Assuming you’ve already configured Audacity in “nocmog mode”, when you first open a long recording it will looks something like this. The recording is just over 2 hours long and is in stereo, hence two spectrograms, for the left and right channels.
You need to zoom in to see the calls. This can be done by repeatedly clicking the magnifying glass icon (), but this is slow. I find it easier to use the mouse to select a short section at the start and click the zoom to selection button (). Having zoomed in a bit, now select 20–30 seconds and press this again – now you have 20–30 seconds fitted to the screen which is adequate for scanning for calls (but see here).
The “ruler” along the top now shows values from 0 to 30 but it would be helpful if these were real times to assist extracting precise flight times, or for processing hourly blocks for Trektellen. A trick for this is to ensure your cursor is at the start of the recording (click in spectrogram then press keyboard Home key) use the menu option Generate > Silence, to add a period of silence corresponding to the start time of the recording. This recording started at 22:16:13, so I add 10 hours, 16 mins and 13 seconds of silence:
Now my recording has real times along the top, I can scroll past the added sound to the start of the recording proper and I am ready to scroll through looking for bird calls. These steps are shown in the following video, in which two Redwing calls are evident, a faint one at 10:16:47 and a clearer (closer) one at 10:21:00.
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