The only way to avoid getting this error message is to use the PlainTalk microphone. The reason for the message is the internal microphone is susceptible to feedback and noise since it is located nearby and in the same housing as the built-in speakers. The software detects that you have chosen the built-in microphone in the Sound control panel and warns you accordingly.
An option for you is to purchase a PlainTalk microphone and select the external microphone as the input source in the Sound control panel. Open the Sound control panel, select Sound In from the pop-up menu, click Options, and choose the external microphone as your source.
Using the external PlainTalk microphone gives you better speech recognition.
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