Great stuff! I've managed to get this working, and it does seem to be picking up some signal from the mic. The decibel level seems to be working, however, the frequency numbers are pretty erratic! Is there a (fairly) easy way of filtering the input so that it's only analysing sound over a given frequency? I noticed there is mention of a low pass filter in the code, but a high-pass would be very useful too - to eliminate the effects of low rumbly sounds. (Maybe this is why the numbers are erratic?)
Also, I spotted that the output sound levels on iOS are very much reduced once the mic has been activated - even when the recording has stopped. This doesn't seem to affect the Android version though.
thanks!