Android Signal analysis + some filters.

Question

Hello,

as the world cup is the main sport event and the Vuvuzelas are the most annoying sound in the world, I had an idea to remove them definitively by reading this new ( http://www.popsci.com/diy/article/2010-06/simple-software-can-filter-out-vuvuzela-whine) that told us that the sound has some frequencies at 233Hz + 466,932,1864Hz.

I have already made a lot of Android application by myself but never touching the signal analysis and filtering part, so here are a few questions, I do not ask for precise answer but maybe links and tutorial to find something to work on. I guess that a new Android phone has the CPU and power to make real-time filtering.

1) How can I intercept the sound coming from the Jack microphone - Line-IN plug- ( I plan to link my TV to my phone with Jack to Jack plug). My question is totally software and coding, I have all the wires and adapters to plug a jack into my android phone Line IN.

2) Are there some Fourier analysis librairies, may I have a look to Java libraries on the web and import them to my Android project?

I really apologize because my question seem not precise, but I think that would be something great.

Thank you for your answers.

Answer 1

Great question!

I don't see the line-in connector listed explicitly as an audio source option but perhaps you might want to start by getting data from the microphone source to get your code working, then find a way to obtain audio from the jack.

For the Fourier analysis/translation you may also consider this stackoverflow question

Answer 2

Well, if you want to filter fixed frequencies (233 hz, 466 hz, etc.) you should look also to other forms of digital eq-filtering. Doing through the FFT will use a lot of processing, and will make a real-time application became really heavy. On this website there is some directions on the mathematical ideas behind other filtering methods: http://mysite.mweb.co.za/residents/cyb00746/audiodocs/Digital_EQ.htm