This app works in conjunction with a separately purchased USB ultrasonic microphone to record and analyze ultrasonic bat echolocation calls (and thus can be used as a bat detector), as well as other high frequency bioacoustic signals from cetaceans, insects, and other animals. It can also be used to record audible signals such as bird songs using a non-ultrasonic USB microphone.
The app supports many USB microphones (ultrasonic or not) that conform to the USB audio class specification, such as any Dodotronic Ultramic USB microphone or Hydromic USB preamplifier, the Pettersson Elektronik M500-384 ultrasonic microphone (note that the M500-384 is a different model than the Pettersson Elektronik M500), Avisoft's UltraSoundGate 116Unb ultrasonic microphone, or the non ultrasonic Samson GoMic USB microphone. The app also supports Binary Acoustic Technology's miniMIC line of ultrasonic microphones. By default, the app will use the highest sampling rate supported by the USB microphone - however, the app's Settings allows for specifying other sampling rates if the USB microphone supports this feature. Note also that the app records in 16-bit mono only.
The app can also be used to record audio from the Android device microphone or from frequency division, time expansion, or heterodyne bat detectors using an audio cable plugged into the TRRS jack. However, please note that in these cases, the incoming signal is not ultrasonic.
This app displays a real-time spectrogram (on a linear or logarithmic frequency scale) and the wave amplitude for both incoming signals, as well as for previously made recordings (saved as uncompressed, geotagged WAV files). The display can be zoomed, and the visualization can be enhanced using a variety of configurable color palettes. The app also can display a power spectrum for any point in a recording. Finally, in order to facilitate quick field measurements, the app has a 'caliper' tool, which attempts to place a frequency and time axis overlay on top of any sound feature that a user double taps on.
This app supports the ability to audibly monitor ultrasonic sounds simultaneously while recording, using real-time frequency division, heterodyne tuning (manual and automatic), or frequency low pass filtering of the incoming signal. Recorded ultrasonic signals can additionally be played back in the audible range using time expansion. Time expanded versions of recordings can also be exported.
This app also can be set up for recordings to be triggered automatically based on frequency and intensity. In addition, listening periods can be set up using a timer, and the app can send SMS messages and/or emails whenever a recording is automatically triggered.
The app can store metadata (location, recording device model, time stamp) inside recorded WAV files using either the XMP or GUANO metadata format. The app can also save recordings directly to a writable SD card if your Android device supports it, as well as export GPS Exchange File formatted tracks, useful for transects.
Please note that the USB microphones require an Android device that supports USB OTG for power. In addition, you must use a USB OTG cable (a standard USB cable will not allow a USB microphone to be powered). This is not a requirement for non-ultrasonic microphones plugged into the TRRS jack.
IMPORTANT note to Android 6.0+ users: The location permission and SMS permission are optional - the location permission is only needed to geotag recordings, and the SMS permission is only used to send text messages when a triggered event occurs. All other permissions must be granted for the app to run - otherwise you will get a permissions error message.
A PDF version of the Bat Recorder user manual in several different languages can be found at http://manuals.batrecorder.com.