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Started by David Brinicombe
Default_user
about 4 years ago

I found your site through BBC R4 and it sounded interesting, but I soon found problems. The first display which came up was of three Pipistrelle species, one of which I marked and clicked on. The display then changed and I was unable to mark the other two species but see below.

Problem 1 There is no back button

Problem 2 to quote:

Step 3 Consult the field guide to identify the sound.

For a start, these items need a live link to take you to the field guide. The "field guide" I eventually found didn't have proper species information or a means of reporting the species found.

Clicking on, I found an interesting call, marked it and then lost it without being able to comment. It was a bat call in a confined space with many close echoes. Without a horizontal time line, it is impossible to measure the distance of these echoes. (D = 1/2 X 340mm per millisecond)

Another clue which I use frequently in my own bat recordings is the doppler shift as they fly which is most obvious with Horseshoe species. I have two roosts with Rh and Pa bats and neither of these seems to be represented in your pages.

I have managed to get back to the starting display with the three bats. The frequency scale is muddly as it is scaled in 8KHz steps - please fix - but I see three species, soprano pip, common pip and probably an indistinct Serotine making an accelerating call. This is not a feeding buzz but the acceleration as due to approaching an obstacle which is not in your guidelines. Taking this one display, how do I report my findings?

Another display, which I have now lost, had a persistent insect sound like a cricket, too consistent to be a bat call but with a limited sweep frequency range which could confuse some people. I think this should be added to the samples of types of sound.

I've seen nothing so far on identifying Myotis species except for the Md call. These are the tricky ones and the frequency range can vary due to the absorption of high frequencies by the air. This is poorly understood but can be crucial when using bat detectors. Very crudely, you lose frequencies above 50KHz after 30 metres. The extreme example is Rh at about 109 KHz which can't be detected over 6 metres according to the Eurobat document. Many experienced bat researchers remain unaware of this limitation. Another related misconception is that only Noctules fly up to 100 metres high, but in fact Noctules are the only species we can detect 100 metres high.

David Brinicombe

Default_user
about 4 years ago

Correction: The second Pip is more likely a Nathusius

Default_user
about 4 years ago

Hello David!

I've pinged a member of the science team so hopefully you'll get a comment from them, but in the mean time I'll offer my knowledge of the project.

The focus of this project is not the species identification of the bats in the recordings, but of detecting the calls in the first place, with one of the end goals being building an automatic detection system that can be used on larger datasets.

Regarding your problems with the interface, I am not sure how you are losing clips. To quickly run through the process: Mark out a selection box, choose the type of sound, and save selection. Repeat as necessary for additional notable sounds in the clip. Once you're done, hit 'Next Sound.' You can then favorite(save for your own purposes, accessible via your profile) the recording if you wish, and choose to discuss it here on talk. After you choose yes or no to discussing the recording, you're presented with a new recording.

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