Patent Document ID: 9031791
Application ID: 12972334
Patent Flag: 1

Claim One:
1. 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 a plurality of different types of events comprising rock fall events, train events wherein a train travels over the track section and highrail vehicle events wherein a highrail vehicle travels over the track section and wherein the signal processing unit is configured to discriminate rock fall events from train events or highrail vehicle events; 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; wherein the signal processing unit is configured to detect a start of the event and an associated time t start , for the particular one of the ballast sensors, when a STA/LTA parameter associated with the corresponding ballast sensor signal is greater than a start trigger threshold (thresh_start); wherein the signal processing unit is configured to determine the STA/LTA parameter for the corresponding ballast sensor signal according to one of: ( 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 ⁢ ⁢ and ⁢ ⁢ n ≥ a , b ( i ) where: x i represents a value of an i th sample of the corresponding ballast sensor signal, n is an index of a current sample x n , a is an STA duration constant, b is an LTA duration constant and ( STA LTA ) n is the STA/LTA parameter; and ( STA LTA ) mod , n = ∑ i = ( n - ( a - 1 ) ) i = n ⁢ ⁢ x i a c ⁢ ⁢ where ⁢ ⁢ n > a > 0 ( ii ) where: x i represents a value of an i th sample of the corresponding ballast sensor signal, n is an index of a current sample x n , a is an STA duration constant, c is an experimentally determined constant that is representative of an LTA during event free times and ( STA LTA ) mod , n is the STA/LTA parameter.