Bit old now did this a year or two ago but gives you an idea how it's done. I lost the decoding speach pic.. I'll try and find it and add it here. Apart from this research you will be pleased to know Facebook at building 8 are currently working on decoding speach from the brain (even know it's been done for years) and Elin Musk is working on AI which scans the RF for anomilises all exciting stuff! Anyway here it is!