Hello oli1021,
First thing to check is that your AirPods Max firmware is up to date. The current firmware version for yours is 5E135. Here’s how to find which version yours are on: Identify your AirPods - Apple Support
About firmware updates for AirPods - Apple Support -- If your's require updating, follow the steps near the top of this article.
Before you begin, make sure your iPhone, iPad or Mac is up to date:
iPhone and iPad: Update your iPhone or iPad - Apple Support
Mac: Update macOS on Mac - Apple Support
If your AirPods Max required updating, test the issue.
If you’re still hearing the “crunchy” noise after updating the firmware, or the firmware was already up to date, see if resetting them resolves the issue: How to reset your AirPods Max - Apple Support
If you’re still hearing the “crunchy” noise, please contact Apple Support: Get Support
Thanks!