." [citation] that "a person within [the house] is in need of immediate aid." ' [Citation.]" (People v. Troyer (2011) 51 Cal.4th 599, 605.)