Simply connect an inexpensive USB microphone to your iPhone or iPad (buy a microphone pre-assembled from shop.smithrobotics.co.uk or build your own from the PCBWay project at https://t.ly/BCBjN) and open your ears up to the extraordinary world of bat acoustics.
All European bats and many of the worlds "microbats" navigate, hunt and communicate using ultrasonic sounds, too high-pitched for human hearing. Bat Detector reveals those sounds to human ears, and has two different methods to make ultrasonic bat sounds audible. Firstly, it supports the "classic bat detector mode" of heterodyne bat detection. Heterodyning is a simple process that operates in true real-time, demodulating the bat sounds with a carrier signal just like an old transistor radio, but without any manual tuning. Bat Detector tunes into the strongest bat signal it can hear, and the heterodyne process turns any bats sounds it hears into percussive cracks, pops and slaps, or in the specific case of leaf-nosed bats such as Horseshoe species, strange alien warbles. The harmonic content of the sounds is distorted and mangled, so these sounds bear no relationship to the sounds the bats actually made, but rhythm is preserved, and heterodyned bat sounds are diagnostic and distinctive, so heterodyning remains an invaluable tool in the arsenal of bat workers.
Time Expansion operates in quasi real-time, capturing small snippets of bat sound and playing them back at 1/16 speed. 16 is a good number - it brings the bat sounds down to a good range for human hearing (from between 1kHz to just under 7kHz), and it preserves the harmonic relationships between the bat sounds. And as a bonus it is a musical transformation - the bat sounds are not only slowed down but are transposed down by exactly 4 octaves. This means if a bat calls a C#, you will hear a C#, but 4 octaves lower. You will be surprised how beautiful and musical bat sounds are when time-expanded. When used in conjunction with heterodyning, and with the accurate frequency read out on the display, bat species identification is made much easier and more reliable.
When "RECORD" is engaged Bat Detector will trigger a 5 second full-spectrum recording at 384kHz whenever it hears a bat, or at least something that it *thinks* sounds like a bat. These are not the recordings of the sounds you hear coming from the detector, but are the sounds going INTO the detector - the true ultrasonic sounds that the bats made, too high for humans to hear. You will need specialist software to examine these files after you export them from your device to a computer.
If you want to experience bat sounds during the daytime, in a classroom environment, or when there arent any bats around, just turn on Demo Mode in the Bat Detector section of the settings App, and Bat Detector will loop through a collection of bat recordings from Wiltshire, England.