For issues with Chromecast you can visit the Chromecast help pages to troubleshoot any issue with your Chromecast device.

You can also try rebooting your Chromecast device and the device you are casting form to see if this will bring the two back in sync.

If you are using an external speaker or soundbar then you may want to try switching to your TV's internal speakers to see if the issue is with the external device.