Keep the frequency range as narrow as possible
When you draw a rectangle around a call spectrogram, select the frequency range that covers that calls and also other neighboring calls, without selecting much empty space in the spectrogram.
Example: If the frequency range of a call definition is too large, there may be two consequences: first, you may include noise in the call definition. Second, the “empty” space in the rectangle above the call lowers the Min Amp parameter that UltraVox XT calculates for this definition. In both cases applying this definition results no calls being detected.
Increase the Min Amplitude parameter
If Min Amplitude is too low, UltraVox XT finds large regions of the spectrogram with low amplitude that do not match the rest of the call definition, like the Maximum duration. This happens particularly when the signal is noisy. In that case you get fewer calls than expected.
However, at some point the Min Amplitude value could be too high. Calls that were previously detected are no longer found. Adjust Min Amplitude and click Detect calls in this recording until the number of detected calls is maximized.
In the example below, a call definition was made by dragging around the first call in the spectrogram. Clicking Detect calls in this recording did not result in detection of any vocalization (top).
After increasing Min Amplitude from 111 to 200, all subsequent calls were detected.
Get a feel of the amplitude in a call
Hover the mouse pointer over the spectrogram of a call that is not detected yet. Check the values of amplitude A near the hairlines.
This way you get an idea of how the amplitude varies across the signal, and what the minimum amplitude would be required to detect similar calls.
Example: Set Min Amplitude quite a bit lower (2 to 5 times) than the values you see next to A. Click Detect calls for this recording and check whether that call is detected. Repeat this procedure when necessary to detect more calls.
In general, a short Min Duration, say around 20 ms, works well for rodents.
Keep Max duration high, unless you're specifically looking for calls shorter than a certain length.
In the following example, the second signal was not detected. The signal met the Amplitude and gap criteria, except for it was longer than the Maximum duration set to 200 ms. After increasing the Max duration, the signal was detected as a call.
Example: In the following recording, continuous noise is present around 50 KHz.
Make sure to minimize noise in your recordings; see Experimental setup.
Also check the Amplitude-time plot. If it looks like the following:
Before recording new data, adjust the microphone gain to make sure that there is a significant gap between the peaks of the signal and the margins of the plot, like here: