The BatLib App plays the different ultrasonic calls of the most common european bat species transformed into the audible space with the heterodyne mixer method. This is is especially useful to compare with the live output produced with the BATSCANNER device for species identification. 1. Enter the frequency displayed by your BATSCANNER to filter species 2. Listen to the typical bat call sequences 3. Compare the sound to what you hear from your BATSCANNER 4. Sounds similar? Display additional i