Hi there madalenapereira,
If you are hearing unexpected noise from your MacBook Air, the first thing we would recommend is to ensure it is fully updated. This installs feature improvements and bug fixes that can resolve unexpected behavior like this. These steps from Update macOS on Mac show how to back up and update:
Before following these steps, it's a good idea to back up your Mac.
1. From the Apple menu in the corner of your screen, choose System Settings or System Preferences.
• If you chose System Settings, click General on the left side of the window. Then click Software Update on the right.
• If you chose System Preferences, click Software Update in the window.
Software Update then checks for new software.
• If Software Update finds new software, click the button to install it. The button might be named Update Now, Upgrade Now, Install Now, or Restart Now, for example. You might then be asked to enter your administrator password.
• If Software Update says that your Mac is up to date, then no new software is currently available for your Mac model. Software Update shows only software that is compatible with your Mac.
Once your Mac is fully updated, follow the recommendations outlined here as well: Keep your Mac laptop within acceptable operating temperatures
If this continues to occur, please provide more details on what apps or functions you are using when this happens so that we can continue to assist.
Cheers!