Hi I'm creating an app whereby a user chats to an NPC, the NPC is powered by Open AI. I want my app to automatically detect when the user speaks, and do stuff with the microphone input (send the audio to openai for speech to text transcription etc) and detect when the speech has stopped. Meta's Wit AI can capture mic audio and transcribe it but it offers no automatic voice detection feature, you have to press a key/button first to let it know you're speaking, I don't want that. Can anyone point me in the direction of what I want i.e. an existing software solution etc?