A method for determining the state of access control devices and sales or payment machines of an access control system by detecting sound profiles emitted during operation by a component or component group by at least one microphone. Based upon the recorded sound profile, an acoustic identification signature is created in a server or a central computer, which identification signature is based on the frequency spectrum of the recorded sound profile and/or the temporal change thereof. The acoustic identification signature is compared with a reference identification signature(s) stored in the server and assigned to a component or a component group. In the event of the detecting an acoustic identification signature which exceeds a predetermined first threshold value, increased wear of the component or the component group is detected, while if the deviation exceeds a second threshold value, a defect of the component or the component group is defected.