A system for detection of rock fall in a vicinity of a section of railway track, the system comprising: a plurality of ballast sensors spaced apart along the track section, each ballast sensor located in a ballast proximate to the track section but spaced apart from rails and ties associated with the track section and each ballast sensor sensitive to acoustic energy and configured to generate a corresponding ballast sensor signal in response to detecting acoustic energy; a signal processing unit operatively connected to receive the ballast sensor signals from the plurality of ballast sensors, the signal processing unit configured to detect rock fall events in a vicinity of the track section based, at least in part, on the ballast sensor signals; wherein the signal processing unit is configured to detect an event for a particular one of the ballast sensors based, at least in part, on its corresponding ballast sensor signal; and wherein the signal processing unit is configured to detect a start of the event, for the particular one of the ballast sensors, when a STA/LTA parameter, i.e. a ratio of a short term average to a long term average parameter, associated with the corresponding ballast sensor signal or an approximation of the STA/LTA parameter associated with the corresponding ballast sensor signal is greater than a start trigger threshold, thresh_start, the STA/LTA parameter given by: STA LTA n = ∑ i = n − a − 1 i = n x i a ∑ i = n − b − 1 i = n x i b where b>a>0; n ≥ a, b; x i represents a value of the i th sample; n is an index of the current sample x n; a is a short term average duration; and b is a long term average duration. a plurality of ballast sensors spaced apart along the track section, each ballast sensor located in a ballast proximate to the track section but spaced apart from rails and ties associated with the track section and each ballast sensor sensitive to acoustic energy and configured to generate a corresponding ballast sensor signal in response to detecting acoustic energy; a signal processing unit operatively connected to receive the ballast sensor signals from the plurality of ballast sensors, the signal processing unit configured to detect rock fall events in a vicinity of the track section based, at least in part, on the ballast sensor signals; wherein the signal processing unit is configured to detect an event for a particular one of the ballast sensors based, at least in part, on its corresponding ballast sensor signal; and wherein the signal processing unit is configured to detect a start of the event, for the particular one of the ballast sensors, when a STA/LTA parameter, i.e. a ratio of a short term average to a long term average parameter, associated with the corresponding ballast sensor signal or an approximation of the STA/LTA parameter associated with the corresponding ballast sensor signal is greater than a start trigger threshold, thresh_start, the STA/LTA parameter given by: STA LTA n = ∑ i = n − a − 1 i = n x i a ∑ i = n − b − 1 i = n x i b where b>a>0; n ≥ a, b; x i represents a value of the i th sample; n is an index of the current sample x n; a is a short term average duration; and b is a long term average duration.