Heard, 29, was overwhelmed with the gesture and started crying holding a girl's hand, who was given the aid by Depp, reported Us magazine.
"There's nothing quite like the feeling of seeing that moment where you're testing the hearing aid and testing it... And that moment where they light up as they hear. That moment is everything," Heard said.
The 52-year-old "Black Mass" actor's all-star band, The Hollywood Vampires, which also features Alice Cooper and Aerosmith's Joe Perry, announced their involvement with Starkey Hearing Foundation in August.