Table 2.
Acoustic characterization of MFAS packets detected at West and East HARP locations from 2011 to 2014 (no MFAS was detected in 2010). MFAS packets include groups of frequency-upsweep, downsweep and tonal pulses that occur within 5 s of each other. Encounter durations are shown in hours and minutes (HH.MM), with mean (top) and range (bottom) shown for years with multiple encounters. The inter-packet interval is the time between the end of one sonar packet and the beginning of the next, omitting breaks (gaps greater than 10 min). Received level (RL) is reported as peak-to-peak (PP) and root-mean-square (RMS) values. Sound exposure level (SEL) is the cumulative sum-of-square pressures over the duration of a sonar packet. For each metric, mean ± s.d. are shown in bold and 10th, 50th, 90th percentiles are shown in parentheses. Note that the number of described packets does not equal total packets due to duty cycled data and peak-to-peak received level threshold (115 dB re: 1 µPa).
| 2011 |
2012 |
2013 | 2014 | |||
|---|---|---|---|---|---|---|
| West | East | West | East | West | East | |
| dates with MFAS | 21 Aug | 21 Aug | 28 Aug–1 Sep 21 Sep |
27 Aug–9 Sep 21 Sep |
16 Dec | 16 Jan 8–17, 21–22, 24–28 Sep |
| number of packets encounter duration (HH.MM) |
215 | 89 | 257 | 949 | 51 | 668 |
| 08.18 | 03.41 | 01.06 | 2.05 | 01.05 |
8.50
(00.43–18.50) |
|
| (00.06–04.47) | (00.01–14.42) | |||||
| packet duration (s) | 2.0 ± 0.5 | 2.1 ± 0.5 | 2.4 ± 0.4 | 2.0 ± 0.4 | 2.4 ± 0.5 | 6.0 ± 2.8 |
| (1.4 2.0 2.6) | (1.2 2.3 2.7) | (1.8 2.5 2.7) | (1.5 2.0 2.6) | (1.8 2.7 2.8) | (1.7 7.2 8.9) | |
| packet interval (s) | 40.2 ± 140.4 | 58.4 ± 181.4 | 106.9 ± 63.7 | 92.2 ± 57.2 | 49.3 ± 33.7 | 69.4 ± 59.4 |
| (6.7 15.0 41.4) | (7.5 22.1 51.5) | (12.4 97.7 193.8) | (30.1 96.5 192.1) | (39.2 40.1 57.4) | (12.2 49.9 192.8) | |
| RL PP (dB re: 1 µPa) | 136.3 ± 9.9 | 123.7 ± 4.8 | 119.9 ± 4.3 | 120.3 ± 4.7 | 120.8 ± 4.8 | 123.0 ± 6.4 |
| (123.7 135.4 149.6) | (117.4 123.5 129.4) | (115.4 118.6 125.9) | (115.5 118.8 127.6) | (115.6 120.4 127.0) | (116.4 121.2 133.0) | |
| RL RMS (dB re: 1 µPa) | 118.0 ± 10.6 | 104.3 ± 5.9 | 98.8 ± 3.5 | 102.2 ± 5.5 | 100.7 ± 4.7 | 101.9 ± 6.3 |
| (104.4 116.5 132.2) | (97.2 103.4 112.1) | (95.8 98.0 102.5) | (96.4 101.1 110.3) | (96.4 99.2 105.7) | (96.4 99.9 111.6) | |
| SEL (dB re: 1 µPa2-s) | 120.9 ± 9.9 | 107.4 ± 5.1 | 102.5 ± 2.9 | 105.1 ± 5.0 | 104.4 ± 3.8 | 108.9 ± 5.1 |
| (108.1 119.3 134.7) | (101.5 106.3 113.4) | (99.8 101.9 105.8) | (99.9 103.7 112.8) | (100.7 103.5 108.4) | (103.4 107.8 116.1) | |