So, our Warblr bird sound recognition app has been out for almost a month, and we've had many thousands of people using it and submitting bird audio recordings (thanks!). We've also had lots of great reviews in the consumer press. (Listen to this evocative piece on BBC Radio Scotland, fast-forward to 1hr 43.)
One thing which we knew was going to happen was that some people would demo it by playing back sound recordings into the mic, rather than recording actual birds. After all, sound recordings are easier to grab... What I didn't realise, from my own perspective, is that people would think this was a good way to test the app.
Playing back recordings is usually a really bad way to test the app, or any sound recognition app really, because recorded sounds differ in many many ways:
All of these things make the audio drastically different from a genuine direct recording, even though our human ears are clever enough to understand the correspondence. Yes, ideally a system would be as clever as our human ears, but that's for the future. (Note the difference from a product like Shazam, which recognises recordings but does not recognise the real live musician... interesting eh!)
Plus there's yet another aspect to consider: we make use of your location to help determine what kind of bird is likely. This is thanks to the BTO whose amazing crowdsourced bird data helps us know which birds to expect where and when. So, if you're playing a sound file that isn't native to where you are, our system is doubtful that the bird is there... and quite rightly doubtful, perhaps.
I can't emphasise enough that playing back recorded sounds is not the best way to test. We can't prevent people from doing this, of course! That's fine, but always bear in mind that you didn't test it in proper field conditions, only at your desk. You're not testing a bird recognition app if you're not testing it against real wild birds...