So many files!
All the data that goes into Bat Detective has been collected by many wonderful volunteers around the world as a series of individual recordings, each 90 minutes long. Each of these recordings contains thousands of the individual snippets that you see on bat detective. As the bat calls are ultrasonic, we use time-expansion to record them. A specialised microphone records ultrasonic information for a short period (320 ms) and then slows that sound down and plays it into a recorder (slowed by 10x, giving a 3.2 second recording). This results in a long recording that contains thousands of small 3.2 second snippets of audio.
Chopping all this data up has really tested some of our desktop computers. Once you consider that we have 1000s of events, each containing thousands of snippets (and each snippets has a sound file and a spectrogram image), you can see that we very quickly have a lot of files! I recently discovered that copying 4.5 million tiny files to a usb disk can take a while!
We’re really excited about getting people involved in Bat Detective, because many of these snippets contain calls from individuals bats, and individual researchers finding them manually would be impossible! Having everyone help us find these calls not only allows us to try and identify the species making those calls, but will also allow us to try and generate methods to automatically detect bats, insects and other noises in these data.