2012 MacBook Air plagued by audio noise with Apple's Thunderbolt display
A driver-related bug appears to be causing progressive audio garbling and static.
A number of owners of Apple's latest MacBook Air models who have attached their systems to Apple's Thunderbolt display are noticing the system will progressively develop audio noise in the display's speakers after some use.
Apple's Thunderbolt display is not only a wide-screen display, but also includes FireWire, USB, Ethernet, and audio controllers, which are all connected to the system through one Thunderbolt port. For laptop users, especially those with the smaller screens of Apple's MacBook Air, these options make the display an attractive docking solution when using their systems in a workplace or home office.
While in this regard the display has its advantages, for some people who own the latest 2012 MacBook Air systems, the display is showing a notable audio problem when connected to these systems that starts between a few minutes to a few hours after use. In a rather lengthy Apple Support discussions thread, users are noting that once audio is played the static begins interfering with the signal, and for some the audio will eventually fade out to nothing.
This issue does not happen for all people, or at least does not happen in the same time frame. While in some cases the problem starts immediately, in others it takes a while to develop, and yet in others it does not appear to happen at all. This lack of repeatability and standardized behavior of the problem makes the root cause difficult to pinpoint. However, it is indicative of a driver error that could be from a memory leak or similar progressive rundown of resource management in the driver that affects the buffering and streaming capabilities of the driver and device.
While this problem happens periodically with audio controllers (especially external controllers), usually such problems are a rare occurrence and reconnecting the device or otherwise re-initializing the driver is enough to clear the problem. However, in this case the bug causing this behavior is exacerbated by the use of the audio controller on the Thunderbolt bus, causing it to continually crop up.
As with third-party external controllers that show this problem, users can clear this problem by unplugging and reattaching their displays, toggling between audio outputs, or pausing and resuming audio playback. As long as the Thunderbolt audio controller is being used the problem will reappear. A few users have noted that this problem seems to correspond to USB activity through the display, and have found that they can extend the duration before the static occurs by avoiding the use of USB connections on the display; however, even this only delays the inevitable static.
This problem will ultimately have to be addressed by Apple in the form of a software update, or perhaps a firmware update, and luckily Apple is apparently aware of the issue, though it so far has not officially acknowledged the problem (Apple often does this when releasing a patch for problems). For now, if you are experiencing this issue, then your best bet is to avoid using the Thunderbolt display as an audio device, and instead use the system's internal audio controller.