Globally Disable Microphone in Big Sur?

After upgrading to ***Big Sur*** from ***Catalina***, I remarked my fan was running continuously. Opening Activity Monitor I remarked that "***com.apple.SpeechRecognitionCore.speechrecognitiond***" was chewing through CPU at 37.3%. Looking a likely candidate, and just being a bit anal about having a microphone in an ***always-on*** state, I wanted to knock that nonsense on the head. There was a microphone graphic on my screen which presented the option to "***Sleep***" which when clicked then presented the option to toggle the mic to "***Wake Up***". Clicking this did nothing: Speech Recognition nonetheless kept the fan humming and chomping through CPU cycles. After toggling every application's access to the microphone to deny access, "***com.apple.SpeechRecognitionCore.speechrecognitiond***" was still happily chomping through CPU. ***Where is a setting to toggle the microphone off at OS level in Big Sur?!?!?!***