Diagnosis
This is usually not a broken mic, but audio interference. The wireless signal carrying the audio is getting corrupted, often because the parent unit and camera are on the edge of their range or there's something causing electrical noise between them.
How to Fix It
First, adjust the placement. Move the parent unit closer to the camera's location, even temporarily, to see if the static clears up. Ensure neither device is right next to a cordless phone base, a microwave, a large power transformer (like for a monitor), or a dense metal object. Second, on the parent unit, go into the audio settings and try adjusting the microphone sensitivity down a notch or two. High sensitivity can amplify background interference.
If That Didn't Work
The issue could be with the camera's transmitting hardware. Try changing the channel on your router (as described in the disconnection fix). A cleaner Wi-Fi environment can improve audio quality. Also, power cycle both the camera and the parent unit by unplugging them for a minute.
Heads Up
Test the audio using the Motorola Connect app on your phone. If the audio is also crackly there, the problem is with the camera's transmission or microphone. If it's clear on the phone but crackly on the parent unit, then the issue is with the parent unit's speaker or its specific wireless reception. That helps narrow it down for support.