If you're playing Street Fighter X Tekken like I am on the Xbox 360, you've probably played someone online and noticed the audio coming in and out. It happens at various times throughout a match, but it does happen on a regular basis. Many were hoping that Capcom would provide a fix right away, however in a developer blog on Capcom Unity, that is not going to happen.
Street Fighter X Tekken assistant producer, Tomoaki Ayano , explained that because the netcode was designed to have four players fight each other at the same time online, and it's the netcode that is causing the sound issues. Ayano continues to say that if they were to fix the sound issues that the online play would suffer causing more lag. Of course, some commentators on the page made this point, the onilne mode is already laggy so the netcode is not doing that great of a job. We'll see if Capcom will eventually find a solution to this very embarrassing problem.
Source: Capcom Unity