A method for customized monitoring of sounds caused by respiratory distress in a group of farm animals in a specific farm, stable, or section of a stable, comprising the following steps: a) recording the noises generated in the group of the farm animals over a certain period of time; b) converting the analogue recording into digital data; c) performing filtering operations, which filter off background noises from sounds caused by respiratory distress; d) counting the number of sounds caused by respiratory distress during the recording time; e) calculating the respiratory distress index being the number of sounds caused by respiratory distress within a pre-defined period of time, optionally corrected for the number of farm animals within the reach of each microphone; f) monitoring and storing the RDI over a period of time and calculating a time-dependent individual relevant threshold for the RDI of the specific farm, stable or section of a stable based on the stored RDI data of the specific farm, stable or section of stable; g) reporting the resulting RDI data, in relation to the threshold calculated in step f) and providing an early warning of respiratory distress based on a comparison of the calculated RDI data and the time-dependent individual relevant threshold, wherein the steps c) to g) are carried out by a processor, wherein the calculation of the time-dependent individual relevant threshold for the RDI in step f) is carried out by statistical process control; characterized in that a factor F is calculated by dividing the difference between the latest aggregated RDI_AGG value and the previous RDI_AGG value by the standard deviation of the series of historical RDI_AGG data (23, 24), wherein RDI AGG values (8.2) are RDI-values aggregated over longer time intervals; and this factor F is used to define the early warning. a) recording the noises generated in the group of the farm animals over a certain period of time; b) converting the analogue recording into digital data; c) performing filtering operations, which filter off background noises from sounds caused by respiratory distress; d) counting the number of sounds caused by respiratory distress during the recording time; e) calculating the respiratory distress index being the number of sounds caused by respiratory distress within a pre-defined period of time, optionally corrected for the number of farm animals within the reach of each microphone; f) monitoring and storing the RDI over a period of time and calculating a time-dependent individual relevant threshold for the RDI of the specific farm, stable or section of a stable based on the stored RDI data of the specific farm, stable or section of stable; g) reporting the resulting RDI data, in relation to the threshold calculated in step f) and providing an early warning of respiratory distress based on a comparison of the calculated RDI data and the time-dependent individual relevant threshold, wherein the steps c) to g) are carried out by a processor, wherein the calculation of the time-dependent individual relevant threshold for the RDI in step f) is carried out by statistical process control; characterized in that a factor F is calculated by dividing the difference between the latest aggregated RDI_AGG value and the previous RDI_AGG value by the standard deviation of the series of historical RDI_AGG data (23, 24), wherein RDI AGG values (8.2) are RDI-values aggregated over longer time intervals; and this factor F is used to define the early warning.