Nyctalus noctula Nnoc
In the open: QCF at 20 kHz or just below, steady frequency with ilterval around 0.5 s, duration above 20 ms.
Active hunting: Altering Emax between 20 and 30 kHz. Call interval around 300 ms, but very variable.
In the open the calls are of QCF-type. If they are under 20 kHz and longer than 20 ms, the identification is certain. In this case there actually is some clutter near the bat.
Sometimes it is hard to measure the call duration. The echo cloud can interfere with the original call when the bat flies not too far from vegetation. But in this case the duration is clear above 20 ms. Emac 18-19 kHz.