On my 5s with 8.3, One day voice dictation was working fine, the next it's not. If I talk into the phone for dictation, the wave pattern looks like it's hearing the words, I hit done..the little circle spins for a bit, then nothing. Happens over wifi or cellular I've tried with headphones, no. I've tried talking into both mics, nope. I've done tests to check the front facing mic...it's fine. I checked the back mic, it's fine. I've restarted. I've disabled dictation and re-enabled it. I'm out of ideas right now. I can't think of any changes I've made that would have done anything...I upgraded my iMac to El Capitan, so there's the convergence stuff happening now, but first time I saw this, I wasn't at home.