I am designing a board which communicate wirelessly with a smart phone. When I send a specific command, I want it to sound an alarm to the user, making it able to be found when lost. My board runs on a coin cell 3V battery, which has a current drain which should not go above 15mA. The sound unit should not exceed 10mm in diameter. I struggle to find any speakers or buzzers which can operate within these conditions, so my question is:
What methods and/or components can be used with 3V, max 15mA circuit to notify a user using an audio signal around 70dB SPL?