Bat Detector2.7

Simply connect an inexpensive ultrasonic USB microphone to your iPhone or iPad and open your ears up to the extraordinary world of bat acoustics.

Build a dedicated USB microphone for under £10 : https://shorturl.at/e2A3U - : or buy one pre-assembled and tested for about £65 that also operates as a standalone bat detector https://www.apodemus.eu/nl/Apodemus-Pipistrelle-Mini/00126

All European bats and most of the world's "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.

HETERODYNE BAT DETECTION WITHOUT MANUAL TUNING

Firstly, Bat Detector supports the classic technique 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. Most heterodyne bat detectors require you to manually tune into different species, but Bat Detector operates without any manual tuning, instead it tunes into the strongest bat signal it can hear. The heterodyne process then 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. These are often thought of as "bat sounds" - they are not. They are sounds synthesised by bat detectors using bat sounds as a source - rhe harmonic content of heterodyned sounds is distorted and mangled, and these sounds bear literally no relationship to the sounds the bats actually made. However, operating in true real-time means that the rhythm of the bats calls is preserved, and heterodyned bat sounds - despite sounding nothing like bats - are diagnostic and distinctive, so heterodyning remains an invaluable tool for all bat workers and enthusiasts.

EXPERIENCE TRUE BAT SOUNDS FOR THE FIRST TIME WITH 16x TIME EXPANSION

Time Expansion was previously a very high-end, expensive option. Time Expansion in Bat Detector operates in quasi real-time, capturing small snippets of bat sound and playing them back at 1/16 speed. 16 is a number chosen for two good reasons. Firstly it brings the bat sounds down to an easy range for human hearing, the sounds generated by Bat Detector range from between 1kHz to just under 7kHz. 16x Time Expansion preserves the harmonic relationships between the bat sounds, so 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.

FULL-SPECTRUM 384kHz RECORDINGS TRIGGERED BY BAT SOUNDS

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.

DEMO MODE FOR EDUCATION AND TRAINING

If you want to experience bat sounds during the daytime, in a classroom environment, or when there aren't 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. Alternatively, if you have recordings of your own that you wish to use, create a folder called Demo in Files-> Bat Detector and Bat Detector will use these in Demo mode rather than its built-in recordings.

Version History Improved interference suppression / noise reduction, results in better reproduction of time expanded bat calls.

Switchable "Griff" filter introduces a band cut at 27kHz to match the resonant peak of Griff's FORD-2 microphone. 2.7 Apr 30 Added a 30Hz render option for older / slower devices, it should keep the device cooler. 2.6 Mar 29 More control over panning to minimize feedback when using a microphone plugged directly into your device. 2.5 Feb 3 Auto-generation of sonograms with WAVs for fast visual scanning of recordings
App can now be launched by sharing a WAV file with it, or simply clicking on a WAV file
Improved detection of quiet bats
Demo Mode now more visually apparent (green sonograms, green borders, name of demo file being replayed shown on screen) without the use of the giant on-screen badge. 2.4 10/03/2025 This version fixes an issue that arose in iOS 26 and resulted in certain UI components not being visible if the app were backgrounded and re-foregrounded.

This version has a powerful new feature, it can optionally capture a JPG sonogram file for each WAV file that it records to allow rapid visual scanning of recordings in a desktop environment, so you can very and quickly look for (for example) Horseshoe bats or unusual Myotis in amongst the crowds of Pipistrelles and Speckled Bush Crickets. The feature is turned on in Settings -> Bat Detector -> "Create sonograms in WAV folder" 2.3 09/22/2025 Trigger sensitivity now in dB
Signal levels now reported in dB
Manual heterodyne tuning now supported by finger dragging in the large sonogram history window. Tap to restore frequency scanning.
Updated help file to match app. 2.2 07/02/2025 Time expansion window now displays the frequency of the time expanded call. Big improvements to user manual. User manual now loads and is displayed the first time the app runs. 2.1 06/27/2025 Fix to time expansion when app is backgrounded - previously it could take a long time for the app to catch up after being backgrounded.
Improvement to interference suppression.
Addition of 8x and 10x time expansion 2.0 06/11/2025 Bugfix around "demo mode" and app foregrounding on iOS 12 devices.
New feature - tap in time expansion window to freeze time expansion display, which gives a bat walk leader a chance to explain nuances of bat calls to participants.
Frozen time expansion window is indicated by pulsing "ice blue" border 1.92 04/16/2025 Modified to support older iOS versions. Now runs on iOS 12.2 / iPhone 6. 1.9 04/06/2025 This version fixes a bug in audio quality that appeard on some phones, notably iPhone 12 Mini running iOS 17.5.x
Recordings are now time stamped within the GUANO metadata, not just in the file name, to help certain auto ID classifiers.
Visual feedback alerts you to a non-detected USB microphone, and to Demo Mode being engaged. 1.8 03/17/2025 Now extremely stable and reliable when the external microphone is plugged in and unplugged. On-screen messages now let you know that the app did not detect an external 384kHz microphone, and also alert you to let you know you are in Demo Mode, i.e the bats you are hearing are not live.

Export the recordings to a Mac or PC to review them using sonogram.js (from the pipistrelle deliverables package, see https://www.pippyg.com), and then visualize your batwalk in Google My Maps by exporting the .CSV generated by sonogram.js 1.7 03/05/2025 Routes audio out of the phone speakers for extra volume. 1.6 11/19/2024 Imrovements in detection, output volume, new colour options for spectrograms. 1.5 10/29/2024 New options for fast, slow or elastic timeline. Elastic view shows close-up of bat calls on far right of sonogram display, with the far left showing a compressed view, with smooth gradation between.

A "WAV prefix" can be set up per-device (Settings-> Bat Detector) so that a bat walk featuring multiple copies of Bat Detector will generate unique file names, removing the risk of file name clashes when uploading sessions to cloud-based classifiers such as the BTO Acoustic Pipeline.

All-new demo audio files, mostly recorded on a bat walk near Malmesbury, Wiltshire, UK on August 24th 2024 (International Bat Night ). A few additional files featuring good pipistrelle social calls were recorded the following night. 1.4 09/10/2024 The help file is now exported the first time the app runs, and can be found in the Bat Detector folder of the Files app.

If you are (for example) using Bat Detector in an education environment and want to use your own bat recordings for Demo Mode rather than the supplied recordings, now you can. Create a folder called Demo inside the Bat Detector folder (again, inside Files) and fill it with up to 32 recordings. These recordings need to be 384kHz, 5 seconds, 16-bit mono - it's easiest to use recordings captured with Bat Recorder. 1.2 07/13/2024 1.0 06/13/2024