1D ultrasonic transducer unit for hazard identification for a vehicle, comprising a housing, at least three ultrasonic transducers and a control unit, wherein - the control unit is designed for the purpose of individually activating each ultrasonic transducer, - each ultrasonic transducer comprises a respective transducer housing, a respective piezoelectric body arranged in the transducer housing and a respective sound coupling-out layer, which is arranged at an open end of the transducer housing, for decoupling in a gaseous medium and is arranged at a fixed position in the housing - each ultrasonic transducer is designed for the purpose of radiating and/or receiving a sound wave with a matching work frequency, - the work frequency of the sound waves lies in a range of 20 kHz to 400 kHz, - each two directly adjacent ultrasonic transducers in the housing have a spacing from centre of sound decoupling layer to centre of sound decoupling layer of at most 10 cm or at most 5 cm or at most 2 cm, - the 1D ultrasonic transducer unit has one sound channel per ultrasonic transducer, - each sound channel has an entry opening and an exit opening, - exactly one of the entry openings is associated with each sound decoupling layer, - the exit openings are arranged along a straight line, - the exit openings are each arranged in a first wall of the housing or the sound channels penetrate a wall, which does not bear against the vehicle, of the housing, - a spacing from the centre of one of the exit openings to the centre of a directly adjacent exit opening at most corresponds with the wavelength in the gaseous medium or at most half the wavelength in the gaseous medium, - wherein the spacing between two directly adjacent exit openings is smaller each time than the spacing of the ultrasonic transducers associated with the corresponding entry openings, - a quotient of an area of the exit opening to an area of the entry opening has a value between 0.30 and 1.2 and - each sound channel has at least a length corresponding with the diameter of the entry opening, characterised in that - the housing is mountable on the vehicle, - the housing has a movable cover device, wherein the cover device is designed for the purpose of closing the exit openings of all sound channels, - the exit openings of all sound channels lie in a curved area. - the control unit is designed for the purpose of individually activating each ultrasonic transducer, - each ultrasonic transducer comprises a respective transducer housing, a respective piezoelectric body arranged in the transducer housing and a respective sound coupling-out layer, which is arranged at an open end of the transducer housing, for decoupling in a gaseous medium and is arranged at a fixed position in the housing - each ultrasonic transducer is designed for the purpose of radiating and/or receiving a sound wave with a matching work frequency, - the work frequency of the sound waves lies in a range of 20 kHz to 400 kHz, - each two directly adjacent ultrasonic transducers in the housing have a spacing from centre of sound decoupling layer to centre of sound decoupling layer of at most 10 cm or at most 5 cm or at most 2 cm, - the 1D ultrasonic transducer unit has one sound channel per ultrasonic transducer, - each sound channel has an entry opening and an exit opening, - exactly one of the entry openings is associated with each sound decoupling layer, - the exit openings are arranged along a straight line, - the exit openings are each arranged in a first wall of the housing or the sound channels penetrate a wall, which does not bear against the vehicle, of the housing, - a spacing from the centre of one of the exit openings to the centre of a directly adjacent exit opening at most corresponds with the wavelength in the gaseous medium or at most half the wavelength in the gaseous medium, - wherein the spacing between two directly adjacent exit openings is smaller each time than the spacing of the ultrasonic transducers associated with the corresponding entry openings, - a quotient of an area of the exit opening to an area of the entry opening has a value between 0.30 and 1.2 and - each sound channel has at least a length corresponding with the diameter of the entry opening, - the housing is mountable on the vehicle, - the housing has a movable cover device, wherein the cover device is designed for the purpose of closing the exit openings of all sound channels, - the exit openings of all sound channels lie in a curved area.