How to send wav file from arduino to MIT APP and save it?

I am a beginner in MIT APP and I tried to transmit the wav file from arduino to my phone through bluetooth. The sound is recorded by microphone and stored in a sd card. But I failed to transmit this file and save it. Could you give me some suggestions about this problem?

Example to send a Base64 file from the Arduino to the app, they must be small files ~50 KB.