You can now see your Cacophony Index
As promised, the fantastic engineers at The Cacophony Project have released the first version of the Cacophony Index and you can now have a look at and a play with the numbers.
The Cacophony Index is a measure of the amount of bird song. It's a number between 0 and 100 that is calculated for every 20 seconds of recording. So for our typical 1 minute recordings, you get 3 numbers.
For example for this recording taken from my back yard around dawn there is fairly continuous chirping and so it has high Cacophony Index numbers of 69.6, 67.4, and 69.1.
The index is designed to be robust against many types of noise, such as wind, rain, aircraft engines and other common non-animal sounds.
It assumes the audio is from a recorder outdoors in a natural setting, away from non-natural sound sources, such as music, motorbikes or talking, any of which can produce very high Cacophony Index numbers in the 80s and 90s.
Some natural sounds, such as ocean waves or water dripping in a repeated pattern, will also confuse the index, so care must be taken if abnormally high cacophony index numbers are reported.
At the moment the only way you can see your Cacophony Index is by exporting your data to a spreadsheet. You do this by clicking on the export button at the top of the search results and it downloads a file that you can open in a spreadsheet.
When you open the spreadsheet there is now a column called Cacophony Index containing the 3 numbers for each recording.
We started calculating the Cacophony Index for all recordings on December 9. We will soon be processing all the old recordings, so you will have a Cacophony Index going back from when you started recording. We will let you know when this is ready.
From here you can have a play with the data and see what you can find. Here's some things I did. I converted the list of numbers which are separated by semi colons into 3 columns using the text to data functionality. I then averaged the 3 numbers for each recording and plotted it on any x-y graph.
This is pretty uninteresting, but does show the range and that there is a regular variation. I then put that data into a pivot table and looked to see how it varies over the time of day.
This is more interesting - it shows that the birds are quiet at night time and noisier during the day. This gives you some confidence that the index is working. In fact we like this so much that we are going to create a version of this that we will show in the console without having to touch a spreadsheet. Here's a mock up of what this might look like. I've added on the red labels. (Thank you Sara Coutinho, the open source contributor who created this).
I then created a daily average and plotted this.
This is also fairly uninteresting because it doesn't change. However, it is this type of graph that we think will be interesting over longer periods of time. This will allow you to see:
- how birdsong varies through the year.
- If you're trapping, is your volume of birdsong going up
- How does your index compare to someone else's?
- If your index is going down then maybe you've got some evidence that you need to do some more control.
We will eventually show this sort of information directly in the console. For now please download your Cacophony Index numbers and have a play. Let us know if you find anything interesting. If you want to start recording your Cacophony Index then grab your bird monitor from here.
A big thanks to Chris Blackbourn who developed the algorithm to generate the Cacophony Index.