Total number of echoes Jan| 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Jan| 15 16 17 18 19 20 21 22 23 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 ---+------------------------------------------------------------------------ 01 | -- -- -- -- -- -- 21 15 20 22 18 17 20 10%16 %3 8 8 6 %6 %8 IF%14%11 02 | 4 11 10 21 18%10 25 29 21 20 22 27 24 20%20 12 5 9 9 8 16 16%11 13 03 |%15 21 25 34%38 29 38 37%36%33%21 31 14 22 17 9 10 7 4 5 11 16 10 16 04 | 22 31 52 69 71 76 104 107 89 74 64%44 54 67%44%37%16%10 %7%10%13 8%11 IF 05 |%15%16%15%30%31%31%14%28%33%19%22%27%23%20 19 11 16 8 8 10 6 10 6%10 06 |%12%27%41%28%41%35%36 33 40 29 30 29 20 23 14 11 6 10 %3 5 11 -- -- -- Echoes longer than 20 seconds Jan| 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Jan| 15 16 17 18 19 20 21 22 23 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 ---+------------------------------------------------------------------------ 01 | 1 1 1 1 1 1 02 | 1 03 | 1 04 | 1 1 2 1 3 1 1 1 1 05 | 1 1 1 06 | 1