If you have speakers plugged in as well, it may not immediately show your Kraken as the default device. You need to go to the sound options and change it accordingly. If it's not that, try switching it to another USB port and see if that fixes the issue.
As for the buzzing noise, that's a tough one to diagnose. What are your settings in Synapse? Do you have the sensitivity turned way up? I have mine set at 35 and it works great with no issues. I've also had mine for more than a year.