Field sprayer nozzle pattern monitor

A field sprayer comprising a container for a liquid to be sprayed, vehicle means supporting the container for transport across the ground, a plurality of spray nozzles, a boom means carried by said vehicle means supporting said nozzles in spaced position transversely of a direction of working movement of the vehicle means, liquid supply means for communicating said liquid from said container to each of said spray nozzles each said spray nozzle having a nozzle tip arranged to generate a liquid spray pattern which projects from the nozzle tip in a spray direction, said apparatus and an apparatus for detecting faulty operation of at least one of the nozzles, the apparatus comprising a plurality of microphones, each microphone comprising a support body, a transducer mounted in said body and arranged to generate electrical signals in dependence upon air borne sound detected by the transducer, means on the body for receiving the air borne sound for communication to the transducer, means for mounting the body relative to the respective nozzle such that the receiving means of the body is positioned adjacent the spray pattern at a position downstream of the tip so as to be responsive to air borne sound emitted by the liquid spray exiting the nozzle, central detector means arranged to receive said electrical signals and to detect a deviation of any one of said electrical signals from a predetermined normal signal by a value greater than a predetermined value so as to detect a fault in the operation of the nozzle associated with said one of said signals, and display means for indicating said fault.