Implementations of the present disclosure are directed to an injection device (102) including a medicament reservoir (103) configured to store a medicament to be expelled by the injection device (102), an acoustic source (122a, 122b, 122c, 122d, 200, 300, 400) configured to generate an acoustic signal including information indicative of an amount of the medicament stored in the medicament reservoir (103), the acoustic signal being transmitted to an external device (104) configured to process the acoustic signal and to extract injection device data.