Some iPhone and iPod touch users have reported an issue in which music and other audio playback exhibits a crackling noise after the update to iOS 4.1. The problem is more likely to occur when the device is connected to an amplified sound system, such as a car audio interface or a speaker dock, via the dock connector.
Anecdotal evidence suggests that the iOS 4.2 update, due in November, may resolve this issue. In the meantime, here are some potential fixes:
Turn off Bluetooth. It appears that some instances of this issue may be caused by the iPhone or iPod touch’s inadvertent switch to Bluetooth audio. As such, you may be able to obviate the problem by temporarily turning off Bluetooth. Navigate to Settings > General > Bluetooth and slide Bluetooth to “Off.”
Restore as new phone using DFU. Some users have reported that performing a DFU restore resolves this issue. To perform a DFU restore, follow these steps:
- Backup your phone and preserve data. Follow the steps in this Apple Knowledge Base article to transfer your purchases and backup your iPhone.
- Put iPhone into DFU mode. Connect your iPhone to your computer and open iTunes (if it doesn’t open automatically). Hold down both the top (sleep/wake) and home buttons for exactly 10 seconds, then release the top (sleep/wake) button but keep holding the home button until iTunes displays a message stating that a phone in recovery mode has been discovered.
- Restore. Press the restore button and allow the phone to complete the restoration data. After it is done, select setup as a new phone.