Hi Sam,
There is no difference between newVoiceRecorder("recorder") and newMediaRecorder("recorder", "audio"), so unfortunately MediaRecorder won’t provide you with a way to detect speech any more than VoiceRecorder.
You could probably listen for a sharp rise in the signal’s volume using the AudioContext javascript API, but it’s a little advanced (it also turns out to be quite unreliable on Safari, which no one on the Internet–except me–seems to have complained about so far…) and it doesn’t necessarily indicate speech, for example it could correspond to a mug spilling on a desk (though that would most likely be accompanied with vocal complaints too).
Not sure I’d have the time to implement that function, but if you’re comfortable with javascript or know someone who is, I’d be happy to help
Jeremy