how do i change or eliminate the tone that occurs when i start and end speech to text in messages?

If I'm listening to music or a book on tape, and I need to send a text, I press the microphone and a really obnoxious high-pitched tone comes on. I have to remember to turn off all the sounds 4 it to not make that sound. And when it's finished with the text when I'm finished speaking, it turns off the microphone and It makes that horrible tone again. I want to eliminate that tone.

I this is on a Nexus 6