title: issue when running the sample SpeechToText_WPF_sample
body: <p>When we try running the sample SpeechToText_WPF_sample (<a href="https://github.com/Azure-Samples/Cognitive-Speech-STT-Windows" rel="nofollow noreferrer">https://github.com/Azure-Samples/Cognitive-Speech-STT-Windows</a>) with a free subscription key, somtimes it works but frequently we are blocked with :</p>
  
  <p>--- Start speech recognition using microphone with ShortPhrase mode in en-US language ----
  --- Microphone status change received by OnMicrophoneStatus() ---
  ********* Microphone status: True *********
  Please start speaking.</p>
  
  <p>and after a few minutes (maybe 1 or 2 minutes) we get this message (and all radiobutton are disabled) :</p>
  
  <p>--- Microphone status change received by OnMicrophoneStatus() ---
  ********* Microphone status: False *********</p>
  
  <p>i don't think its a network problem because when i test with a bad SubscriptionKey i get instantely this error message :</p>
  
  <p>--- Error received by OnConversationErrorHandler() ---
  Error code: LoginFailed
  Error text: Transport error</p>
  
  <p>could you help us please ?</p>
  
  <p>Regards,</p>