The invention concerns an acoustic alarm safety device comprising a case (2), a vibrating element (20) associated to a membrane (22) so as to make it vibrate, electrical means for providing a control signal to said vibrating element, and means (18) for actuating the electrical means. This device is characterized in that it further comprises a pierced backcover (28) attached to said case (2) and arranged so as to protect it, and so as to allow a vibration of the set of the vibrating element-membrane (20, 22), said backcover being attached to said case in a manually removable manner, and a fitted ring (26) to which is attached said membrane (22), said ring (26) and said membrane (22) being associated to the case in such a way that the set ring-membrane (26, 22) ensures the waterproofness of the case (2).