1. WUTS weak unknown train sources

2. WUTS weak unknown train sources
These weak trains were first spotted in data from rias in the SW of England.
They were then seen in data from mangrove swamps in Australia, in the Gulf of California, the Gulf of Maine, the Gulf of Alaska, the Baltic Sea and other places.
In most locations they are rare.

3. WUTS v NBHF trains
WUTS
NBHF train
1. AMPLITUDE
always < 100, often <50
any
2. amplitude envelope
usually nearly flat
usually rounded
3. amplitude trend reversals
many
few
4. MULTIPATH
very little or none
often present
5. CONTEXT 2 minutes before and after
usually no other WUTS
usually train fragments or trains
6. CLICK RATE
often very high, rarely < 40/s
usually < 100/s
7. click rate modulation
very smooth sweeps, usually monotonic
less smooth sweeps, with multiple trend changes
8. FREQUENCY
maybe centred around 80kHz and 120kHz
centred around 130kHz, range kHz
9. BANDWIDTH
few clicks have minimum bandwidth
many clicks have minimum bandwidth
10. CLICK DURATION
usually < 7 cycles
often > 7 cycles
Problem: none of these criteria are strongly discriminatory!
In the Gulf of Alaska the KERNO classifier is inadequate because of the WUTS.
The F-POD should help - more detailed features, and full waveform capture.

4. A very difficult one:

5. Modal frequencies vary, with possibly some clusters around 160, 124, and 80kHz.
Do these indicated different species?
Smooth click rate sweeps are typical and were the first feature to reveal WUTS.
These sweeps can start as high as 7000 clicks/s and are then only seen in the CP1 file as the train detection does not go that high.

9. These show unusually complex patterns of click rate modulation:

10. At present WUTS have only been identified in POD data.
They must exist in the data from studies collecting .wav files, but evade all detection algorithms because they are weak …
except for train detection. They are commonly seen as high quality trains.
Please send any examples or queries to
the end