An apparatus for checking for the presence of objects and in particular containers, comprising a transmitting device which has a sound signal generation unit for emitting a sound signal, and a receiving device which is arranged relative to the transmitting device in such a way that a sound signal emitted by the transmitting device and transmitted through air can be received by the receiving device. According to the invention, at least the transmitting device or the receiving device has a housing, wherein at least one region of this housing is suitable for emitting or for receiving sound signals.