Apple has rolled out iOS 6.1.4 for the iPhone 5. According to Apple it sports an “updated audio profile for speakerphone.”
To update your iPhone 5 to iOS 6.1.4, open Settings -> General -> Software Update and tap Download and Install when the update appears. You can also connect your phone to your computer and apply the update from iTunes, or download it manually at http://tinyurl.com/bebc5jb .
