@Jenna H
Does this only happen while on a 3CX Call via Google Chrome?
First off do make sure that you are running the latest version of Google Chrome and that the OS is up to date as well. To be honest it does not sound like the issue is directly related to 3CX but here are a few more things you could check if the issue persists:
1. Check for any browser extensions that might be contributing to the issue and disable them. Alternatively you could simply test in incognito mode with all browser extensions disable, see if the issue still occurs when doing so.
2. Keep an eye on the PC's resources and check whether you have high CPU, Disk or RAM usage during a 3CX call or when generally using Google Chrome.
3. Test with a different browser such as Firefox or the new Microsoft Edge.
4. Check for any security software that may be contributing to the issue such as Antivirus or Antimalware software. You might want to consider uninstalling them at least temporarily.
5. Make sure that the issue is not due to hardware related issues such as with the microphone or speaker being utilized. Make sure that they work okay with other applications, webpages such as youtube, etc.