Ear speaker (mobile phone) usage with Arduino

I would add voice ability in one of my project adding these miniature button like ear speakers widely used in mobile phones. For instance:


Usage would be in "loud speaker mode", i.e. to be hear clearly 1m away from person. Circuit should be the simples possible, but in the mean time preserve minimum precaution measures for arduino output pin. I would use PWM .

Unfortunately, I'm unable to find any relevant datasheet about these speakers in order to design minimum necessary circuit to satisfy desired specs. I do not believe it is necessary any more complex circuit than simple low pass filter and maybe one transistor.

Anyone had experience with?