Until now the intelligent, controlled and automated use of acoustic bio-responses in cattle-houses as indicators of animal-condition was limited to human perception. The appearance of coughing, sneezing, etc may point to an environmental deficiency in the animal habitat or the presence of diseases among the cattle. In order to use this kind of acoustic information as a bio-response signal in practice, it is necessary to develop a simple on-line measurement algorithm. In this paper an on-line registration technique for pig coughing is presented. The application of a distance function to a spectral sound analysis allows to distinguish coughing (94%) from other animal and environmental sounds like metal clanging (72%), grunting (99%), noise (93%), etc. The sound database (10 data sets) was collected on a group of 6 healthy animals. Each of the test-animals was repeatedly placed in a laboratory installation in which coughing was induced by evaporation of citric acid.